Could it be the carb?

bobber · Post by **bobber** » Tue Oct 09, 2007 4:40 pm

Many thanks to you all for the advice provided; it's all starting to make sense but I am now not sure that i have timed the mag correctly. I set the piston at TDC, rotated engine backwards and lowered piston 1/2" then fully opened ignition control lever (cable taut)and set points to position where they are just opening. If I've understood correctly, I should have fully closed the ignition control lever (cable slack).

Biscuit · Post by **Biscuit** » Tue Oct 09, 2007 4:47 pm

You have set the ignition at the correct distance before TDC (some books say 7/16" but at full retard, this means of course that when advancing the ignition it is attempting to fire well before the appointed time.

So you need to retime with the lever fully forward, ensure the cable is fully slack, as there is a stop on the camplate that fixes the fully advanced position.

bobber · Post by **bobber** » Tue Oct 09, 2007 5:00 pm

Thanks again for all the advice; it's been really helpful and significantly boosted my enthusiasm to get at it and get it going! Regards, Andy.

Don Madden · Post by **Don Madden** » Tue Oct 09, 2007 5:46 pm

Did you say in the first post that you couldn't get the engine to turn past compression & you positioned the kick lever using the clutch?

You must position the piston just past top, after the compression stroke, using the exhaust valve lifter or you are unlikely to get it to run through & will experience exactly what you describe.

Be sure the valve lifter cable is adjusted correctly & is acually releasing the pressure in the cylinder.

Cheers, Don.

SPRIDDLER · Post by **SPRIDDLER** » Wed Oct 10, 2007 12:35 am

Yep, you need to correct the timing / lever setting as above but it is unlikely that you have so much compression that you cannot turn the engine over TDC at all.
If the valve lifter is working is should prevent any noticeable compression.
Try keeping firm pressure on the kickstart and see if it gradually 'sinks' down and rotates the engine past the compression stroke.
If it doesn't it could be that the kickstart quadrant is worn (a common and not catastrophic situation) and that the kickstart is jamming - a mechanical jam and not a compression lock at all.
Just a thought.

bag-o-nails · Post by **bag-o-nails** » Thu Oct 11, 2007 10:27 am

i did notice in your post someone else built the
engine and you assume the valve's were correct
it might be worth checking them, if they are too tight when she spits back does it chuck out fuel through the carb air intake
high comp, spitting back (Valves)
cheers b-o-n

itma · Post by **itma** » Thu Oct 11, 2007 11:04 am

This is definately a kickstarting technique problem B-0-N, allied to confusion with the advance retard.
Even a well set up one will kick back if you are timid on the pedal.

bag-o-nails · Post by **bag-o-nails** » Thu Oct 11, 2007 11:19 am

Thanks Itma, it was just a thought
it would seem to be quite a Knack then

cheers b-o-n