The BSA A7-A10 Forum

Technical => Lucas, Electrical, Ignition => Topic started by: Tumbleweed on 15.05. 2013 15:30

Title: engine wont run
Post by: Tumbleweed on 15.05. 2013 15:30
hello everybody, i dont know wether you can help on this one, after a top end overall , rebore, new pistons/ rings ,valve grind ,clean carb, timing spot on new plugs,caps , leads,mag  pick ups,clean slip ring , ive been trying to get the ******* thing going for days now , all of a sudden (after a lot of kicking over) it will fire up and run rough for about 15 secs and then stop, and wont start again at all  i take out the plugs check the spark , clean the slip ring reset the points gap , and try again for ages the same thing all the time , i did have it running for about 30 secs once but i could not take my hand off the throttle to grab a screwdriver,        i think my leg is about to fall off *problem*  p/s i have searched the posts but cant get any info
Title: Re: engine wont run
Post by: TT John on 15.05. 2013 15:38
Hi There

What bike is this we are talking about?  Have you checked valve timing?

TTJohn
Title: Re: engine wont run
Post by: bsa-bill on 15.05. 2013 16:00
Quote
timing spot on new plugs
Quote
take out the plugs check the spark

Can be a torturous path working through what could be wrong. DAMHIK
These bikes should start after three kicks often less, if it doesn't your time is better spent working back through the things you've replaced, new stuff does fail unfortunately
Could do with a bit more info though - model and so forth
Some suggestions - no offense intended if you've already been through them  

timing can be spot on but on the wrong spot however if it has fired up and run for a short while the timing cannot be far out, unless it's moving - check magneto pinion AA unit points plate and cam ring are fixed.

all being well there, change back to your old plugs, a spark with the plug sitting on the crankcase does not necessarily mean there will be a spark in the combustion chamber and new plugs are notorious for giving up the ghost in the dark  or damp.

 the carb, are the plugs wet after kicking over, valve timing (easy to move the engine with the idler off again DAMHIK)

My stab in the dark would be plugs followed by carb - anyway best of luck with it and remember rest your leg after three kicks and exercise eyes and little grey cells

Title: Re: engine wont run
Post by: Tumbleweed on 15.05. 2013 16:19
thanks, i will look at those things , there must be something i am doing wrong,  BSA A10 1954 , and the plugs are dry  mainly , sometimes damp.  cheers      TW
Title: Re: engine wont run
Post by: a101960 on 15.05. 2013 16:26
Given what you said, that the engine has run but only for short bursts, and that you have cleaned up the carburettor my inclination would be to make sure the pilot screw is set in the right position. Turn the screw in until it is fully closed, and then turn it back out one and a half turns.

John
Title: Re: engine wont run
Post by: mayes on 15.05. 2013 17:11
Hi back to basics check fuel carb is a good start check needle setting start on 3rd check pilot jet ensure carb is clean and clear
Title: Re: engine wont run
Post by: Tumbleweed on 15.05. 2013 19:11
thanks,   i will start again  in the morning , i  never had old plugs with the bike, i dont know if both new plugs would pack up at the same time *sad2*      bill whats DAMHIK ?
Title: Re: engine wont run
Post by: bsa-bill on 15.05. 2013 20:50
Quote
, i dont know if both new plugs would pack up at the same time

If they both get wet at the same time they'll pack up at the same time, it has been known.
But carb seem the first suspect
Title: Re: engine wont run
Post by: muskrat on 15.05. 2013 20:57
DAMHIK = don't ask me how I know = Doh I made that mistake.
Sounds like she's not getting enough fuel. Tank taps or filters blocked. Fuel hose restricted/melting from ethanol fuel. Needle and seat blocked. Float sticking up.
Cheers
Title: Re: engine wont run
Post by: morris on 15.05. 2013 22:25
Noticed you put on new caps. They are not by chance suppressor type? I made that mistake, and after going back to regular caps, the spark was noticeably fatter. A DAMHIK would not be out of place here.
How did it run before the overhaul?
My A10 was getting more and more starting and rough running problems, and in spite of cleaning the carb twice, and changing all the carbs gaskets, it kept on getting worse.
As it was worn, and not the correct type anyway, I bit the bullet, and ordered a new one. At first I had to fiddle a bit with different pilot jets and needle settings, but since getting that right, it never ran any sweeter as it is now.
Just remember; there's a solution to everything wink2
Title: Re: engine wont run
Post by: orabanda on 15.05. 2013 23:50
I would try changing both plugs, having also fouled two new plugs at start-up before.

Richard
Title: Re: engine wont run
Post by: wilko on 16.05. 2013 00:40
What carb. Blocked pilot jet.
Title: Re: engine wont run
Post by: Topdad on 16.05. 2013 13:18
I'd noticed the caps mentioned like Morris so that may need looking at however if all the associated info given above doesnt work it will be back to basics. whizz the tappet covers off  and whilst checking Ing timing make sure the valves are closed . If that checks out can you borrow a spare carb ?, by then you'll have checked fuel flow from tank as per Muskys thoughts and another carb would at least take the carb out of the equation. A bit drastic but if you can't borrow a spare  how about a squessy bottle of fuel and squirt some direct through the carb only have an extinguisher handy just incase. As already said there is a solution ,  it can only be a) mechanical :- valve timing ,lack of comp.
                                    B) electrical :- mag leads plugs
                                    c) fuel   :- carb fuel taps
                                    d) restricted exhaust.
 just thought of another problem I saw once ;the bolt holding the points to the mag also hows the keyway and just by chance the bolts not dirty at the contacpoint or have a fibre washer fitted to it .I once saw a bike kicked for ever which a kind sole had fitted a fibre washer on that bolt and isolated the points from the mag ,may be completely wrong but have a look   
Title: Re: engine wont run
Post by: A10 JWO on 16.05. 2013 17:51
Does sound like those drilled out pilot jets are blocked, see the thread I started on this, loads of good input from the lads.

Regards Colin
Title: Re: engine wont run
Post by: Tumbleweed on 17.05. 2013 08:49
just put a new pilot jet in the other day colin , i am going to get some more plugs to day and start again from the beginning as suggested, the springs on the aa unit dont seem very strong to me i suppose that could be another prob , i dont know anything about the engines history, just getting it running long enough to listen to it would be a bonus  ,   cheers and thanks everybody for your help as well
Title: Re: engine wont run
Post by: Tumbleweed on 17.05. 2013 14:37
hello all, i removed new plug caps and wired direct to plug, removed brand new champion L82c plugs and replaced with nkg b6hs (thanks colin/ richard   )  , cleaned the mag slip ring , and kicked it twice and it was away for about 5 mins even got it almost to tick over , then my petrol feed bottle ran out of fuel so it stopped i topped it up   now it wont start again . as you say there is a solution somewhere , and im getting there, so it  dont bother me so much, thought i would mention the plugs for the record.     thanks, any more info will be welcome,        :!   TW
Title: Re: engine wont run
Post by: A10Boy on 17.05. 2013 14:56
I have a sneaking suspicion of your condenser. When was the mag last overhauled, do you know? If it starts and almost ticks over and only stopped cos it ran out of fuel there can be much wrong with the rest of it.

Dont worry about the springs on the AR unit, they always seem weak but the rotational forces versus friction of turning the mag always seems to close them.
Title: Re: engine wont run
Post by: Tumbleweed on 17.05. 2013 16:17
i dont know anything about the mag it looks in good nick to me not like some ive seen , i know you cant tell just looking ive noticed there are no shims in the casing , it sparks across a 60 th gap on a plug but  not very strong ,i dont know how it should be , but it sparked ok off the bike run with a drill.   
Title: Re: engine wont run
Post by: A10Boy on 17.05. 2013 16:22
Unfortunately, that don't mean a lot..
Title: Re: engine wont run
Post by: Tumbleweed on 20.05. 2013 11:01
hello again, the engine started again first thing this morning, it ran for quite a while tuned it to very near tick over, then stopped it , now it will not start i have a spark at the plugs and the slip ring is cleaned so it could probably the mag as has been suggested, i think it will have to come off again, glad to hear the aa springs are probably normal  , i am nearer today than i was last week so thats got to be good *smiley4*
Title: Re: engine wont run
Post by: KenF on 20.05. 2013 19:38
i dont know anything about the mag it looks in good nick to me not like some ive seen , i know you cant tell just looking ive noticed there are no shims in the casing , it sparks across a 60 th gap on a plug but  not very strong ,i dont know how it should be , but it sparked ok off the bike run with a drill.   
The Lucas slow running spec was that it should give an almost consistent spark (not more than 5% missing) across a 5.5 mm (220 thou) 3-point test gap at 130 mag rpm if it's fixed timing (or ATD), or if manual timing at 110 mag rpm advanced, and 150 mag rpm retarded.

A rough equivalent to a 5.5 mm 3-point test gap is an old plug with its earth electrode cut/ground off so that the spark has to jump the approx 4mm gap between the centre electrode and the plug body. If your mag will spark that reliably when cold and hot with a leisurely prod of the kickstart, or off the bike powered by a drill/lathe so that it's producing 4 sparks per second (a reasonably fast count of 1, 2, 3, 4, 1, 2, 3, 4 ...), your mag's probably OK. If not, it needs looking at. Could be condenser, broken HT winding, or breakdown of insulation of the windings, slip ring or pick-ups.

Best of luck,

Ken
www.brightsparkmagnetos.com (http://www.brightsparkmagnetos.com)
Title: Re: engine wont run
Post by: Tumbleweed on 22.05. 2013 11:17
 *eek* thanks ken
Title: Re: engine wont run
Post by: RichardL on 22.05. 2013 12:52
Ken,

Might/could/should demagnetization be on your list. When I intalled my EasyCap I also remagnetized. I know, not great scientific analysis practice, changing two variables, but the goal was a working mag and I definately ended up with that.  

TW,

To find a place nearby me with a magnetizer that would work, I seached for a magnet supplier, gave them a call, described the bike and they invited me over. Gent spent a good amount time helping me, no charge, just a promise to drop by on the bike so he could see it.

Richard L.
Title: Re: engine wont run
Post by: KenF on 23.05. 2013 08:13
Sure, Richard, a weak magnet can exacerbate all sorts of other problems with a mag. But that list of things to do is aimed at what people can check while the magneto is still on the machine and without specialised equipment.

All the best,

Ken.