BSA A10 ignition

[KeithJ]

Interesting posts.  Looks like for my ally head A10 I will use 32/33 BTDC and the 24 Deg of advance will end up with 8/9 Deg at idle.  
What governs the Idle advance apart from the movement on the advance and retard unit?  I am tying to understand if it is worth fine tuning the A/R unit or is it just not that critical?
If it is not that critical, why the issue with the greater advance on using a Triumph A/R unit
ATB
KeithJ

[RichardL]

Reading all this is interesting, though, less useful to us folks just dipping a measuring device into the plug hole. Still, good stuff. Speaking of the auto advance mechanism, I'm into my timing case for a dynamo belt conversion and checked my home-made auto-advance return springs. Still good after about 3,500 miles.

So, I wonder what the heck happened to Fred in France, who started this phread (uh, "thread") in '07?

Richard L.

[Retired Fireman]

Keith J,
         What was happening with my engine was because the range of advance was set for a Triumph which the timing is 38 deg fully advanced the A/A unit (Auto Timing Device) advances from around 6-8 deg at idle to 38deg fully advanced (around 15-18 deg at the magneto) but when this unit is fitted to an A10 the timing is set to 32-33 deg fully advanced then the timing would retard to around TDC. A10's need around 11-12 deg (magneto) of advance so the timing was over retarding back to TDC instead of around 8-10 (crankshaft) that they need to idle properly, also the timing advance curve would be retarded through the advance range until near 3000rpm where it became fully advanced. My A10 started and idled good when cold but when warmed up the idle became unstable, as well the engine was lacking performance because the advance curve was retarded. After modifying the advance range in my ATD the engine was transformed and now idles with complete reliability in traffic when hot and runs very strong. If you choose to time your engine useing the broomstick down the plug hole method you don't know if the advance curve is correct and if it is over retarding back to idle or whatever. SRM sell a "strobe timing kit" which consists of a new crank spring nut machined to accept the alloy timing disk they supply Then all you do is remove the primary cover fit the disk to the crank nut with 2 allen screws supplied, find TDC (piston stop method is best to accurately do this) attach a strobe light with an external battery, clip onto either side spark plug wires and you can watch your advance curve happen and properly time you engine for optional performance plus check the timing between cylinders and if needs it adjust it in your mag. Hope this explains the importance of the correct ATD being fitted to your bike.

[KeithJ]

Appreciate your reply Retired Fireman.  Essentially, the difference between the two ATD's is the Triumph one gives about 5 Deg at tick over and the BSA one 10 Deg.  Also, this difference retards the advance curve.  Brilliant.  Apart from "Fully Advanced at 3000 RPM" what are other "typical" advances at say, 1000, and 2000 RPM?  With these additional key advances, it will be possible to confirm the correct springs are on the ATD?
ATB  KeithJ

[Retired Fireman]

Hi Keith, I cannot confirm actual BSA timing advance curve specs for A10's in advance to RPM steps someone here might know? In their day BSA didn't publish a lot of detailed info to the public they just gave a limited amount to dealers so they could make money out of us if we where not smart enough to figure this sort of stuff out ourselves. By me building up the retard side of the ATD 's lug or ear to limit the amount of advance I essenually tightned the advance springs as you can imagine, as long as the advance is all in (fully advanced) at around 3000RPM the curve wouldn't be too far wrong I think, if on the other hand the springs are too weak the advance would be all in before 3000 and essrentually over advanced too early in the RPM range that could cause pinging and possible over heating if you rode in that RPM range for a while. If someone on here has a 6v Boyer electronic conversion they could set up a degree disc and timing light and record what figures the boyer gives at 1000-1500-2000-2500 etc and share this with the forum. My advance curve is nice and even to about 2000 then it slows down to be all in at about 3000. P.S. my bike is an iron head A10 7.25 to 1 comp, 356 cam with late model flash biger port head and air filter running on 95 fuel, alloy heads with higher comp and 357 cam timing would I think be different so don't take my specs as across the board

[KeithJ]

Thanks for the post Retired Fireman.  Hope someone can post the advance curve details.  Returned from a run on my A10 and as the engine slowed and stopped when I got home, a strange tinkling sound came from the engine.  Have checked it and it looks like something significant has gone wrong inside the engine. Perhaps and end.  Ah well!!!!!!!
ATB

[muskrat]

Hopefully just the fins saying they've had fun (got good and hot). How far and hard was the run?
Cheers

[Retired Fireman]

Did the "tinkling sound" occure as the engine wound down, it could have "run on" a couple of revs because the plugs were overheated. Before the doom and gloom starts whip out the plugs and have a look at the electrodes to see if there is any sign of overheating on their tips, your ignition timing might be a little advanced or you have fitted the wrong heat range of plugs. In my iron head A10 I run NGK --7ES (I'm at work and nearly finished a 12 hr shift and can't think it could be BE) If you have an alloy head check the correct heat range you have fitted and of course the gap is correct. By the way SRM recommed 35 degrees for alloy heads and 33 degs for cast iron according to their website. Let us know if you find out what the "tinkling sound" was, I will be away from the Forum for 2 weeks as I am riding my 57 A10 up to the Queensland BSA club's "All British Rally" near kingaroy in Qld then returning via a few friends homes about 3000 k'm so will blow the cobwebs out of the old girl. Will check on your progress on return good luck!

[Retired Fireman]

Just another thought: have you had your ignition checked with a strobe light on BOTH plugs? I have seen 5 degrees plus variance between the two cylinders and if you have set your ignition on one side and not checked the other, the cylinder on the other side could be 38 BTDC and the one you timed it on would be 33, that would heat up the other plug and possibly cause the "running on" that is the tinkling sound when the engine stopped. Or maybe not (GULP!)

[KeithJ]

Have a good run.  Sounds like a lot of fun.  Be interested to hear how the run went, weather and all.  Bikes been running OK for years.  Plugs look fine, still makes the sound just turning it over on the kick start.  Will be a few weeks before I get to look at it further but will let you know what I find out.  Due end of September to collect another bottom end, roller conversion, cases, new rods and pistons etc so aim to rebuild that.  Will check timing on both cylinders.  Good point.  Will get the old girl re-painted as she is in need of it. ATB

[muskrat]

Ah, the sound you hear when winding the motor over is the backlash in the timing gears. At one point in the revolution the valve spring pressure tries to push the cam backwards and reverses any play in the gears. Sort of a clinking sound.
I agree with RF that it might be running on when you turn it off, and you would hear the above sound as well as piston knock. If it's caused by incorrect or uneven timing a new SRM bottom end won't fix it.
Cheers

[Retired Fireman]

As Mr muski sezz it could be the clearence between the immediate, main pinion and cam gears causing the racket, throw in wear in the intermediate gear bushes in the inner case and crankcases plus a bit of wear in the camshaft bushes and you would have a synphany of clickingness as the camfollowers change the direction of thrust on the gear stack clearence as each cam goes over the top ramp of it's cam lobe. Triumph twins suffer badly from this because they have two camshafts and the gears were individually selected when new to run quietly together but along the way they either wear or get subsituted with timing gears that don't match. BTW if you are forking out for a roller bearing conversion and new everthing have a look at the SRM timing kit with spring crank nut so you can accuratly time the engine and check advance curves as well as timing between cylinders, but before you do be EXTREMELY carefull establishing TDC when setting up the pointer on the disc, don't forget as the piston stops momentarly at the top of the stroke the crankshaft is still moving and it takes very little movement to give a few degrees either way in crank movement. An excellent discription and a few methods on how to establish acurate TDC is on a car engine site "ISKY CAMS" it explains how to do it dead acurate and how to check your TDC with a degree disc and the "piston stop method" I turned up an adjustable "piston stop" that screws down my drive side plug hole and locks the piston in 33 deg before TDC, I carry it in my tool kit so at anytime in the field I can quickly and dead accurately put my engine in 33 deg BTDC for checking timing as well as establishing a pointer at TDC. Hope all this info helps.

[KeithJ]

Constructive posts, thanks.  Noise I have is the same as taping a cylinder fin.  A clear bright sound. Interesting to me it happened just as I got home.  I'd switched of the petrol and was just running the carb dry.  Perhaps just coincidence.  I will find out when I look further in to it.  The new roller bottom end is in another set of cases.  It was already underway and not being done to sort out this problem.    ATB

[duTch]

 I was searching for 'ignition related' and found this maybe should do a new post, however...??

 

a strange tinkling sound came from the engine.

  Ok Tinkerbell (Keith J)...don't do a 'Phread' on us and keep us 'Guesting'......I just read through this whole phread, and don't know what was the 'tinkling'...
Maybe it's in another 'Fread'?

 Generally I do the measuring stick down the hole, but while replacing my cush drive spring the other day, I made a rudimentary degree wheel from a plastic container lid to screw onto the crank end (see photo), and roughly checked my timing which was about  ~20˚, so with a bit of play in the CB plate key, moved it ~10˚ to ~30˚ btdc was running fine before with only a bit of occasional miss, and seemed fine when I set off for test ride yesterday, as usual starts first kick, got about a mile up the road and setting off from lights, went into splutter mode and conked out- started after a bit but only another block and stopped completely, played with plugs and usual stuff- pushed home, had beer, and still no (very minimal) spark/no go.

 Finger-in-pickup-hole-spark-detector- nothing much....

Checked and cleaned Earth brush and slipring and other brushes, one behind CB plate had grease on, after which managed to achieve a splutter or two

 Maggie rebuilt in late nineties by (legendary) Les McKitterick, who assured me it will outlast me.. , before sitting till a year ago and  has only done ~3000 miles since.

  Found the 'points retaining clip' broken and missing, (see other photo) is this otherwise important, and, if it was flapping around in the housing- is there likelihood of shorting or de-magetizing anything...???

 Any other clues I haven't thought of, maybe condenser which I'm sure he replaced....maybe need a brightspark??

 Cheers in advance, that was epic- need refreshment!

[duTch]

 Ok, I may have jumped the gun a bit (all three of 'em)....after playing and cleaning and measuring bits and ohms, threw it back together this morning, and first kick away she goes... .....
 Did a bit of a lap of the old block ~about 20 miles- seems ok, pops and splutters a bit here and there, but running as well as it did before so will just continue as per usual...see what happens tomorrow if I don't get scammed into workin'