I decided to tear down the bottom end while waiting on parts, noticed when i split the cases, there is only small amounts of sealer around bolt holes and on other openings and around the rims, and no gaskets, there were no leaks previuos, is there supposed to be gaskets? or can I just use hi temp silicone or do I need to?, when I reassemble. Any help would be great Thanks

 

No gasket. Use either Three Bond 1134 or Yama Bond type semi hardening sealant. Basically what the factory uses,but they used it pretty sparingly,I just used a lot to make sure there were no leaks,and peeled off the excess off the case after it dried OPT

 

Thanks again OPT, another question bout the 250, when i removed the flywheel cover, quite a bit of oil came out, might be a dumb question, but is it supposed to be in there? if so what type and how much?. 1st time bottom ender, want to make sure I do it right and only once! Thanks MZJR

 

If you ordered crank seals with what other parts you ordered then you're ok. Not supposed to be oil in the stator/flywheel area. Leaking crank seals are the problem. If you're rebuilding the bottom end,have a new rod kit installed,don't just replace crank bearings only on a 25 year old atv. OPT

 

Yep crank is goin to the shop in the morning to have the new connecting rod installed, Thanks again for all your help!

 

Hello, finished the rebuild on the 87 trail boss 250, crank bearings, connecting rod kit, crank seals, bored .40 over, new piston and rings, followed the break in procedure per manual, this thing still does not run right, starts right up,no vibration or engine noises,(so I did something right) idles fine, but when you get past maybe half throttle, it misses like its hitting a rev imiter, falls on its face!!, cleaned the carb again, has the stock jet, air cleaner like new, float arms are level with the carb body, I am at a loss, any help would be great Thanks

 

There is a reverse limiter module under the fuel tank area behind the air louver on the tank. Right next to the regulator/rectifier Try disconnecting it and see if it runs any better,could be shorting out and limiting in forward. If this doesn't help you might pull the fuel line from the fuel valve and see if fuel flow is good from the fuel valve. Could be partially blocked not allowing enough fuel at higher speed.. Plus make sure the fuel cap vent is open. OPT

 

OK unplugged that box, took care of the rev issue, runs great when you keep the revs up, but when you go to stop and then go again, it boggs out and stalls, fuel lines clear, vent tube clear, new fuel filter, thought i really had it this time, any more ideas? Thanks again for all of your help, its greatly appreciated!!

 

The little 250 piston port engine even when its running tip top will have a slight bog for the simple fact it's a first generation two stroke engine,unlike the later generation reed valve engines If the bogging is really bad when you take off you may try to experiment with the carb needle position if you have ruled out any float level problem,needle and seat,etc.
Just drop the needle down a couple positions to lean it up and see how it runs on take off. If runs worse,go the other direction. Plus the stock main jet was a 145 and you could try dropping to a 140 and play with the needle position. It's not unusual on an old engine to have to change jetting when you rebuild one. OPT