Hi All,
I have an AJS 1963 350 16 Short Stroke. I have just had to torque the head bolts after an engine rebuild. As you know this requires to position the piston at TDC remove the rocker box for access. Then reverse the process. After refitting the rocker box and adjusting the tappets to a little freer than recommended, because the engine is cold. I tried to move the piston by hand pushing on the kick start lever, I found the engine locked. No movement at all. The gear box is in neutral. I wound the push rod adjustments back so as to be able to see if the tappets had jammed. They both moved freely. I was able to use a light to see both tappets were touching the valves correctly. Holding the push rod out of the way I was able very slowly to move the piston. I then repositioned the piston to TDC. Then I wound the push rod adjustments out again. The engine was locked again. So obviously the valves are not moving. I am at a loss as to what to do next. All advise is greatly appreciated.
Thanks heaps Malcolm
Not sure I am an expert, especially on short strokes but here goes.
Some questions first to help with diagnosis. You say it is a rebuild. Was the motor running before the rebuild, did you replace the pistom?
My immediate thought is that the piston is the wrong one and the valves are locking on the crown. Would not really explain the symptoms though.
A totally sideways thought is that it's actually the kickstart quadrant that is jamming and it's actually all free! Have you tried turning the engine using the clutch basket or rotor as the rotational force? To avoid taking the primary cover off could you try using the clutch pushrod adjuster to turn it with? On the Burman boxes it's not unusual to have to grind back the first tooth (or even the second if it is really worn) on the quadrant, not sure if the same fault occurs on that AMC box.
Richard Mills wrote:Clive,
Both valves only shut at TDC if on compression stroke.
I assumed it was on compression TDC as i assume the removal of the rockerbox requires no pressure on the rockers. Of course if it was
on the other Tdc the exhaust valve would be shutting and the inlet valve opening, but there still ought to be clearance if correctly timed.
Im not knowledgeable on the short stoke engines either, but another guess. Some pistons have different sized cut outs for the valves, maybe the piston is in back to front
Hi All,
Thanks for your replies. I have done some more investigating and by using a bright light I was able to see the valves and springs more clearly. I found in my hast to refit the rocker box I cracked a guide. My guess is it is so tight in that area the inlet rocker must have got hung up on the valve and I just put too much pressure on it. Until I got involve it was running beautifully.
Thanks again for your advise. Cheers Malcolm
