I have an 86 TRX250R and have to replace the rings after 4 moto's . I have changed the crank to a hot rod , i have bored it 6 times i run stock and wessico pistons and the ring wear happens again . The wear is at the exhaust port side of the piston . Is the porting job bad ? Is the sleeve bad ? I have changed oil mix and oils and nothing seems to help . Anyone have a clue ?

 

do you have the dowels installed on the cylinder studs?

 

yes the dowels are in place.

 

I believe that if your exhaust ports are opened up by removing the "bridge" in the middle, that will cause excessive wear as you described. Also, if your ports are not chamfered that will also cause accellerated ring wear.

 

Here's another angle on ring wear in the exhaust port area: Running lean will greatly accelerate wear in the exhaust port area for the piston and rings. Running REAL lean will cause the piston to melt in this area and leave deposits on the cylinder walls. Many meltdowns happen from lean conditions and this is exactly what shows. You may be jetted correctly but have a seal or gasket leak, causing air or trans fluid to get sucked in. This will make it lean (more air or more oil = less gas = lean).
You can't really jet by the plug nowadays as well as you used to, because of new fuel additives, you just do it the old fashioned way: jet rich 'till it stumbles, then jet down one from there. test at midrange too, so you get a reading on the needle, not just the main jet.
OR, like someone said, you might have badly chamfered ports, but this would have showed up long ago. Is this a newly ported cylinder? if not, that's not it.[img]i/expressions/face-icon-small-confused.gif[/img]

 

Is your exhaust bridge relieved? What oil and mixture are you running?
A picture of your piston would be helpful.
ERIC

 

Your jetting might be OK, but something that most new and sometimes older riders don't do is to warm the engine up for a few min before you open it to full throtle. Running a cold engine will wide open before it is warmed up will cause your rings to wear out early on a 2-stroke and many other parts on a 4-stroke. This might be your problem.[img]i/expressions/face-icon-small-happy.gif[/img]