hi ive had my 21 for harf a year now was inported and had the engine rebuilt and a few other bits done really like it

i de-restricted it and put some tyga cans on it run it in, giving it some for a bit all seemed good, took her out in the sun yesterday thought i would take it and do a plug chop so flat in 6gear up to 115 ish coming of the gas and i could feel it was going to nip up clutch in engine cut out got my dad to pick me up the top pot seized barrel looks ok piston second hand now looks like it got to hot oil feed ok

so here it is what pistons are better honda or wiseco ect, its a road bike with a owner that likes to ride fast and what main jets would you say it needs i think i would like to go bigger and lose a bit of power

and i dont no what pistons are in it no honda marking or any thing i could see

thanks guys and girls

The Honda pistons are superb. I wouldn't use anything else in a road NSR. The only other piston I would use is the ART HRC piston, but that wont work with an otherwise stock motor.

No jetting talk on the open forum. There's a jetting page in the members section however.
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If I have to take the carbs off once more...

ok thanks for that ordered standard honda pistons

i think i found how it happened the bass gasket had gone so would that have been sucking in air ? because the other piston and barrel are fine and thinking about it the seize piston and barrel had a gray like paist on it could of been coolant

grey paste more likely to be vapourised aluminium from the piston...... have a good look

You could have been looking at the greyish creamy gunge you get when water and oil get mixed together.
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Proud Father of , 05 ktm 400exc supermoto 2018 honda crf rx supermoto

Thanks for the replys I think nobby62 is right because the coolant was fine so do you think the bass gasket would of done that then sucking in air and nipped up because the other cylinder is fine

Its impossible to diagnose accurately without seeing the damage... but if air was getting in then you would have been running lean and thus having high temperature and detonation...