The BSA A7-A10 Forum

Technical => Lucas, Electrical, Ignition => Topic started by: maximus79 on 04.06. 2019 20:31

Title: A10 plunger 1951 timing
Post by: maximus79 on 04.06. 2019 20:31
Hi, I have just fully rebuilt a 1951 a10 plunger and cant seem to get the timing correct!!

The mag has been refurbished and a brand new amal carb, valves and guides, new leads and plugs.

It starts ok, and runs good until its opened up then it spits and misses!

Does anyone know the best settings?..

Many thanks

Max

adm edit: converted text, from SCREAMING (capitals) :O)
Title: Re: A10 plunger 1951 timing
Post by: muskrat on 04.06. 2019 21:00
G'day Max.  *welcome*
You either have a heavy typing finger or the caps lock is on  *smile*
Manual or auto advance?
Cheers

ps: I'll now move this to the correct section.
Now go to Introductions and tell us about yourself and bike.
Title: Re: A10 plunger 1951 timing
Post by: maximus79 on 04.06. 2019 21:48
Hi , sorry about that.

Its auto timing, with the centrifugal advance/retard cog on the end of mag, arent they all like that on the a twins?

ta
Title: Re: A10 plunger 1951 timing
Post by: muskrat on 05.06. 2019 00:50
G'day Max.
Generally the iron head models (gold flash) have auto, the alloy head (SS,RR,SR,RGS) have manual advance.
Check at the auto advance unit that the bob weights can move outwards against a light spring pressure and spring back when released. Then check the points move when the bob weights are moved outwards.
There's plenty of info (posts) on how to adjust the timing. Make use of the search button.
Once we eliminate timing we can then turn to the carb.
Cheers
Title: Re: A10 plunger 1951 timing
Post by: Slymo on 05.06. 2019 05:49
Sounds like fuel possibly? Also if it does have an auto advance make sure you are setting it with the bob weights extended so that the advance you are setting is the maximum.


Title: Re: A10 plunger 1951 timing
Post by: Rex on 05.06. 2019 09:22
Did you time it at full advance?
Title: Re: A10 plunger 1951 timing
Post by: muskrat on 05.06. 2019 11:04
G'day Rex.
Yes. Bring the piston up to 5/16" btdc. I use 1/2 a cloths peg to wedge the AR to full adv with the unit off. Set the points at 1 thou and wedge the points plate with the other 1/2 peg on the points plate (the peg that holds the spring) to the cam ring. Then shove the AR unit on. Check it again and again after a few turns of the motor. You may find it has moved so may take a few goes fudging for the movement whilst tightening the AR nut.
 *pull hair out* enjoy.
Cheers

ps: I luv my electronic ignition.
Edit. sorry I saw Max but it was Rex
Title: Re: A10 plunger 1951 timing
Post by: RDfella on 05.06. 2019 15:41
Musky - don't understand the 1 thou points gap. Was that a typo? Surely should be .012" otherwise the timing will be over-advanced when points are later set to what they should be.
Title: Re: A10 plunger 1951 timing
Post by: bsa-bill on 05.06. 2019 16:09
I expect Musky will reply but, I think your mixing up the points gap (maximum) and the points just opening for timing purpose, 1 thou or the thickness of the proverbial cigarette paper
Title: Re: A10 plunger 1951 timing
Post by: RDfella on 05.06. 2019 19:39
bsabill - you are probably right - guess I mis-read what he wrote. 'setting the points gap' made me think of actually adjusting them to that clearance.
Title: Re: A10 plunger 1951 timing
Post by: Greybeard on 05.06. 2019 19:59
Yes, it's worth mentioning again that the points gap affects ignition timing so they need setting before the timing.
Title: Re: A10 plunger 1951 timing
Post by: muskrat on 05.06. 2019 20:47
G'day RD.
Yes I just meant points just opening at the correct firing position.
Yes points total gap should be set first at 0.012.
Cheers
Title: Re: A10 plunger 1951 timing
Post by: maximus79 on 09.06. 2019 09:43
thanks guys..its weird because after the rebuild and mag being reconditioned, the bike went really for about 20 miles..then it shot a flame through carb and conked out! every thing is new on bike...

could the mag cog be slipping on the shaft as its a taper fit without a key?

also..is the no 1 cylinder the timing side?
ta
Title: Re: A10 plunger 1951 timing
Post by: muskrat on 09.06. 2019 10:15
G'day Max.
It is possible but unlikely for the pinion to slip om the taper. Quite often they will slip a little when doing the nut up.
Most here prefer to call them left and right cylinders. In general engineering terms left is #1, right is #2.
Have you gone through the checks I suggested?
Cheers