Starting trouble

[Dixter]

Peter, remove the spark plug to removed the difficulty caused by piston compression. Carefully rotate the crankshaft by turning the nut on the small timing pinion. You may rotate the crank in either clockwise or anti-clockwise direction. Take care not to loosen the nut. It has a left hand thread.

Once the lobe of the cam is pointed towards the ground or floor, the cam will easily extract. You will understand the problem in a fraction of a second. Ein Augenblick...

Ciao,
DC

[tippi11]

Dick,
I made it - cams are out, out, out!!! One of these lucky moments when crawling on knees results in the expected "solution"
Thank you very much, best regards from the Baltic Sea,
Peter

[Dixter]

Peter, AMC made numerous changes to the timing marks on the cams, over the years. Couple this with never being certain exactly which year cam has been put into an engine.

The best means for getting the cams correctly timed is in this article at Jampot.

http://archives.jampot.dk/technical/Gen ... e_Dots.pdf

Grüß from Seattle and occasionally Bayern
DC

[tippi11]

Dick,
I inserted the cams according to this article (I have the 3 dots variant) - will see what happens tomorrow after finishing the magneto/firing point adjustment and give it a kick start try.
Regards,
Peter

[Dixter]

Peter, I was suspicious about the cam timing all along. I'm betting the bike fires within 3 - 4 kicks.

Best wishes,
DC

[tippi11]

Dick and all engine experts,
Unfortunately it doesnt fire. This means I stand at the very beginning regarding possible reasons - ignition timing (which I checked several times), valve timing (which should be ok since I followed the article mentioned before) or carburettor incl. fuel supply.
The carb. came with the bike, float level and jet sizes are ok, apart from the pilot jet which is 25 instead of 30.
Is there any method to check whether the engine combustion chamber is filled with the air/fuel mixture? Or do you think there might be an air leak somewhere in the intake channel or the carburettor itself? During kicking there is a suck noise at the carburettor, but I cant verify the "quality" (is it good enough to produce the mixture and fill the engine).
Any hints and suggestions are very, very welcome.
Regards, Peter

[spookefoote1956]

Is the plug wet when you take it out and check it? When the engine is at TDC do the pushrods rotate freely without any lift? Have you got the advance retard lever (if you have one) slightly retarded? Could you take a photo of the timing side with dots with the engine at TDC? Don't worry, I went through this very same problem and eventually all came right!

[SPRIDDLER]

I haven't noticed what year or exact model is your bike. It might help to know this and add this info to your 'Profile' to save responders searching your posts?
Assuming ignition and valve timing are correct.......
As said above. Push down the carb tickler until petrol dribbles out. Dry petrol off tickling finger. Operate the choke to richen the mixture. Kick over half a dozen times. Plug should be wet with fuel if the engine hasn't fired.
Second. Remove plug and open the gap to around 2mm (0.080"). Reconnect HT lead and place plug on a metal part. Kick engine over and you should get a strong blue spark. With a magneto that is in tip-top condition you should still get a good spark at kick-start speed when the plug gap is 4mm. Return gap to normal (about 0.65mm).
The magneto will produce its strongest spark if you set it at at Full Advance (assuming that you have a manual Advance/Retard magneto).
Third, and as a last resort and simply for the pleasure of hearing some sort of response from the engine and to know that the plug is firing under compression, remove plug, tip a teaspoon of petrol into the plug hole, immediately replace plug and kick over.

[tippi11]

Hello,
Thanks a lot - I will follow your suggestions tomorrow.
Spookefoote1956: A photo of the timing side may be a bit tricky, because I am unsure that one can identify the dots (thanks to my camera)
SPRIDDLER: Model is late G3 swinging arm, duplex front frame variant, engine number is 56/16MS28374.
Regards, Peter

[SPRIDDLER]

SPRIDDLER: Model is late G3 swinging arm, duplex front frame variant, engine number is 56/16MS28374.
Regards, Peter

O.K. So just to clarify for future reference, from the engine number it's not a 1956 Matchless G3 but a 1956 AJS 16MS (or at least the engine is for a 1956 AJS 16MS). The 'G3' model was a Matchless of the 1930/40's mainly with rigid rear suspension, girder front forks and the magneto positioned behind the cylinder and above the dynamo. A 1956 bike (Matchless and AJS) has a very similar engine but it will (should) have an automatic (not manual) Advance/Retard type magneto positioned in front of the cylinder.
Later edit:
In your first post in this thread you wrote:

........ the engine occasionally makes a loud “bang” and a gas cloud comes out the inlet side (something like an external combustion). The most obvious thing on inspection: the inlet side of the carb. is fairly wet (petrol).

You also wrote that it does not have auto A/R so you should set the timing with the mag fully advanced and I assume you know which way to move the lever for full advance. However, if your engine has auto A/R as it should for 1956 (or am I losing the plot?) you will have presumably read the manuals and fixed the bobweights in their 'fully advanced' position when setting the ignition timing.......
It would seem to me (I'm still catching up with this thread) that the engine may be a mix of different years (and possibly has cams with markings that are not necessarily correct).