I have searched and searched but could not find the answer. Could somebody tell me what the compression should be on the 250 motor? It ran fine last time I used it. Next day would not start. It has spark but seems weak and when you put a finger in the spark plug hole the compression seems low.

 

Id say it should run anything over 100psi. Maybe even less than that. The one I rebuilt had right at 200psi after break in.

Check your intake valve lash. They are bad about wearing at the face and tightening the valve lash, which will eventually hold the intake valve open enough to lose compression. Could be that is your issue, but usually this happens over time.

Sounds like it could also be a spark issue though if you think it looks weak? Is the battery good? Have you had any other electrical issues with it?

 

Thanks for the reply. It is my son's quad but i drove it to see how it was running. Did an easy 22 mile trip. Ran ok except for a little bit of carb problems. Shut it off at end of trip and it has not started since. Does not even fire when I put gas in the spark plug hole. I can hold the spark plug while cranking it over and hardly feel the shock. Battery is fully charged and cranks good and long. Just seems strange that it would quit after shutting it off.

 

According to my Clymer's manual compression should be between 142-199psi. Minimum compression should be at least 114psi.
HTH,
Mike

 

Problem turned out to be intake valve. Set the valve to .004 and it started up in about half a crank and purred like a kitten. I still think spark is weak so a new coil is on its way. Now I have just two more questions. When I took the valve cover off some oil dripped out. What tyoe of oil do I add back and how much?

 

Glad it was an easy fix. My '96 250 says on the filler cap"10w40".
Mike

 

Wow, you must still be of the "bullet-proof" age!

There is a very good chance that your coil is fine, but your plug cap
resistor is shot. These old coils (TEC?) are pretty robust, but the cap
resistors don't last indefinitely. You can open it up and replace it
with a piece of metal. BTDT.