The BSA A7-A10 Forum

Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: AdrianJ on 03.11. 2019 14:11

Title: More problems starting.
Post by: AdrianJ on 03.11. 2019 14:11
I'm at my wits end here.
Since my recent problems with the clutch jamming can't get any life out of the engine - the bike started well before that.
I've checked the valve timing - though I appreciate it can hardly go wrong.
Set the ignition timing 3 times. 11/32 btdc.
Dead -  no sign of anything apart from a very occasional (every 30 or more kicks) detonation in the exhaust.
Last time I forgot to remove the wedge advancing the auto - advance/retard unit and I consistently get it kicking back and spitting through the carb!
Take the wedge out and it's dead again.
It looks fairly obviously like a timing problem - but what. I would have thought that if it is close enough to kick back when over advanced there should be some life when retarded.
I'm setting the points when they are at about 10 o'clock looking at the end of the magneto and I have the rear/bottom pick up connected to the right hand cylinder.
Any ideas gratefully received.
Adrian
Title: Re: More problems starting.
Post by: AdrianJ on 03.11. 2019 14:15
Just realised I never introduced myself even though I've been posting here for well over a year.
I'll put an introduction in the appropriate section.
Adrian
Title: Re: More problems starting.
Post by: Triton Thrasher on 03.11. 2019 14:16
Did you try reversing the plug leads?

Is the slip ring clean?

I don’t mean the cam ring.
Title: Re: More problems starting.
Post by: AdrianJ on 03.11. 2019 14:26
Hi Triton Thrasher,
Yes - tried reversing the plug leads.
Mag has just been rebuilt and was working fine but will check slip ring.
I seem to have a good spark.
Adrian
Title: Re: More problems starting.
Post by: bikerboy on 03.11. 2019 14:59
The timing is obviously out so I suggest you reset it again and this time note what stroke you time it on so that there is no chance of the leads being on the wrong way round. That will eliminate one thing for a start.
Title: Re: More problems starting.
Post by: Triton Thrasher on 03.11. 2019 15:03
Do you check the timing after you think you’ve set it?

How do you check it?
Title: Re: More problems starting.
Post by: groily on 03.11. 2019 15:11
Just for the sake of clarity, when the opening point fibre heel is on the lower cam lobe - ie the points are around your 10 o'clock position - then the gearbox side (rear) pick-up is being fired.
Which means, if you have the rear pick-up connected to the rh plug, you need the rh cyl to be the one on the compression stroke, both valves shut.
Also, don't want to teach grannies etc, but make dead sure the piston is truly on the 'up' stroke, and remember the cb assembly goes clockwise looking at it straight on. I think that is OK, or the points wouldn't be opening at 10 o'clock  . . . but mags have been beautifully set up with the points just opening on the closing ramp of a camring before now! And pistons have been ever-so-carefully positioned perfectly on the wrong side of TDC!

 
Title: Re: More problems starting.
Post by: AdrianJ on 03.11. 2019 15:18
Triton Thrasher,
 That sounds like a mistake - I've been relying on it being correct.
The only way I can think of to check it is to set the piston at 11/32 btdc, rotate the mag to advance it and check the gap?
How would you check the timing.
Will do this again tomorrow am.
Biker Boy - I know which stroke and cylinder I'm on from checking the operation of the rockers.
This is all subject to me not doing something stupid like timing it after tdc..
I'm timing the RH cylinder on the upstroke after the downstroke with the inlet valve open.
Rotating the engine with a socket on the crankshaft, clockwise looking at the timing end of the crankshaft to find tdc, backing off (anticlockwise ) and then going forward again to 11/32 btdc.
Adrian
Title: Re: More problems starting.
Post by: AdrianJ on 03.11. 2019 15:21
Hi Bill,
 Yes - that's how I have it set up.
I know the valves are closed because I have the rocker covers off and can see and feel the tappet gap.
I'm using an auxiliary petrol tank, so that I don't keep reassembling.
I've also got the timing cover off.
Adrian
Title: Re: More problems starting.
Post by: bikerboy on 03.11. 2019 15:28
Biker Boy - I know which stroke and cylinder I'm on from checking the operation of the rockers
------------------------------------------------------------------------------------------

Yes but are the points are at the top or the bottom to make sure the right lead goes to the right plug?
Title: Re: More problems starting.
Post by: AdrianJ on 03.11. 2019 15:44
Yes but are the points are at the top or the bottom to make sure the right lead goes to the right plug?
________________________________________________________________________________
Points are at the top - 10 o'clockish, which should mean that the rear pickup is firing - this is connected to RH cylinder which is near the top of its compression stroke .
I've checked and rechecked this.
Adrian
Title: Re: More problems starting.
Post by: groily on 03.11. 2019 15:47
I was doing an edit while you were tapping away just now Adrian - I'd pushed awrong tit and it sent itself before I wanted it to.

But, if you are happy that
a) the piston is btdc not atdc and in the right spot,
b) the rh side is under compression, with
c) the points heel just onto the lower ramp, thus
d) firing the rear/ gearbox pick-up, which
e) is connected to the rh plug, atd wedged open etc etc  . . .

the darn thing should work!

Could it be something other than a sparks problem?
Title: Re: More problems starting.
Post by: berger on 03.11. 2019 16:01
I went to the pub *countdown* *beer* AdrianJ you could try a tiny  bit of petrol down the plug holes and see if you get a few fires out of it
Title: Re: More problems starting.
Post by: AdrianJ on 03.11. 2019 16:07
Will do Berger.
Not going to pub, but going to have a beer and a whisky after a hot bath.
Adrian.
Title: Re: More problems starting.
Post by: Triton Thrasher on 03.11. 2019 17:46
It is common for the timing to move when you tighten the pinion onto the armature.  So, you must check the timing after setting it.

Check it by slowly rotating the crankshaft forward until the points just lose their grip on the fag paper. 

Mark the stick in the plug hole, then continue to turn the crankshaft, to TDC.  Mark the stick again and measure the distance between the marks.

Title: Re: More problems starting.
Post by: AdrianJ on 03.11. 2019 17:55
OK will try tomorrow.
Thanks,
Title: Re: More problems starting.
Post by: Greybeard on 03.11. 2019 18:00
OK, I see what you wrote, but, when I have timed the wrong side, so the wrong plug is firing, I have had the occasional pop in the silencer. Your description sounds the same.
Title: Re: More problems starting.
Post by: Swarfcut on 03.11. 2019 18:14
Adrian. The reason it won't go is the holy trinity of mechanical, electrical and carburation are not in harmony. One of the buggers is playing up.

 Mechanical...Do your basic checks, timing gears correctly set up, valves opening and closing, tappets set OK.

 Ignition.....Timed or not,  as long as the maggy is driven, you should get sparks, so check this with a plug lead sparking to earth. The trick then is to get the spark to the right time and place.

  With a wooden pencil or meat skewer feel down the plug hole and rotate the crank forwards until the piston reaches Top Dead Centre, and mark the wood level with the edge of the plug hole. Remove the stick, mark it above the first mark  with the chosen distance for the advance specified.  Reverse the crank, put stick in hole, turn crank forwards until top mark on the stick is level with the edge of the plug hole. This sets the crank at the firing position, one cylinder will be on compression, both valves closed, and the points (auto advance wedged open) just opening.

 Look down the magneto at the slip ring. The pick up hole  with the slip ring brass segment visible is the one on the firing stroke, so connect this pick up to the cylinder on compression. Leave the points cover off to eliminate any obscure fault earthing the maggy.

 You may have to adjust the auto advance on the  magneto armature taper if it wildly out. As a temporary measure, opening the points gap will advance the timing.

 Carburation. Do as Bergs suggests, a good splosh of fuel down the plug holes, or better still a good spray of "Start Yer B***rd" If it fires but then cuts out you can work your way through the fuel system.

 I start reluctant mowers with a spray of carb cleaner, barbecue lighter, brake cleaner or even WD. All have high volatile solvent content and give the motor a chance to fire a couple of times, enough to start it drawing fuel.

Whoops, further posts  added while I was typing this, so some tips may be repeated.

 Swarfy.
Title: Re: More problems starting.
Post by: Klaus on 03.11. 2019 22:03
Hi Adrian,

I still remember you had the timing side cases off. My be the idlerpinion is also slipped off? Are you sure the valve timing is right?
Its still a guess, you can set the ignition right but the engine wont start with a wrong valve timing.

cheers Klaus
Title: Re: More problems starting.
Post by: RichardL on 04.11. 2019 02:29
Hi Adrian,

I still remember you had the timing side cases off. My be the idlerpinion is also slipped off? Are you sure the valve timing is right?
Its still a guess, you can set the ignition right but the engine wont start with a wrong valve timing.

cheers Klaus

Not to mention the possible collision of valves with pistons, I believe.

Richard L.
Title: Re: More problems starting.
Post by: AdrianJ on 04.11. 2019 14:16
RichardL and every one else,
I've just had the inner timing case off again.
It's difficult to see if the the valve timing is OK as the marks only line up one every "lots" of revolutions, so I've realigned everything (dot and dash marks).
As the engine hasn't moved I also know that I'm at tdc after the compression stroke on the RH cylinder.
Ran out of time today. Tomorrow will check and retime the ignition (and make sure which pickup is firing which cylinder) and then try to start again.
Adrian.
Title: Re: More problems starting.
Post by: bikerboy on 04.11. 2019 16:32
Is it possible that the valve timing marks are wrong

As in somebody having whacked a mark accidentally and you are lining up to that and not the proper mark?

I have had that on another bike in the past, I wont mention the make :)
Title: Re: More problems starting.
Post by: AdrianJ on 04.11. 2019 17:41
I doubt it really bikerboy,
Firstly they look like proper stamped marks.
Secondly - it was running fine till 2 weeks ago on those same marks.
I'll know more when I've checked and retimed the ignition tomorrow.
If that doesn't work I'll try steadily advancing the ignition till it runs.
Adrian
Title: Re: More problems starting.
Post by: AdrianJ on 05.11. 2019 15:40
Losing it completely now.
Reset valve timing - also they seem to be going up and down at roughly the right times and in the right order. Took idler pinion off and set cam and crankshaft to dot and dash.
Reset ignition timing then checked it again - to the accuracy of my pencil marks it is between 5/16 and 3/8 btdc so I'll believe it's 11/32.
Tried fuel in the bores - got a bang after a few strokes, but I think it was in the exhaust.
Used quick start on carb and each cylinder - nothing.
I have a spark.
Plug caps seemed a bit loose so I wrapped some aluminium foil round the plug end.
I have ordered a cheap compression tester, so I 'll see what that says.
Can't really see inside the bottom pick up hole but top/front hole does not show brass when the timing is set.
Got to leave it now for a few days - under matrimonial pressure to do other things. Hope to be back to it next Monday. I'll have the compression tester by then.
Adrian
Adrian.
Title: Re: More problems starting.
Post by: Billybream on 05.11. 2019 16:10
Try swopping the HT leads over before you dig any deeper, now give her a good tickle until you get a very wet finger, open the throttle a little and give her a good kick.
He's praying for you!
Title: Re: More problems starting.
Post by: Greybeard on 05.11. 2019 17:29
...matrimonial pressure to do other things...
...I'll have the compression tester by then.

I didn't know you could measure that :)
Title: Re: More problems starting.
Post by: groily on 05.11. 2019 17:38
Can't really see inside the bottom pick up hole but top/front hole does not show brass when the timing is set.

Which is correct if you're setting the rh cyl, on the compression stroke, connected to the rear pick-up with the points at your 10 o'clock and the fibre heel at about 4-5 o'clock.  The brass only covers about 90° of the track the brushes run on.

If the thing ever ran before (??), then unless you've had the head off or 'done something' there should be enough compression to make it go again. And if you can feel it on the kickstart, I would bet there's enough to get it going even if there be minor devils lurking within.

You say you have a spark  . . . If you take a plug cap off, and hold the bare lead close to the cyl head while kicking the engine over, is it a solid  spark capable of leaping a quarter inch with impunity? Or a pathetic apology for a thing that needs near darkness to be seen? If the former, no worries. If the latter, then you may have a problem.
Title: Re: More problems starting.
Post by: AdrianJ on 05.11. 2019 18:21
Groily,
It ran two weeks ago when the clutch jammed. I slackened off the barrel bolts to check that the pistons weren't seized, they weren't and I retightened everything. I can feel compression on the kickstart.
I've had the plugs out and I get a good spark earthing them to the head.
I'm convinced I'm doing something stupid like timing on the wrong stroke or after tdc.
The crankshaft does rotate clockwise viewed from the timing side doesn't it? It looks like it when I use the kick start.
Adrian
Title: Re: More problems starting.
Post by: Swarfcut on 05.11. 2019 19:14
C'mon Adrian, finger down the plug hole, push the kicker, feel the compression start to build. In with the stick, find TDC on compression. Back it off, measuring stick in again, move crank forwards to the firing point on the stick. That's it, crank set...just match the maggy to that.

 Swarfy.
Title: Re: More problems starting.
Post by: chaterlea25 on 05.11. 2019 19:44
Hi Adrian and All

A possibility is that a pushrod has jumped out of a follower or rocker as a result of lifting the barell  *????*
As others have found out for some reason or other the pushrod ends can pop out and sit on the edge of the follower

John
Title: Re: More problems starting.
Post by: Triton Thrasher on 05.11. 2019 19:48

The crankshaft does rotate clockwise viewed from the timing side doesn't it? It looks like it when I use the kick start.
Adrian

The crankshaft rotates the same direction as the wheels.
Title: Re: More problems starting.
Post by: AdrianJ on 05.11. 2019 21:32
As you can see I'm clutching at straws.
Tritonthrasher - that's what I thought.
John, I've had the rockers off and seated everything properly (i think). I'll check my tappet clearances again.
Swarfy, that's just what I did except I used the rockers to tell me I was on the compression stroke.
I've checked the timing with a stick and it is correct to within 1/32"
Adrian.
Title: Re: More problems starting.
Post by: trevinoz on 05.11. 2019 21:38
Have you checked your pilot jet?
Title: Re: More problems starting.
Post by: AdrianJ on 05.11. 2019 22:45
Yep, just replaced the needle it's currently at 2 turns out. Though it's been 1 1/2 most of the time
When i took the carb off I squirted carb cleaner down it and it comes out of the small hole just in front of the manifold  *conf*
Title: Re: More problems starting.
Post by: duTch on 06.11. 2019 00:14

 But have you checked the *actual*  pilot jet-- I think the needle is not related much to it....
 It is possible for otherwise good or new plugs to break down under compression, so check as broil suggests

 It's easy to time it so the bottom rear pickup hole fires the left plug- I never remember which is 'normal' so usually do whichever is best at the time..*conf2* but after this I may remember... so definitely worth switching the leads (again?)....

 Good luck with the matrimonial compression
Title: Re: More problems starting.
Post by: Triton Thrasher on 06.11. 2019 07:01
Have you checked your pilot jet?

Good point, in cases of hard starting.

And not fixable by squirting stuff into holes in the carb.
Title: Re: More problems starting.
Post by: WozzA on 06.11. 2019 08:35
Hows the float level?  I had trouble with a low level & the pilot jet couldn't pick up the fuel to start...   if it starts ok with a squirt of Start ya Ba$tard or similar check the float level.
Title: Re: More problems starting.
Post by: Rudgeman on 06.11. 2019 11:28
After I had refurbed the atd recently I had some difficulty setting the timing. You might find my learning interesting.

First I didn't want to remove the chaincase and fit a timing disc. So I made a bracket that bolts onto the exhaust rocker spindle to hold a dial gauge with an extended and slightly bent rod to go down the plug hole onto the piston. I could then measure piston position before tdc accurately. I was aiming for 5/16 (0.313").

Next I jammed a socket on the crank nut and used a long torque wrench handle so I could turn the engine over by reaching across when standing on the left of the bike.

Finally I bought an electronic buzzer device that tells me when the points open. Wow, I wish I'd had one of these when I was a kid.

With all that in place I thought it should be easy - it wasn't. With the crank at the right angle, the atd wedged advanced and the points just opening, I gently tightened the atd nut. When I turned the crank back a bit and then forward I found the timing was miles out. I hadn't noticed anything move when tightening, but it must have. In the end I repeated this many times, got a consistent error, averaged it and then deliberately timed it to offset the error. Bingo - the timing was very close (about .310"). Of course I then checked the other cylinder and found it was about .340 so I had to do it all over again to get the average of the two about .313".

If only the mags had slotted holes it'd take a lot of the hassle out of it.

Good luck,
                   R
Title: Re: More problems starting.
Post by: RDfella on 06.11. 2019 12:10
Rudgeman - getting creep when tightening onto a taper is often annoying. As you say, the only answer is to judge the creep and stert by an offset amount to hopefully end up in the right place. Manual advance, anyone?
Title: Re: More problems starting.
Post by: BSA_54A10 on 06.11. 2019 12:19
Fuel, compression, spark, the holy trinity
1) Are the spark plugs getting wet ?
If they are wet, get some nice new one as modern fuel ( which is not petrol ) is conductive at cylinder compression.
2) with nice new plugs tip about 1/8th teaspoon of FRESH fuel down each plug hole
Do the plugs up finger tight and give it a few kicks

IF it goes bang or bang bang bang bang then the timing is OK and you have a carb or valve problem

3) spray some carb cleaner down the throat of the carb and give it a good kick or three
If the engine goes bang or multi bangs then the valves are OK and you definately have a carb problem

4) if you get nothing then you have a spark problem

Are you using proper solid wire HT leads.
People fit car type graphite dust in fiberglass weave  leads which can break down

If you can get it to fire with carb cleaner down the carb throat, continue giving it very short shots of carb cleaner while giving it throttle as well.
If it does not respond to throttle once started then your fuel has gone off.

Modern fuel is basically low grade fuel oil with a touch of aromatics so the engine can start when cold.
The aromatics vapourise at room temperature to form the gas that burns in your cylinder to start a cold engine as only gasses burn.
Once the engine get hot it will boil the heavier fractions into gasses so the engine can run.
If you have had an open top tin of fuel suspended above your bike for a week or two it could very well have gone stale so can not START.
Thus the short shots of carb cleaner down the carb throat to build a little heat in the engine to vapourise the fuel ( which is not petrol ).
Keep them very short as the engine will knock a little as the CV of carb cleaner is a lot higher than normal fuel.
Title: Re: More problems starting.
Post by: BSA_54A10 on 06.11. 2019 12:23
Rudgeman - getting creep when tightening onto a taper is often annoying. As you say, the only answer is to judge the creep and stert by an offset amount to hopefully end up in the right place. Manual advance, anyone?
The answer is lapping the tapper with some fine abrasive like Brasso.
If the tapers are in good condition they do not creep.
Ham fisted mechanics do the taper up way too tight which puts a ridge on the taper which prevents it locking as readily as it should
In theory a light thump form the bottom of you palm should be sufficient to lock the taper.
Title: Re: More problems starting.
Post by: RichardL on 06.11. 2019 12:40
Adrian,

Here is an obscure thing you could check. Check to see if you live around the corner (or somehow close by) one of our other members, maybe even one of those offering help here. Of course, that could be hard for you to check, but anyone around West Yorkshire who happens to be reading this might reach out to you to pin down proximity. These second helping eyes, ears and hands might just do the trick.

Richard L.
Title: Re: More problems starting.
Post by: Greybeard on 06.11. 2019 13:44
I suggest leaving the bike alone for a week or so. When you come back to it it the problem will be obvious.
Title: Re: More problems starting.
Post by: lawnmowerman on 06.11. 2019 13:46
Adrian,

Here is an obscure thing you could check. Check to see if you live around the corner (or somehow close by) one of our other members, maybe even one of those offering help here. Of course, that could be hard for you to check, but anyone around West Yorkshire who happens to be reading this might reach out to you to pin down proximity. These second helping eyes, ears and hands might just do the trick.

Richard L.

Agree Richard. Nothing like a second pair of eyes to spot obvious (to someone else) errors.

Jim
Title: Re: More problems starting.
Post by: AdrianJ on 06.11. 2019 15:43
Thanks again for all the advice folks.
I have to leave it alone now till Monday. So I'll take Greybeard's advice.
The fuel is about 3 weeks old - I'm going to get some fresh on Monday.
Unless I've done something stupid (always a possibility) the timing is correct to within 1/32".
If fresh fuel doesn't work - I'll use a buzzer to time it.
If all this fails I'll start looking for fresh pair of eyes.
Title: Re: More problems starting.
Post by: duTch on 06.11. 2019 22:48
 
Quote
........If only the mags had slotted holes it'd take a lot of the hassle out of it...

 It can, and has been done  *work*
Title: Re: More problems starting.
Post by: Greybeard on 07.11. 2019 09:20
That's another mod for the list
Title: Re: More problems starting.
Post by: coater87 on 09.11. 2019 00:17
That's another mod for the list

 

 This single change could potentially save hours and hours of frustration over the course of a bike owners life.

 Lee
Title: Re: More problems starting.
Post by: BSA_54A10 on 09.11. 2019 09:48
Well I have been using piston stops for a long while when I set timing.
Find the right advance then screw a bolt down the plug hole till it touches the piston.
Title: Re: More problems starting.
Post by: lawnmowerman on 09.11. 2019 11:10
Well I have been using piston stops for a long while when I set timing.
Find the right advance then screw a bolt down the plug hole till it touches the piston.

...........but don't forget to take it out again - a problem for us with advancing years  *conf2*

Jim
Title: Re: More problems starting.
Post by: Joolstacho on 10.11. 2019 23:26
I seem to remember some years ago, alloy mag pinions with elongated mounting slots for fine adjustments.
Had a separate centre section with the taper mount, and an outer gear section that bolted to that. (Perhaps I dreamt it, or maybe it was for Velos).
Title: Re: More problems starting.
Post by: BSA_54A10 on 11.11. 2019 12:03
Well I have been using piston stops for a long while when I set timing.
Find the right advance then screw a bolt down the plug hole till it touches the piston.

...........but don't forget to take it out again - a problem for us with advancing years  *conf2*

Jim

Funny you should mention that  *red*
Title: Re: More problems starting.
Post by: muskrat on 11.11. 2019 18:41
G'day fellas.
The slotted mag mounts duTch mentioned  is in this thread. https://www.a7a10.net/forum/index.php?topic=13132.msg105254#msg105254  Well done Richard "orabanda".
Cheers
Title: Re: More problems starting.
Post by: AdrianJ on 13.11. 2019 16:06
Starting to get somewhere. Compression tester arrived.
LH cylinder 100psi, RH cylinder 20psi.
Got to find time now to get the head off and see what's happening.
I lost the nipple off the throttle cable a while ago, thought it came out the bell.
I'll find out early next week.
Adrian.
Title: Re: More problems starting.
Post by: lawnmowerman on 13.11. 2019 16:24
Now we are getting somewhere!
Before you remove the head it may be worth squirting a little thick oil down the faulty plug hole then try it again. If it improves then you know you may be looking at faulty rings / bore. If it does not improve then it points towards valves (bent?), head gasket and rocker clearances.
Valve timing should be ok if you are getting good compression on one cylinder.

Jim
Title: Re: More problems starting.
Post by: AdrianJ on 13.11. 2019 18:43
Thanks Jim,
I'll try that, but I bet it's a stuck valve.
Adrian.
Title: Re: More problems starting.
Post by: muskrat on 13.11. 2019 19:01
G'day Adrian.
I agree, a bent/non seating valve. You'll probably find the tappet clearance has grown on the faulty one.
Cheers.

ps: When checking compression the throttle must be held wide open and a good few compression cycles {(I do 10) then need a beer}.
Title: Re: More problems starting.
Post by: Duncan R on 13.11. 2019 22:50
Starting to get somewhere. Compression tester arrived.
LH cylinder 100psi, RH cylinder 20psi.
Got to find time now to get the head off and see what's happening.
I lost the nipple off the throttle cable a while ago, thought it came out the bell.
I'll find out early next week.
Adrian.
Careful with that tester, is a cheapo one of EBAY? I used one and it gave random readings leading me to believe that one cylinder was way down on compression and there was nothing wrong. This is quite common with these cheap testers
Title: Re: More problems starting.
Post by: AdrianJ on 14.11. 2019 07:49
Yes it is a cheap tester, but the readings are consistent.
Adrian
Title: Re: More problems starting.
Post by: muskrat on 14.11. 2019 08:54
G'day Adrian.
Is it a screw in or just a hold over the hole type?
Cheers
Title: Re: More problems starting.
Post by: AdrianJ on 14.11. 2019 09:48
Screw in and it gives repeatable results.
Adrian
Title: Re: More problems starting.
Post by: groily on 14.11. 2019 10:09
And if it repeatedly shows that very low reading one side, it probably is the problem. And likely something to do with lifting the barrels (or moving the idler pinion) I suppose, if a valve's bent, as Chaterlea John posted. Has to be something 'new' because you say it ran OK before the primary drive locking-up problem.
It doesn't quite stack up with your 'compression on the kickstart' from earlier on  . . . but that can be hard to get a good feel for sometimes.
Here's hoping you've got to the bottom of it now.
Title: Re: More problems starting.
Post by: AdrianJ on 14.11. 2019 10:18
Bill,
I think I must just have been feeling compression on the one cylinder from the kickstart, and not noticed it was every other stroke.
Adrian.
Title: Re: More problems starting.
Post by: Duncan R on 15.11. 2019 10:01
Check your pushrods are located in the right rockers - I had major issues staring after a rebuild, checked everything carb, sparks , timing. Somehow the pushrods had located in the wrong rockers  so putting the valve timing out. Was told it couldn't happen but it did. I reset the pushrods and the bike started straight away.
Title: Re: More problems starting.
Post by: AdrianJ on 15.11. 2019 11:27
Ta, I wondered about that. I'll be checking them early next week.
Title: Re: More problems starting.
Post by: AdrianJ on 21.11. 2019 15:32
Might be getting somewhere at last.
Oil in the bore improved the compression a bit.
Took head and barrels off - valves are fine.
Pistons and rings are odd.
Two photos the first shows the rings on the left piston - good compression.
The second has its rings stuck in the grooves - the low compression right cylinder.
Also there is a little scoring on the front and back of the piston skirt as can be seen in the photos.
Any thoughts?
Adrian
Title: Re: More problems starting.
Post by: lawnmowerman on 21.11. 2019 17:10
Not sure if it's the pic but that ring gap looks a bit tight on the second pic - almost non existant! Could it have been set incorrectly (or not at all) and the rings have expanded slightly more than the cylinder and scoured the bore?
Maybe the wrong rings have been fitted - you could check the sizes against the other side.
My Sunbeam S7 uses A10 rings and I had to take quite a bit off to get the correct gap.
If they have stuck when hot it may explain the lack of compression when they have cooled down and not expanded back to the bore size. The oil down the bore would have compensated somewhat and increased the compression reading.

Jim
Title: Re: More problems starting.
Post by: RDfella on 21.11. 2019 17:17
I'm with lawnmower - the piston appears to have lightly seized, but far from enough to trap rings - so do the rings have sufficient clearance, or are they the wrong ones? We hear about people changing rings to better quality ones - could this have unforseen consequences? And is that 2nd ring the right way up?
Title: Re: More problems starting.
Post by: AdrianJ on 21.11. 2019 17:38
Hi All,
The pistons came with rings on and according to the supplier correctly gapped.
They are happy to see me so I am visiting them on Monday with piston and barrels.
I'll keep you all informed of the outcome.
Adrian.
Title: Re: More problems starting.
Post by: Triton Thrasher on 21.11. 2019 18:29
When recently installed pistons seize, the first likelihood is insufficient bore clearance.

Having the timing all over the place can do it too.
Title: Re: More problems starting.
Post by: RDfella on 21.11. 2019 18:54
Adrian - to avoid confusion, I was referring to the land clearance, not end gap. And as the seizure is miniscule (whether insufficient bore / piston clearance or whatever) in my view it's way insufficient to cause rings being trapped.
Title: Re: More problems starting.
Post by: Swarfcut on 21.11. 2019 20:09
 Adrian.  The original rings were plain compression rings and a single slotted oil control ring.  Your set looks to have the more modern development of a three piece oil ring, consisting of two rails and a spring loaded spacer.

 Looks to have had a partial seizure, and smeared the skirt enough to trap the rings. Carefully removing the rings from the piston and gentle work with a craft knife and a fine file should restore the grooves. Maybe better to let the supplier take the risk and take them along as they are.

 Then its a case of examining carefully what you have, bearing in mind they may be the wrong rings for the aftermarket pistons supplied, yet correct for the OE pistons.
  The rings should have a gap when placed squarely in the bore, size of the gap is in the literature. The rings also need to fit snugly in the piston grooves, with no up and down slop. When pushed to the back of the groove, they lie below or level with the face of the piston, never proud of the face.

 Here are a few things about piston rings in general....

 Depending on the brand, all the compression rings may be identical, or a pair of top, and a different pair of second rings.

 Compression  rings can have a tapered, plain or barrel profile. If they have a tapered periphery,  they will be marked "TOP", so the narrow of the taper is fitted closest to the piston crown.

 The  compression rings on some sets have a top ring which has a stepped upper outer edge. This is a "ridge dodger" type, designed to avoid the wear ridge at the top of the bore when the old pistons are re used in the existing worn bore and just the rings are replaced. Once again marked "TOP."

  The second compression ring sometimes comes  as a "Napier Scraper", this is a a profile on the underside of the ring which acts to clear the oil film from the bore as the piston descends. Again marked to ensure correct assembly.
  As RD notes, the second ring looks a bit strange, so may be in the wrong groove, or fitted upside down. You need to lay them out as they come off and examine closely.

 Get the supplier to measure your bore, and the piston skirt diameter just below and at right angles to the pin. The difference should be the running clearance noted in the specifications. Also measure the compression ring thickness. This should match the  piston groove with a minimum clearance, just enough to allow the ring to move freely and exert pressure against the bore.


 On a broader note, anyone remember those remarkable "Cords Piston Rings"? Usually very successful in transforming knackered worn pistons and bores into as new compression with  nil smoke and oil consumption.  They were dished and cupped spring segments that produced amazing results.

 

Swarfy.
Title: Re: More problems starting.
Post by: rayjay on 21.11. 2019 20:10
Rings should be gapped in the bore before fitment to the piston, if they have not then they could nip up sufficiently enough to raise burrs that could cause them to stick in the ring grooves.  May be worth taking one off of the piston and trying it in the bore
Title: Re: More problems starting.
Post by: AdrianJ on 21.11. 2019 20:33
Swarfy and Rayjay.
You are correct about the oil ring.
These compression rings are supposed to have a barrel profile.
I will ask the supplier to remove the rings, which are certainly stuck solid in the grooves with no gap.
I'll know a lot more on Monday.
Adrian.
Title: Re: More problems starting.
Post by: RDfella on 22.11. 2019 14:38
Swarfy - yup, remember those Cord rings. As you say, they were dished, rather like a clutch diaphragm spring, and you fitted them in pairs until the groove was full. They actually worked, too, but that was in old, longstroke, low-compression engines. Dunno if they'd survive in more modern stuff.
Title: Re: More problems starting.
Post by: coater87 on 23.11. 2019 23:38
 I know a guy who siezes rings in the grooves about 1 out of 5 motors, he spins the rings onto the piston,.

 He will never change because thats how great grandpa cobble showed him how to do it wrong a long time ago.

 Maybe this contributed?

 Lee
Title: Re: More problems starting.
Post by: Swarfcut on 24.11. 2019 09:03
RD...My early memories of Cord Rings were with my old fella fitting them to a well worn and smoky Ford E93A "Sit up and beg" Popular van. They changed it from a gross polluter to a real flyer, at very little cost. That was in the 1950's.

 In the 1980s I had a series of Vauxhall Cavaliers, high milers, the rings  successfully cured them all of high oil consumption. Ford Pinto and CVH type motors were transformed as well. Engines with pressed in, rather than floating pins, are a pain changing pistons, so the rings were a quick, cheap and effective cure where the rest of the motor was in good order. The rings were spring loaded, so compensated for worn piston grooves and also sealed well against the bore.

Lee. We all know that because its traditional, it ain't necessarily right.  Applies to a lot of of our behaviour....

Swarfy.
Title: Re: More problems starting.
Post by: AdrianJ on 25.11. 2019 18:47
Just had piston and barrels to the piston supplier.
They reckon it did seize, from the marks on the piston around the crown and the skirt.
When I checked the pistons originally I thought they were stiff and took it to a motor engineer (not the one who fitted the liners) who said it was OK and would run in.
Today measured clearance was 0.0015"
They are boring the barrels out and supplying me with new pistons.
Will let you all know how I get on in a week or so.
Adrian.
Title: Re: More problems starting.
Post by: trevinoz on 25.11. 2019 20:47
No wonder it seized with that clearance.
Title: Re: More problems starting.
Post by: Swarfcut on 26.11. 2019 09:10
BSA published recommended piston/bore clearances for use when genuine parts were the norm as replacements. The clearance depended also on the type of piston, split or plain skirt, and the alloy used in the piston manufacture.

 60+ years later, with various brands of aftermarket pistons available, do Forum Members have any experienced suggestions as to what clearance works the best with what brand of piston?  Just trying to save another barrel, and Adrian's wallet.

Like Trev says, its a wonder it went together, let alone ran. Half a Gnat's Knacker is a dimension, not published, but understood for such a tight bore.

Swarfy.
Title: Re: More problems starting.
Post by: AdrianJ on 26.11. 2019 16:24
Hi Swarfy,
I've left the barrel with the piston people who are boring it out to ( I think) 3 thou all round  (6 total gap).
They are IMD plain skirt pistons.
This leaves the barrel at STD as it has been relined.
Regards,
Adrian.
Title: Re: More problems starting.
Post by: muskrat on 26.11. 2019 18:54
G'day fellas.
Adrian, 3 to 4 thou total clearance is enough not 6. I would use 6 on a race motor.
Modern pistons are made of low expansion alloy requiring a lot less clearance. My rHonda has 1,1/2 thou with standard cast pistons and the same with forged Wiseco's. At 4 thou their ready for the bin.
Cheers
Title: Re: More problems starting.
Post by: Triton Thrasher on 26.11. 2019 20:59
G'day fellas.
Adrian, 3 to 4 thou total clearance is enough not 6. I would use 6 on a race motor.
Modern pistons are made of low expansion alloy requiring a lot less clearance. My rHonda has 1,1/2 thou with standard cast pistons and the same with forged Wiseco's. At 4 thou their ready for the bin.
Cheers

The pistons now commonly available for A10s are not made from low expansion alloy!  Where did you get that idea from?

I don’t see why 6 thou clearance shouldn’t  work.  Works on my other make
of 650z
Title: Re: More problems starting.
Post by: AdrianJ on 26.11. 2019 22:05
It gets worse. The piston chap, has been thinking about it and now doesn't want to bore out the barrel to the required clearance ( 4 or 6 thou). He recommends that I have them bored out to +20 and fit appropriate pistons. He is worried that his boring won't be concentric with the original and is not happy that the barrels have been stove enamelled ( I only had them done on the outside😉) so he's sending them back to me to make my own arrangements.
Tomorrow I will ask my original engineer for his advice, though I suspect that +20 is the way forward.
It will be a while now I suspect before any significant developments
My target of riding the bike this summer has been revised to next spring  *smile*.
Title: Re: More problems starting.
Post by: BSAmoto on 26.11. 2019 22:48
The reason of going to +0.020" is the fear of the machinist that he cannot set-up the barrel on the mill to machine out that small amount of metal that is needed to stay at std diameter and make sure that the bore is machined all the way around - top to bottom.
The solution is to hone only the small amount that is needed and stay on STD diameter. Even if the bore is a little out of round or a barrel or cone shape it can be honed to a true and cylindrical diameter. I have a Sunnen 1804 honing machine and hone barrels very often. So if your barrel is 5/100 of a millimeter too small for your set of pistons, go ahead and hone it. It will be 5 minutes to get those 5/100 out per bore. If you were near me it would be my pleasure to do this for you.

cheers, Harty
Title: Re: More problems starting.
Post by: AdrianJ on 26.11. 2019 23:11
Thanks Harty,
 That's what I wanted to do, but was told that it would take too long to hone out by 4 thou (0.1mm) or so.
 It's a shame that we are not closer to each other.
Adrian.
Title: Re: More problems starting.
Post by: Triton Thrasher on 27.11. 2019 07:03
It does sound like a lot of honing.
Title: Re: More problems starting.
Post by: BSAmoto on 27.11. 2019 07:44
If the barrel needs to be honed out 0,1mm (4 thou) I would use  coarse stones first. This is easy and will not take more than maximal 5 minutes per bore to take out 3 thou. The last thou is then ground out with the finer finish stones.
Title: Re: More problems starting.
Post by: Swarfcut on 27.11. 2019 09:02
Adrian... This is starting to get a bit awkward. The machinist is erring on the side of caution, plus a chance (maybe) to sell another set of pistons. Don't know the finer financial aspects of this, but I would consider a straight no more money swap to be unlikely.

 The original pistons will in all probability clean up well enough for re-use. The rings need to be checked very carefully for correct fitment, end gaps checked and amended if necessary, after the bore has been eased.

 Boring such a fine amount, 2-3 thou from the barrel is difficult, as it's just a 1 to 1.5 thou cut, especially if the boring bar used is a well worn Van Norman portable boring machine. The guy may be well out of his depth with lightweight air cooled engines.

Like Harty says, that amount  should come out with a good hone. May not give the perfection you want, buts gets you up and running in the short term. As to taking too long, setting up to bore takes longer. Sounds as if he is looking for an easy way to scare you away, or contribute again to the takings.

 Moto's on the case here, easy peasey with the right type of fixed stone hone, not the abrasive balls on a wire brush "hone where it touches" type. Those are OK for a polish, not removing material with any accuracy.

Swarfy
Title: Re: More problems starting.
Post by: Triton Thrasher on 27.11. 2019 10:15
If the barrel needs to be honed out 0,1mm (4 thou) I would use  coarse stones first. This is easy and will not take more than maximal 5 minutes per bore to take out 3 thou. The last thou is then ground out with the finer finish stones.

How much finer?

Something fairly rough like 130-180 grit helps seat the rings.
Title: Re: More problems starting.
Post by: RDfella on 27.11. 2019 12:01
Agree with Swarfy, BSA etc - the machinist is right - I wouldn't risk trying to machine such a small amount. Always a risk it won't stay centre of bore and then it's oval and oversize.
Honing is the answer. Indeed, you normally bore undersize and then hone to size. Need coarse stones first as S & B suggest, finishing the last 1 to 1 1/2 thou with fine. Total about half an hour. Sounds like the machinist knows what he's doing but is unfamiliar with engine cylinders.
Title: Re: More problems starting.
Post by: BSAmoto on 27.11. 2019 15:11
Start with a 100 or 150 corn and finish the last 1/2thou with a 400. This gives a very long lasting barrel as the spikes of surface are platoed by the 400 thus the oil holding channels are still there but the surface gets more area of contact.
Title: Re: More problems starting.
Post by: AdrianJ on 10.04. 2020 13:07
Finally bike is running and together. Thanks all of you for all your help.
Pictures posted in Stories etc.
Adrian