I picked up an old trailboss and I know it's from 87'-92'...baught from a friend who ran it then blew it up and would no longer run...they baught a piston and installed it (that's as far.as.they got, I brought it home with the top end already apart) I had baught rings and reassembled top end and everything else, and now it will not even fire once...been using starter to turn over(had no battery, has been running without one prior). Tried thoroughly cleaning carb...have good spark( new plug), won't even fire on ether...could rings be stuck in piston to prevent compression? I'm at my wit's end here....

 

cylinder or head, possibly both, are warped im betting..take it to a good machine shop to get it checked out if you are not sure how

 

Check compression to see where you stand. Normally you can't just "stick a piston in it" and expect it to run properly. Cylinder needs to measured for the correct over size piston and has to be bored and honed to fit. While you're at it replace the crank seals as this can keep one from running also. If it won't even fire up on ether that's telling you something there.

 

Thanks for the reply both of you...I have honed the cyl. And measured it, and it measures 72.15, and the standard piston size that I have is 72mm so I am safe there...I've had the head and jug checked and they are not warped. But I decided to put everything back together and tried again, still nothing. So now I am going after the crank seals after what you both said, and reading a bunch online. I want to know though if it is possible for crank seals to go at once? or if it is always a gradual thing?because from what I know the machine ran fine then there was a kind of poosh sound when it died...and the piston blew up...could that destroy crank seals?? What do you think?

 

Crank seal behind the drive clutch is the one that gives the most problems. Look at this video on cylinders and how to measure piston to cylinder clearance.You can even check clearance with feeler blades if you don't have micrometers.Look at 7:25 on the video.