Starting trouble

[clive]

Dick: I will drain oil later today. No, my SR-1 hasn't attached this unit, the auto A/R. With this bike ignition timing is adjusted by getting the magneto lobe to a position where the contact points just start to open (1/2” before TDC). This is achieved by slackening the magneto drive sprocket and slightly rotating the drive shaft, which carries the lobe, until the lobe opens the contact points at the desired moment.

Regards, Peter

Peter, all AMC singles fitted with an SR1 mag should have the illustrated auto advance fitted. Are you actually rechecking the timing after you do the adjustment in the described manner? The reason I ask is because with both SR1 mags with the auto advance and N1 mags without I have found that the timing has a habit of slipping as you tighten it up if using the magneto sprocket as the loose one. I always tighten the mag sprocket and loosen the sprocket at the exhaust cam end to allow making the timing adjustment. Doing it this way allows you to gently tap the sprocket to ensure it is locked on the taper before tightening the nut. I still always recheck the timing and once in a while it has slipped as I have done it up. 1/2 inch before TDC will mean your bike is always on full advance. Whilst some bikes will start on full advance all my singles require retarding to start. So this may remain your problem until you retime to perhaps 3/8 before TDC and see if it starts.

[Dixter]

Hi Peter: Your timing looks right to me.

When I first saw your IMG-1499, I was uncertain. Apparently, the crankshaft had rotated 360 degrees from the starting point, and this was a 'view' I was unfamiliar with. I pulled out Mr. De-Groome's article and followed the "3 dots" section using some parts I had on hand. When I rotated my "mock-up", I arrived at the same point as you. I believe you accurately followed the article and am confidant your timing is correct.

If you have the proper clearance between the pushrods and the valve rockers, this engine should have sufficient compression to fire a combustion chamber filed with air & fuel.

1. Have you measured the Compression Chamber Pressure and if so, what are the results?

Finding the Compression stroke using a thumb is sufficient. Checking the push rods is "double-checking", which is always good.

An engine will fire without a carburetor, you only need to get the correct air/fuel charge in the cylinder, and at this stage, I do not recall this bike have demonstrated combustion. I would focus on getting the ignition timed correctly. The lack of the Auto Advance device is a shortcoming, not a "show-stopper". The bike should start and run at full advance, it just may not want to idle, or pull from low RPM, and it may "kick-back", fire, or give some indication that the engine is able to run.

Here is my "mock-up".

Here is your engine 360 degrees after inserting the cams. Our results agree, IN = approximately 10:00. EX = approximately 14:00

01_IMG_1499b.jpg

Best wishes,
DC

[spookefoote1956]

Anyone fancy a trip to Germany?

[spookefoote1956]

Tippi is the carb completely clean? I had a lot of trouble with my mag and changed to electronic ignition. I'm not suggesting that you do that but if the carb's clean, timing's right, pushrods are rotating freely and the mag's giving a good spark you should get some kind of a bang; even if it's just a backfire.

Could you please upload a picture of your mag from the points side and also from the sprocket side with both covers off. Could you also confirm that there is or isn't a lever to advance / retard the timing.

Cheers, Chris

[tippi11]

Dixter, Dick: Understand what you are saying - many, many thanks for your effort with the mock-up and related comments. I will get a compression tester tonight from a local workshop. Hopefully I can report the results by tomorrow.
Spookefoote1956, Chris:Thank you - I will take pictures of the magneto when I am back in the garage to do the compression test.
Best regards, Peter

[tippi11]

Hello,
Please find below 3 photos:

-SR-1 magneto, both sides
-compression ratio, results/print-outs compression tester

Regarding compression ratio: shown are the results of 3 measurements - lines 1 and 3 on left hand print-out (forget line 2, my fault) and line 1 on right hand print-out. The values vary between 5.8 and 6.2 bar. Assuming that the compression tester itself was ok and some measurement inaccuracy can be considered normal, the compression ratio is something around 6 bar.

Please let me know your comments, thank you.
Regards, Peter

[spookefoote1956]

Isn't there meant to be an ATU at the timing side?

[SPRIDDLER]

Isn't there meant to be an ATU at the timing side?

Do try to keep up, Spooky Peter's already told us there's no A/R of any sort (i.e. neither manual nor auto)

[spookefoote1956]

That wasn't what I was asking. I know there isn't one, what I was suggesting is shouldn't there be one.

[SPRIDDLER]

That wasn't what I was asking. I know there isn't one, what I was suggesting is shouldn't there be one.

Peter, all AMC singles fitted with an SR1 mag should have the illustrated auto advance fitted.