Author Topic: Ignition question  (Read 1002 times)

Offline Andreas Larsen

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Ignition question
« on: 04.04. 2016 12:30 »
Hello everyone,

I've been trying to get the ignition timing right for my A10, but it seems I simply can't get it right, and I'm a little bit in doubt if I'm doing something wrong. So in hopes of getting a tip or finding an error in the process I'll tell what I've been doing so far. I haven't been able to get it to fire and I would really like to take it out for a spin soon so I hope that someone could tell me if I'm doing something wrong. Thanks :)


First, removing the timing cover, and taking out the magneto pinion (it's an auto advance one).

Then finding the compression stroke on the timing side cylinder by placing a finger over the plug hole and rotating the engine till I feel compression.

Rotate the engine forward slowly by means of the back wheel in 4th gear til the piston is at the top of the stroke (I've been using a straw for this part)

At the top of the stroke I've then measured the position of the piston using a caliper (at the bottom of the caliper there's that small metal thingie that will shoot out, I'm sure you know what I mean)

Right, my Danish manual tells me that the ignition full advanced should be 8,7mm BTDC or 11/32in

right, then turning the engine back again, just past the 8,7mm drop (measured from the original piston drop position using the calipers) I rotate the engine back forward til I can just feel the piston hitting the caliper.  At this point the engine should be at the correct position if I'm not doing anything wrong obviously.

Then I wedge the ATD unit and replace it on the magneto shaft loosely and then rotating the magneto clockwise til it just releases a piece of cigarette paper.

Tap the mag pinion gently back and hand-tighten it (remember the c-clip thing), again I measure the engine position and check that the mag has not rotated. Then as best as possible I've held on to the mag and then tightened the pinion bolt.

After all this I've rechecked the positions and they seem to be correct.


This is the method I've been using..
As a bonus info I can tell that the breakers open roughly 4degrees apart (measured on the crank), so that at the primary side the breaker will open slightly closer to TDC.
Also, as a side question, if I were to use a timing disc in stead of the caliper for measuring piston drop, would it be the oil pump shaft it should be attached to on the timing side?

I hope that anyone can point me in the right direction, or confirm that this is correct and the fault is somewhere else.


All the best
Andreas
'58 A10 swingarm

Offline Topdad

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Re: Ignition question
« Reply #1 on: 04.04. 2016 14:10 »
Good afternoon Andreas, mostly ok but what point gap are you using ,that's the one thing you don't mention.
I'd have the points out ,check for pitting ,clean and adjust to 12 thou. ciggy paper between points and rotate mag  until just releasing. I use 5/16 BTDC with the valve gear rocking( whichever side ),I've not had to whack the pinion first but with it wedged fully advanced , just tighten on then, recheck ciggy paper if all ok you're done.
If you want a timing disk I think the norm is to use of the drive side cushdrive. I've never used one but may next time I do this job. cheers ,in fact I think Musky has a very neat one fitted perm to his bike, hope that's of help, regards bob
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Offline Andreas Larsen

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Re: Ignition question
« Reply #2 on: 04.04. 2016 14:44 »
I think it was 11 thou, the point gap, last I checked. But on that note, how do you measure that accurately? since the arm can be move ever so slightly finding out exactly what the gap is seems a little hard to me?

Cheers
'58 A10 swingarm

Offline Topdad

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Re: Ignition question
« Reply #3 on: 04.04. 2016 14:55 »
the points can be removed by completely undoing the small centre nut and gently pulling out the out the points assembly .Once out you'll see that the gap is adjustable by moving the small nuts ,I'd take it all apart and clean the points to remove any pitting , in days of old you'd be able to get magneto spanners ,to adjust these nuts which are obviously small to enable adjustment .  Maybe grind down a suitable spanner to fit ?? or contact our Mag and Dynamo guys who also are dealers ,priory magnetos or Groily . cheers Bob
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Online Greybeard

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Re: Ignition question
« Reply #4 on: 04.04. 2016 16:56 »
Possible dumb suggestions but are you sure that the plugs are not firing on the opposite cycle? Try swapping the HT leads if they are long enough.
Does the plughole smell of petrol? (fuel)
Do you have compression? (mechanicals)
Lay a plug on the cylinder head, turn the machine over; is the plug showing a nice fat blue spark? (Ignition)

Is the engine sucking in a petrol/air mixture? Does the engine have compression when a piston is at TDC? Is there a healthy spark, (Note: a faulty plug can break down under pressure)? Is the spark occurring at the right time? Is the exhaust clear? In my experience if all of these conditions are met the engine must, (should) run.

Offline bsa-bill

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Re: Ignition question
« Reply #5 on: 04.04. 2016 18:05 »
timing disc on the timingside? I use the cushdrive, should make no difference provided you've got the engine rotation sussed
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Offline Andreas Larsen

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Re: Ignition question
« Reply #6 on: 04.04. 2016 18:59 »
Graybeard thanks for the suggestions! My HT leads sadly aren't long enough to swap around, there is spark when I turn it over, one is nice and fat the other perhaps a bit less so - I'll order a couple new ones just in case.. I have compression I know - I had it tested by a friend but I can't recall the numbers. No petrol smell though as far as I can tell. I could order up a couple new HT leads that can reach both sides?

Also, I decided to clean up the points, one of them had gone pretty concave... but sure enough on my way back to the bike I dropped it and the brush broke.. So I guess I won't know if it helped anything for a few days.

Edit: The reason I didn't put the disc on the cushdrive is that I've run out of oil to refill it if I pull the primary cover, so I was just curious if it could be done on the timing side as well
'58 A10 swingarm

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Re: Ignition question
« Reply #7 on: 04.04. 2016 19:13 »
...My HT leads sadly aren't long enough to swap around...
You might try swapping at the mag end.
Quote
No petrol smell though as far as I can tell.
I would have thought that if you've been kicking the bike over for a while you should see wet spark plugs. You might try pouring a little petrol into the plug hole to see if the engine fires momentarily. There is that volatile stuff, (ether?) that you can spray into a carburetor to get a sluggish engine to fire. I've never used it. I think it may be a bit cruel to treat an elderly engine so roughly.

Offline chaterlea25

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Re: Ignition question
« Reply #8 on: 04.04. 2016 23:16 »
Hi Andreas,
Quote
Then I wedge the ATD unit and replace it on the magneto shaft loosely and then rotating the magneto clockwise til it just releases a piece of cigarette paper.

Which end of the magneto are you referring to?
Looking at the timing cover side the magneto rotates anticlockwise
the points end rotates clockwise

Was the A10 running previously?

Heres a link to the timing instructions

http://www.bsa-oc.com/wp-content/uploads/bsk-pdf-manager/74_SECTIONY_BSASERVICESHEETNO801.PDF

John

1961 Super Rocket
1963 RGS (ongoing)

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Re: Ignition question
« Reply #9 on: 05.04. 2016 07:54 »
Sorry to point out the obvious but it is possible to shift the timing around 180 degrees during the timing procedure isn't it? In which case having leads that are too short to swap will not prevent you having them the wrong way around as per the suggestion in the previous post.

If it is not firing at all, but you have a spark and wet plugs, it does indicate the leads are the wrong way around......or your engine needs a different starting technique (most seem to like a flooded carb and quarter or more throttle).

You can check the mag is firing on a compression stroke by putting your finger over the plug hole and feeling for compression and tdc, and then checking the mag slip ring is showing brass under the correct brush/plug lead.



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Offline roadrocket

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Re: Ignition question
« Reply #10 on: 05.04. 2016 08:12 »
It sounds like you have the procedure right, but maybe some more accurate tools would show a difference? I use a screw-in tdc-finder readily available from many dealers, with a metal rod running in a bore without slop. I have marked the advance on this, taking the angle of the spark plug hole into consideration. I t beats taking the cylinder head off :) Also I use an electronic points indicator, which in my experience is lots more accurate than a piece of cigarette paper. This has not prevented me from timing the wrong cylinder though, but my mistakes have always shown themselves after a plug lead swop.
Otto in Denmark

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Re: Ignition question
« Reply #11 on: 05.04. 2016 08:18 »
Just for interest here is how BSA suggested to do it.

Online orabanda

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Re: Ignition question
« Reply #12 on: 05.04. 2016 08:53 »
Good one Brian; no-one spoke about that bulletin before!

(sorry!)

Offline Topdad

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Re: Ignition question
« Reply #13 on: 05.04. 2016 11:14 »
I've never seen that before ,very simple and works !!. I'm very lucky that I've never had a problem setting the ignition timing ,basically being a simple sole I keep it simple .  With this little idea I'll continue to use my HB pencil to set the BTDC , oh I've just been modernised  *conf2* ..erm by an old idea ??
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Offline Andreas Larsen

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Re: Ignition question
« Reply #14 on: 07.04. 2016 18:47 »
Thanks for all the help everyone.

It was running previously, but the it had some running problems due both to the springs on the auto advance unit was in need of a replace, and also that the petrol tank was fitted with some cheap aftermarket petrol taps where the rubber inside would swell after being open a few minutes, I'm guessing due to ethanol? Anyways, ever since replacing the springs on the ATD my timing got messed up because I was not careful in the process.. the engine was in fact renovated 1700miles ago, so it's only my own ineptitude that has resulted in the non-running condition I would think :)

Once I get a stack of brushes to replace the one I broke I'll give it another few kicks and see what happens.. I've only had it for a couple of years so I just don't know it that well yet.
'58 A10 swingarm