1962 A10 Flash, Starts, but won't Pickup

[jhg1958]

Many years ago when I was a young man. I bought an old A10. It did not have a spark so was told that damp in the mag causing problems.  I was told that The cure was to bake the mag in the oven. I did this and hey presto it worked.

Not sure if this is your problem or the cure but it may be worth thinking about.

John

[Adler]

Hello TerryB,
I am a newbie in BSA A10s, but I actually had the same problem on my Zündapp K500 (a boxer twin). In the beginning I sorted out the carb problems (main jet, needle height, petrol height controlled by the float needle, etc.), next was the manual (battery) ignition timing. I found, my Zündapp being veeeery sensitive for a "wrong" position of the ignition lever at the handlebar - do not laugh, but this in the end was solving the problem. The machine runs perfectly since then.
With my A10 I had a similar problem. Starting OK, idling as well, revving not so well ... same procedure, carb check, some adjustments in the beginning right according to haynes manual and other sources. Then the magneto ... I admit obviously being not sensitive enough to achieve the right spot on timing for somehow 34 degrees BTDC, so I eventually found the very good solution being presented by Mr. Orabanda here:
https://www.a7a10.net/forum/index.php?topic=947.msg6520#msg6520
I do not have a milling machine but elongated the three holes to slots by manual filing and was very satisfied with the result. Having the magneto somehow timed as good as possible at first place, I started the machine and tried to fine adjust the timing by rotating the magneto and it works fine for me since then (thanks to Orabanda (Richard)).
Maybe, TerryB, you can try this for yourself. If a machine was running once, why should it not run again. Good luck.
Best regards, Manfred

[CheeserBeezer]

I really don't think it's a timing issue, more likely a fundamental or simple issue with the mag itself.

[BagONails]

Me too. Assuming you know valve timing is correct, compression is OK and you've done a proper leak down check?

Its starting to sound like weak spark breaking down under compression and/or ignition timing 'scatter' which all points to magneto.

Have you been able to run it well enough to check timing with a light?

[Terryb]

OK Guy's firstly I want to thank you ALL for your input into solving my problem. This is a great Forum

Over the last few days I checked that I had a regular spark on both cylinders, checked valve clearances, Timing and eventually the New Carb, which was purchased by my mate for a 1961 Super Rocket. On closer inspection and checking the AMAL book, firstly it had the wrong size Pilot Jet, a 25 instead of a 30 and secondly the wrong Throttle Valve, a 3 instead of a 3 1/2. With the correct Carb setup and a temporary fuel line she starts, picks up and ticks over nicely

It just shows it pays check and double check and consult the manufacturers specifications.

[sean]

When I bought a new amal for mine the dealer asked me if I wanted it jetted to factory specifications.
British Cycle supply

[Terryb]

Yes you’re right Sean, it was for the SR when purchased. Then I bought it second hand 🤪

[CheeserBeezer]

OK Guy's firstly I want to thank you ALL for your input into solving my problem. This is a great Forum

Over the last few days I checked that I had a regular spark on both cylinders, checked valve clearances, Timing and eventually the New Carb, which was purchased by my mate for a 1961 Super Rocket. On closer inspection and checking the AMAL book, firstly it had the wrong size Pilot Jet, a 25 instead of a 30 and secondly the wrong Throttle Valve, a 3 instead of a 3 1/2. With the correct Carb setup and a temporary fuel line she starts, picks up and ticks over nicely

It just shows it pays check and double check and consult the manufacturers specifications.

I'm delighted for you. However (sorry!) I don't see how the carb settings would cause the problem you had. The consequences of the incorrect jet and throttle valve would be slightly rich running and probably not noticeable from cold. Are you sure the solution isn't the temporary fuel line?

[Terryb]

CB I’ve just fitted the tank and she runs ok. I was surprised, I’ve just had it running for 20 mins to warm up the oil to change it. So once that’s done I’ll push her into the garage, when the rain stops and finish setting the carb up and fingers crossed take her up the road. I have checked both tank taps and they seem fine.

[Terryb]

CB just sussed out what was causing it not to pickup, the carbon brush in the end of the Mag Cap is missing and only the spring is connecting. So I think that when it started the vibration caused the spring to disconnect and hence cut the juice 🥴 so when I removed the cap to check the timing and then refitted it, the spring has made a better connection so it ran ok and the cutoff button worked. Thinking about what you said i decided to do some more checking, tried to start the bike again and nothing, checked and no spark  removed the Mag end cap to check points and out jumped the spring. After hunting around for an hour or so couldn’t find the brush only the spring. Tomorrow I’ll check the garage floor to see if I can find it, if not I have others

At leased I now have the correct Carb setup 

[Adler]

Hello TerryB,
I hope you are on the right way, but: have you already checked the ATD unit just in case of having everything (!) checked. Two members in this thread mentioned it already. If the potential carb problems have been sorted, I really would suggest checking the ATD working properly.
Best regards, Manfred

[CheeserBeezer]

CB just sussed out what was causing it not to pickup, the carbon brush in the end of the Mag Cap is missing and only the spring is connecting. So I think that when it started the vibration caused the spring to disconnect and hence cut the juice 🥴 so when I removed the cap to check the timing and then refitted it, the spring has made a better connection so it ran ok and the cutoff button worked. Thinking about what you said i decided to do some more checking, tried to start the bike again and nothing, checked and no spark  removed the Mag end cap to check points and out jumped the spring. After hunting around for an hour or so couldn’t find the brush only the spring. Tomorrow I’ll check the garage floor to see if I can find it, if not I have others

At leased I now have the correct Carb setup 

The brush and spring in the end of the mag make contact with the points centre screw, so when you press the kill button the points earth out. The bike will run fine with no brush and spring, but you won't be able to stop it!

[Terryb]

Yes, but is it possible for a displaced spring to cause it to earth out? I’ve checked the ATD, that seems to be working ok. Im  beginning to run out of areas to address and this thread is running into a paperback 

[Terryb]

Well Guys, just close out this thread, I’ve just come back from a 10 mile test ride which went well. Since my last post I’ve changed the plugs to extended tipped NGK BP7HS plugs to try and solve difficult cold starting. Some improvement but I’m working on it, otherwise when warm she starts first kick. Only one oil leak on the speedo cable to sort and fit mirrors.

[Bsareg]

Still difficulty starting, are the plug caps non resistive ?