Author Topic: 59 A7 starting problems  (Read 3993 times)

Offline Gasket4450

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59 A7 starting problems
« on: 08.12. 2013 13:24 »
Hi Musky.
                 We have communicated before on this Forum under my post ' Refuses to Run ', which was traced to a dodgy magneto. All now fixed, thanks to Ken Targett at Brightspark . However, although the mag now sparks better than I've ever seen, my A7 engine is still very erratic, and won't run properly on both cylinders. It still sounds as though the timing is way out. Then I had a sudden flash of inspiration  *idea* -  I remembered that when I put the engine together some while ago, the only camshaft I had to hand was a brand new 357 !!!  I remember thinking to myself at the time: " Must remember - different valve timing ". What I have, therefore, is everything set up for a 356 cam. When I happened across your figures in the above post, I realised that I had seen those figures somewhere before, at the back of Roy Bacon's book, the 'Bible'. Am I right in thinking that a 357 cam with valves set at degree timings for a 356 would cause the worst possible running imaginable ???
                  I suspect this may have been part of the starting problem from my original post in the first place ( ...although, of course, I now have a nicely refurbished magneto, so some good's come out of it ). I have a degree disc mounted on the crank with plasticine, and I presume I now need to adjust the valve timing by some judicial adjusting of the tappets - would that be correct ?
                 Can't believe I've been such a bonehead. Doh !! *doh*  

Norman T
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Online chaterlea25

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Re: 59 A7 problems
« Reply #1 on: 08.12. 2013 16:42 »
HI Norman,
I'm not 100% sure I can follow your logic??
Regardless of which cam is fitted, just make sure the pinion timing marks are lined up when assembling the engine
The pinions are not different for 356 and 357 cams
(Beware if building an engine from parts as I believe longstroke pinions are marked differently)  *????*
As stated because of the intermediate idler/ dynamo driving gear size the marks only line up every so often
(in engineering terms this is called a hunting tooth arrangement)

To check the valve timing in degrees theres a wider clearance specified, so as to avoid the opening and closing ramps
As the cams and followers wear these figures alter somewhat, so its difficult to be accurate
Thats where checking the "lobe centre " method comes into play,
Theres no need to bother with this unless racing the engine

I just noticed that my last post has been edited *ex* *ex* *ex*
The engine I was talking about was a 1920's J.A.Prestwich  (J.A.P) and not some product from Japan  *eek*

Regards
John

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Offline Briz

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Re: 59 A7 problems
« Reply #2 on: 08.12. 2013 17:33 »
Norman, theres no way of adjusting valve timing on an A10 without some custom engineering work such as a vernier pinion.
I believe you're talking about tappet clearances. Altering this makes small differences to valve timing & lift, but nothing thats going to affect running more than the adverse effect of wrong gaps.
A 357 works fine set at .008 intake and .010 exhaust.

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Re: 59 A7 problems
« Reply #3 on: 08.12. 2013 18:46 »
G'day Norman.
Please take note of both John & Briz's replies.
The two main culprits for uneven running are carb (bias) and timing.
Is yours a manual or auto advance? Have you checked your timing with a degree disc and strobe light. I recently checked a mates A7, he set it up with a fag paper and said it was spot on. I checked with the disc & strobe, timing at full advance was 55 deg instead of 35 deg.
You will need to attach the disc with a bit more than plasticine *eek*. Between the cush nut and spring.
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Offline Triton Thrasher

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Re: 59 A7 problems
« Reply #4 on: 08.12. 2013 21:38 »
I recently checked a mates A7, he set it up with a fag paper and said it was spot on. I checked with the disc & strobe, timing at full advance was 55 deg instead of 35 deg.


My magneto timing took a big leap forward from the static setting, at higher revs, when the points pivot and the pivot hole were worn.
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Offline Gasket4450

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Re: 59 A7 problems
« Reply #5 on: 09.12. 2013 00:41 »
                My thanks to all for your advice. I think maybe I got the wrong end of the stick with the different figures quoted in Roy Bacon's book, and by yourself Muskrat. My engine is a standard 1959 iron head A7, with auto advance and retard. Everything that was worn I have replaced. I have timed it at 5/16" BTDC on the right hand cylinder, with points gap set to .012, and .002 when just about to open at 5/16 BTDC. Auto advance bolted up in fully advanced position ( the famous wooden-clothes-peg-in-the-arms dodge ) ( and yes, before you ask, I did take the wedges out before putting the timing cover back on !!! , although I do know of someone who didn't ).
                 I set the valve clearances according to the Haynes manual at 10 inlet and 16 exhaust, set when cold ( .....it's always cold 'cos it doesn't run . ha ha. ), although I will try 008 and 010 Briz, thanks.
                 The carb is a 376 monobloc, with 210 main, 25 pilot, and 106 needle jet, with new float needle kit, including one of those Viton tipped needles.              

                When I tried to fire it up, the left hand cylinder ran very sluggishly, the right didn't fire at all, just blew out some white smoke occasionally. Opening and closing the throttle made no difference to the engine speed whatsoever. It ran for about a minute, and then died. Same thing happened on each occasion, with the occasional cough from the right hand cylinder. When the engine died, the left hand exhaust was red hot, the right hand was tepid, so something must have been happening on the right. It sounded as though it had to be timing. That's why when I read the difference in degrees of rotation of the crank for the different camshafts I thought I had solved it. I was forgetting that since the cams have different profiles, valves will naturally be fully open and closed at different degrees of rotation of the crank. I have not tried it with a strobe because it will not run long enough to check it.
              
                 My thanks to John and Briz for your wise words. Unfortunately, it looks as though I will have to trailer it in to my local Brit bike garage, Roadstar Cycles at Dover, who are most helpful, and who know a thing or two about old Brit iron.
              
                 I don't like to admit defeat, especially when my last project, my 1960 A10, went from scratch without too many problems.
Thank goodness I still have one bike that works !!!  I will keep at it, however, and report back in due course.
 
Thanks once again
Norman
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Offline duTch

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Re: 59 A7 problems
« Reply #6 on: 09.12. 2013 11:22 »
 Hey Norm,
 I did read it all,I have a A10 Plunger with 357 , S/R big valves, 7.25's, 389 experimenting with 25/30 idle, 250 main, 105 needle jet(which made a massive difference), and for now, it's running fine without even a (serious)thought of the valve timing but can't recall if you said you tried a different set of plugs....?

 If not might be worth a go, even new ones can be dodgy...?
 Also had to screw the idle mix a fair bit with jet changes (check for blockages too,which I had)
 
   Just my thoughts, good luck, duTch
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Re: 59 A7 problems
« Reply #7 on: 09.12. 2013 11:57 »
Have you done a compression test, done with the throttle wide open? Have you swapped the leads, caps and plugs? What do the plugs look like?
It will end up being something really silly causing it. *conf*
Cheers
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Offline Gasket4450

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Re: 59 A7 problems
« Reply #8 on: 09.12. 2013 20:07 »
            Thanks for your views duTch.  Sorry it went on a bit, but I was trying to give as full a picture as possible. I will try a different combination of main and needle jets, and see how we get on. Yes, I have tried swapping plug leads and caps. I use B6HS, and have also found they can be crap straight out of the box, so have half a dozen or so I can play with.
         Musky, yes you are right, it will be something silly, which is why I am annoyed I can't find it. Plugs look OK, the left side is a dry dark grey colour, which would be right, I guess. The right hand plug appears spotless and brand new, and although it smells of petrol, it is bone dry. Have not tried a compression test as can't lay my hands on my old gauge at the moment ( although fingers in the plug holes work reasonably well....) ( ...somebody else's fingers, that is.....! ).
         Do I remember reading somewhere in this splendid Forum that brand new Amal carbs have been known to contain swarf ?
Just a thought, as the one I have is straight out of the box. I do have a couple of old ones I can experiment with, so that should keep me out of mischief over the winter. Will get out the ultrasonic cleaner again, although I usually poke out the holes with a piece of lightweight fishing line where I can.
         Thanks again. I will not give up, even if I have to rebuild the damned thing all over again !!!

Norman T
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Offline shabashow

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Re: 59 A7 problems
« Reply #9 on: 12.12. 2013 19:50 »
90% of all carburation faults are due to the magneto, and most magneto faults are due to the carburettor ;)

The problem will be something so simple, you'll be laughing about it afterwords, as I know from recent experience. I spent half a day tracing problems with my bike (A10 plunger) after a recent rebuild. It would start fine, but as soon as I took it for a spin, it wouldn't accelerate, ran intermittently on one pot, and was a right pig. After about 5 hours of trying everything I could think of, I noticed that the air slide (choke) was down. As soon as I put the air lever back in its correct position, the bike started and ran perfectly.

A clean plug smelling of petrol - could it be flooding on that side?  
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Offline Gasket4450

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Re: 59 A7 problems
« Reply #10 on: 13.12. 2013 19:22 »
Hi shabashow, thanks for joining this saga.....!!

                    Yes, I tried altering the position of the air lever at all points of the operation, but without success, I'm afraid. When the choke slide was closed the engine died altogether. Since opening and closing the throttle didn't make a blind bit of difference, I wonder if maybe the needle is set too low, and is not clearing the needle jet sufficiently (....is it even the right needle, I wonder ? ).  The Amal service sheets suggest a ' C ' needle for the 376, and a  ' D ' for the 389, and either position 2 or 3........ does anybody have any alternative ideas please, just in case ?

                    I suppose the only good thing about this is that winter is upon us, and at least I won't be wasting time in the workshop when I could be out riding with my mates  *smile*.

All the best
Norman

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Offline duTch

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Re: 59 A7 problems
« Reply #11 on: 13.12. 2013 22:00 »
 Hiya Norm,
                 If, after switching plugs, leads, caps and cleaning pickups, brushes and slipring or trying different pickups-, doesn't change any, did you try re-timing it 180˚ around... ( L<->R )....?

(I think you can swap pickups over, 'cos I had two the same for a while- don't fit the same but for a test, be ok?)
      If the situation reverses, it suggests maggie related, if not- suggsests valves or mechanical....?
  
Did you say if the points are opening the same both sides...?
  Hard to understand how it can be fuel/carby related with a single carb...?
 cheers, duTch
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Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
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Offline raindodger

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Re: 59 A7 problems
« Reply #12 on: 14.12. 2013 13:49 »
Hello.
        Red hot pipes are a sure sign of very retarded ignition.
raindodger
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Offline shabashow

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Re: 59 A7 problems
« Reply #13 on: 14.12. 2013 14:09 »
I would concur with the retarded ignition timing prognosis. Last time I timed my bike, the magneto pinion must have slipped or moved (that's my excuse, and I'm sticking to it) when I put the timing cover on. It was also misfiring and not responsive to the throttle. It could be something as simple as that, as our engines aren't too complicated, and if your getting fuel and sparks, the next logical step it to ensure the sparks happen at the right time. Could you have timed the engine after tdc instead of before tdc?

You must be close to a solution, as there's only a few variables that can alter.
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Offline duTch

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Re: 59 A7 problems
« Reply #14 on: 14.12. 2013 14:50 »

Quote
did you try re-timing it 180˚

 I just had a sudden dyslexic thought that my previous idea may be the same as switching leads, but that would need to be done also anyway
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Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
Australia