The BSA A7-A10 Forum

Technical => Lucas, Electrical, Ignition => Topic started by: Bill18 on 12.03. 2011 01:54

Title: Ignition timing troubles A10
Post by: Bill18 on 12.03. 2011 01:54
I have nearly completed a rebuild of an A10 (a 32 year project believe it or not) and am up to the ignition timing part. The magneto has automatic advance. The head is on but I am pretty confident of getting the piston position right. I have good spark when kicking over the engine but when I loosen the spindle and turn the points to get the them just opening at 3/8ths befor TDC; and then tighten the spindle again - alas no spark. It is as though I have lost the connection with the magneto coil. I had the magneto rebuilt but the brass base that carries the points may be worn. There is a protrucing lug on the back of the base plate that looks like it should fit into a groove in the magneto shaft. This lug looks worn. I am wondering if this the problem. I have tried to time it many times but always end up with no spark. As soon as I loosen the spindle and and rotate the points so that the lug fits into the groove in the magneto shaft I have spark again but the points are not timed correctly. I am stumped. I am following the Haynes BSA A7 and A10 manual which has been pretty good so far.
Any ideas out there?
Title: Re: Ignition timing troubles A10
Post by: Brian on 12.03. 2011 04:44
I think you are going about it the wrong way Bill.

Turn the points plate so the little key on the back goes into the groove and do the centre screw up firm. That has to stay in that location and tight.

Then go to the other side of the engine to the auto advance unit, this has a bolt in the centre of it which is also the puller, undo the bolt until the unit comes loose. Now at this stage you need to have the engine at the required distance before TDC, I know the book says 3/8" but set it at 5/16". make sure you have the right cylinder on its compression stroke, both valves closed.

Next get a small piece of wood or something similar and wedge the auto advance unit in the fully advanced position. At this point you have to rotate the maggy in its direction of rotation until the points just start to open, there are all sorts of fancy ways to do this but the old fashioned fag paper works ok. Put the fag paper between the points and slowly rotate the maggy, when you can feel the paper start to slide out you are in the correct spot. Now push the auto advance unit fully in and nip up the centre bolt. Do this with the points up the top which means the cam ramp on the bottom is opening the points, this should give you the spark from the rear pickup to the right cylinder.

If you are in any doubt as to which side the lead should go turn the motor over until you have it on TDC compression stroke on the right cylinder, the points just opened in the maggy, take the pickups off and look in the holes with a small mirror. In one of the holes you will see a brass strip, the lead from the brass strip must go to the right cylinder.

Once you have set the timing go back and double check it as sometimes when you do the bolt up in the centre of the auto advance unit it can slip, you may have to go through the procedure a couple of times to get it right.

Hopefully between the book you have and this you will be able to get it sorted.
Title: Re: Ignition timing troubles A10
Post by: iansoady on 12.03. 2011 11:41
Agree with Brian. The points have to have a fixed relationship with the armature as they need to open when the armature is at the point where its coil is producing maximum current.

It is something of a pain getting the timing right when you're faffing about with the AR on the other side of the bike.
Title: Re: Ignition timing troubles A10
Post by: Bill18 on 14.03. 2011 09:30
Thanks Brian and iansoady. the Haynes manual had me undoing the centre screw on the points side so things were off rom the start. I spoke to an old BSA owner here on Sunday and he set me off on the right track (and lent me very nice little TDC guage that screws in to the sparg plug hole) but I am still having trouble with the other (advance) side. Every time I get the timing set up right and go to re-tighten the centre bolt on the RHS of the magneto I jam the automatic advance so that it does not return freely. It seems to catch on the last little turn of the bolt and starts to tighten back on the advance unit with the reverse thread. I am wondering if it needs a little shim to stop it going that last little bit. The centre slip-on washer seems pretty worn and may have lost some thickness.
I will redo it exactly as Brian sets it out and see how I go - using 5/16ths this time.
Thanks again for the generous advice.
Title: Re: Ignition timing troubles A10
Post by: Triton Thrasher on 14.03. 2011 12:25
I don't fully understand what you're doing, but, with the ATD off the bike, the centre nut (that looks like a bolt) should be screwed (leftwards) completely into  the outer yoke of the auto advance, so the quick thread on the nut is past the threads in the yoke and the nut can be turned freely in the yoke.  There is a theadless section on the outside of the nut, under the head of the nut.

Then offer the ATD with nut up to the magneto shaft. Keep a little outward pull on the ATD to stop the left hand quick thread catching as you screw the nut rightwards onto the shaft.
Title: Re: Ignition timing troubles A10
Post by: RichardL on 14.03. 2011 13:22

If you use the "Search" tab and search "horseshoe" you will find some posts about techniques for tightening down the ATD bolt while holding timing position.  A couple of these are from my being audacious enough to attempt advice (a little bit of which I actually think is decent). I grew to hate fussing with the horseshoe washer and used the tiniest bit of contact cement to hold it in place whiile working to seat the ATD taper without twisting the hard-earned timing.

Richard L.
Title: Re: Ignition timing troubles A10
Post by: muskrat on 14.03. 2011 19:00
G'day Bill18,
                all very good advice so far. I will add my bit, but it's been over 15 years since I had a magy.
Once I got the points opening at the right spot I would wedge the points plate against the cam ring with 1/2 a cloths peg. Then when the ATD nut was almost home I'd give the unit a light tap to seat on the taper then tighten the nut. If it slipped I'd start again but set the points plate a little advanced to allow for it. Opening or closing the points a thou or two can then get it spot on.
Ready to run for cover.
Title: Re: Ignition timing troubles A10
Post by: Bill18 on 15.03. 2011 02:37
Thankyou all for advice regarding tightening the RHS magneto bolt. I have fluked it sometimes but not really known why. I will try it exactly as described and let you know how I go.

This is an interesting project. I bought the bike in 1979 because I love old British bikes, BSA's particuarly. I had a Triumph Bonnie for a while when holidaying in England in 1975 and my firnds always had Triumphs and Nortons. Perhaps because my name is Bill I favoured BSA's. Having bought the bike and paid my $300 Aus. I rode it 300m down the road and it siezed. I pushed it home and pulled it right down ready for the rebuild. I then moved from Canberra to Perth - leaving the bike bits in my parent's garage. My father, an engineer and very good home mechanic, began to rebuild it. He got half-way and then he and Mum moved to Perth in 1990, bringing the bike with them. I took it up again - very slowly. Nearly there now, but alas Dad won't see it running. It is not completely original, bits were missing from the start and I am not sure what front forks it has - but it looks great in its new black livery. It also looks great beside my everyday ride - a gorgeous yellow 1997 Moto Guzzi Sport 1100.

Thanks again for the advice.

Title: Re: Ignition timing troubles A10
Post by: Brian on 15.03. 2011 02:52
Hope you get it sorted Bill, my BSA's also live in the same shed as a Moto Guzzi. I bought a 1000s new in 94' and still ride it, fantastic bike.
Title: Re: Ignition timing troubles A10
Post by: Bill18 on 17.03. 2011 09:34
Thanks Brian and others.
I fiddled again last night and still have the auto advance sticking when the bolt is fully tightened. Not sure what I am doing wrong. I now, however, know how to time the igition properly.
I undid the bolt until the advance unit came away After timing I held it back a little while tightening the bolt, I tapped it just before it fully tightened, I tried everthing a few times but alas the advance is still not returning freely when I release the wedge. I think I will try starting it anyway and see what happens.
Thanks again.
Title: Re: Ignition timing troubles A10
Post by: bsa-bill on 17.03. 2011 18:39
Hi Bill
My A/R unit sticks when turned by hand, apparently can be due to magneto and does not happen when the bike is running.
My bike runs ok so I think it cou1d well be right
Title: Re: Ignition timing troubles A10
Post by: Stu55Flash on 17.03. 2011 20:38
One part of the A/R, the frame bit that stops the advance going too far, is held on at the rear by a lightly pressed on ring. If this is too tight it makes the A/R a bit stiff. I know from bitter experience!

Title: Re: Ignition timing troubles A10
Post by: Bill18 on 18.03. 2011 01:07
Thanks again for advice. I haven't tried to start the bike yet and am going camping for the weekend. I will try it next week and see how things go before worrying too much more about the sticky A/R.
Thanks to Richard in Maida Vale who offered assistance. I could not get on to your personal message to reply. I am in Margaret River. Hopefully we will catch up one day when the bike is on the road.
Title: Re: Ignition timing troubles A10
Post by: Triton Thrasher on 18.03. 2011 12:09
Insufficient backlash at the pinion teeth can make the auto advance stiff.
Title: Re: Ignition timing troubles A10
Post by: Bill18 on 20.06. 2011 02:19
I haven't been on for a while.
On Saturday I sat down yet again and studied the valve movements and distributor gap opening - and this time it made sense. The valve timing was 180 degrees out. The motor had been put back together by my departed Father and he said I might have a bit of trouble at the end. I had tried reversing the plug leads before but without conviction. This time I knew it was the problem. So I changed them over, flooded the carby, gave a squirt of aerostart into th carby and kicked it and bang - she came into life after being quiet since August 1979. By the end of Sunday she was starting first or third  kick and idling within a minute. What a beautiful sound - an A10 burbling away through header pipes and no mufflers. I am sure my Dad heard it. Now the seat and footpegs and wiring and we will be on the road after 32 years.

Thanks very much to all who gave me advice. I was beginning to think I was never going to get her running but it just took time and finally understanding the workings of a four stroke motor. Once I had drawn myself a diagram of what was happening with each revolution I was on the way to understanding the "mystery".

Title: Re: Ignition timing troubles A10
Post by: A10Boy on 23.06. 2011 16:14
Great news. Well done! Theres nothing quite like the sound of a BSA in fine tune.  *smile*
Title: Re: Ignition timing troubles A10
Post by: Bill18 on 24.06. 2011 01:43
Thanks Andy. No there is nothing quite like it.
Title: Re: Ignition timing troubles A10
Post by: Topdad on 24.06. 2011 11:06
Well done Bill ,having just fired up my A10 for the first time this year I now exactly how you're feeling, I'd raise a glass to your old man as well I'm sure he'd be chuffed ,best wishes Bob Hebdon.
Title: Re: Ignition timing troubles A10
Post by: Bill18 on 25.06. 2011 03:33
Thanks Bob, I am sure Dad would be. My son is home from Perth for the week so I will start it up for him to hear and marvel and then I will get down to the oil leaks. My son has grown up from a toddler with the BSA always going to be running "by Christmas". He is now 26.