84 atc 250r

[Kazi84R]

Piston siezed in front by exaust. "What would be the reason for this could they have jetted it wrong?" By the time is seen it the whole front was melted on the top side. It was the stock piston but this thing had tons of power no loss what so ever. Compression was 138 before they jetted it. What could have gone wrong after I got it back went for one ride to its death? I will post pics in a few days I have to get it out of there first.

[WilliamJ]

Detonation.

[JasonB]

So I don't fully understand your story, did someone else jet this? Why did they change the jets? New mods? What were you doing when it burned up, long wide open throttle runs or putting around?

I had three 300R kits go on me; I was running massive jets to keep it cool and the bike still kept melting rings. Improper jetting will cause the damage you described. So will getting the motor too hot by running hard wide-open throttle for long periods of time on those air foolers

[Kazi84R]

Well I got a new carb "I had another thread about that" it was a 30mm round slide carb jetting was wrong took it to the honda shop. They jetted it 4 different times and told me 4 times thats the best they can get it. All times it bogged real bad when I tried to start off. After I got it the last time I went around woods one time "it was plowed with bobcat"I took one rip down road hit 4th stoped turned around came back didnt even make it to 4th gear. It was 15 degrese out though >.<

[RIDE-RED 250r]

Melting down the exhaust side of the piston is a classic example of running too lean

[Kazi84R]

Update crank seals where bad wich I guess explains the trouble jetting it So I guess it is what it is. time for the rebuild. Thanks to all that replyed on this and my other thread.