Running issues

[G3L1946]

Good morning to all,

Just, finally, completed the restoration to the firing up stage ( after a few misfires and injuries! ).
I’ve had to fit a new, replacement carburettor ( from Amal ) correctly set up with jets etc.
I’m having real problems getting the engine to run at a consistent idle speed. I’ve followed the Amal tune up instructions but not getting too far solving the problem. I get the engine to run at about the right idle speed but after a while speed increases or decreases especially after employing the throttle. Inspection of the plug shows no evidence of over rich or weakened mixture although the exhaust does produce a bit more excessive smoke than I would expect but not over the top.
The engine starts easily on first kick. However, the valve lifter, although appearing to be operating correctly, will not stop the engine and has no effect. I’m pretty confident that timing is correct and there are no air leaks. Any pointers would be most appreciated. If I’ve missed anything out trying to describe this then, hopefully, I can fill in the gaps!

Steve

G3LS , 1955.

[Andy G]

Might be air leaks? Try spraying a little carb cleaner or wd40 around the carb base and see if the tickover changes.
Can't think why valve lifter won't stop engine...if it lifts the valve it is physically impossible for the engine to carry on without compression!
Are you sure that the valve actually lifts? Operate the lever while watching thru the valve cover.

[spookefoote1956]

Is the cable actually lifting the valve?

[G3L1946]

Hi,

No evidence of air leaks, carburettor is tight but not overly so as to cause distortion. However , will test and check tomorrow. Just removed rocker box cover to tappets and note that nothing moves when activate lifter arm. Stumped now! Any ideas or am I missing something obvious? The lifter arm is moving, so I’ve been wrongly assuming that the valve has been lifting, but it seems it isn’t.

Steve

[G3L1946]

Morning,

The actuator arm seems to slide in and out only being held in place by the external spring. For the life of me I can not understand how it operates. I’ve searched for a diagram which shows it in place and how it operates but to no avail. Does it operate by lifting the cam?

Steve

[Andy G]

See images in linked discussion here:

viewtopic.php?p=241260&hilit=Valve+lifter#p241260

Oh, wait...that's your own earlier thread!

[G3L1946]

Andy G

Correct! Thought I had it sussed but I hadn’t! Just hoping this won’t develop into some medium sized overhaul. The arm just doesn’t seem to be engaging with anything but just moves freely from end stop to end stop.

Thanks,

Steve

[Andy G]

Sounds like the lifter shaft might be excessively worn? Is there still an obvious flat side where the mechanism is "relaxed" and therefore valve closed? If you disconnect the cable, you should be able to rock it by hand to feel the resistance as it tries to push the rocker? If so, you should be able to prove the mechanism using a spanner before you reset the cable position?

[G3L1946]

Hi Andy,
Attached photo is the arm and the flat side still appears to be in good shape. There is a small amount of ware that can be seen but I doubt this is sufficient to cause a problem. I’m assuming it’s the correct part ( for a 350cc 1955 G3LS ) hence the rule. Releasing the spring and moving the arm in the correct direction results in a dead stop. Application of more pressure, no movement. It would be handy to know at which point of movement the arm starts to lift. At the beginning of its travel or further on?



Steve

[G3L1946]

Additional of ware.