I think I know the answer but i have a 98 250 Trailboss that has been sitting for a couple years. I tried to crank it a while back and noticed all of the gas was gone out of it. i put some in and then tried cranking again. Wouldn't start. i pulled the plug and it was absolutley soaked. I checked the compression while I had the plug out and it was about 130. I checked the drain in the bottom of the engine and found all of the gas! drained it. Figured the carb needed rebuilding so I put it back in the corner of the shop.

finally drug it back out, rebuilt the carb, put in fresh plug, new fuel petcock, clean the tank out, new fuel filter. darn thing still won't crank. got spark and fuel looks good, not soaked. I rechecked the compression. it is between 90 and 100. I was running great when parked and the comp was 130 before......i'm thinking crank seal. would a bad seal cause drop in compression?

 

If you've rebuilt the carb (cleaned the jets and new needle and seat) plus have fire and have completely drained the crank case of excess gas, but compression has dropped,I would pull the front clutch and you might find the crank seal either distorted or can even pop out! I've had this happen before especially on machines that have set up with the fuel valve left on. Gas just distorts the seals and will leak, loosing bottom end compression. Seals have to be good to allow compression of the gas/oil mixture back up through the transfer ports into the cylinder to be able to run. Plus if the clutch side seal is bad then the one behind the stator will need to be replaced also. OPT

 

the fuel valve was bad (i just put on a new one) so the crankcase may have had fuel in it for a long time while it was sitting. I'll just go ahead and plan on replacing both seals. I kinda figured that is what it issue was.....Thanks for the reassurance