Locking up

B

builderpete

Member
I am not a mechanic just someone who loves playing with small engines. I have a craftsman / powerbuilt 15.5 500cc i/c engine. I have just put a new / used connecting rod on. The camshaft was in good order. but the shear pin to the lower spindle on the flywheel was broken and the flywheel was 30% out of line. I replaced the shear pin . Now when I turn the engine over without a spark plug the crankshaft spins at a good speed. When I replace the spark plug the engine spins and stops in the same place. Am I looking at valves, timing or what? Any help will be greatly appreciated . Remember I'm a chancer so explain clearly please.
 
Lets start with the engine model type and code so we can see what engine you have. At this point we don't know if you have a flat head, OHV, OHC, or some new fangled aerospace valve system.
 
First adjust the valves. Exhaust rocker is the one closest to the flywheel.

IN .003-.005
EX .005-.007

Now with the valves adjusted rotate the engine thru at least two complete cycles whiel watching the intake rocker. On one cycle both valve will be closed but will be a slight movement of the intake as you reach TDC Compression stroke. IF not present the cam ACR is broken and the camshaft would need replacing.
 
Thanks I will try that. Also I have read that the piston should be 1/4* past top dead centre. Is that 1/4* the piston has to go down or is that the flywheel must rotate 1/4* further. Thanks for your help.
 
builderpete said:
Thanks I will try that. Also I have read that the piston should be 1/4* past top dead centre. Is that 1/4* the piston has to go down or is that the flywheel must rotate 1/4* further. Thanks for your help.
Click to expand...
1/4 inch past dead center on power stroke. Both valves closed. The idea is to bypass the compression release when adjusting the valves. But most people will rotate the flywheel to one valve is open and adjust the other valve.. Rotate the engine to open the opposite valve and then set that one. Which is basically when you do on a multi-cylinder engine with manually adjustable valves.
 
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