Evening all.

I'm doing a top end rebuild on my to-be next race bike, and was fully expecting not to have to change the pistons. Before the rebuild the engine was running fine with no problems, everything hunky dory, 7361km on the Odometer (if you believe it).
Barrels look good and have that cross-hatched honing on them except near one or two of the ports where it is smooth. Everything came apart easily, piston pins just slid out by pressing with my fingers with some effort. Top piston has light streaking, but bottom piston has one area of slightly deeper streaking with the occasional tiny pit. But the thing that really bothers me is this distinct smear that the bottom piston has. I'm new to two-strokes, so I don't know what to expect; what's the verdict on this piston then? As I'm going to scream the guts out of this engine at the track, I think I'll probably have to go for the new piston. Does it make sense to replace both at the same time? Can I get away with using this piston again?




Bottom piston streaking, pitting, and smear:


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MC28 SE -sold-
MC21 with RS250 engine -for sale-
MC21 race bike -soon for sale-

Any damage on a piston is bad... I'd replace it!
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Andy.
NSR-WORLD.COM

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Thanks Andy, I more or less realised that there would be no other answer
Still, I'll take any opportunity to air my dirty pistons in public
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MC28 SE -sold-
MC21 with RS250 engine -for sale-
MC21 race bike -soon for sale-

Your "smearing" is commonly known as a seizure!!!!!
Sort the problem of WHY it happened before you put new pistons in otherwise you will get the "smearing" again and possibly "heavy smearing" in your underpants when the light becomes heavy at the track flat in top.
Have a look at http://www.apexleisure.co.uk/pistondiagnosis.htm
Good luck!!

That'll be mild blow by on both pistons and an intake-side seizure on the front. So the presvious owner ran out of oil, and they were due for new rings ... nothing for me to worry about, except to get new pistons.

Brilliant link, thanks!
_________________
MC28 SE -sold-
MC21 with RS250 engine -for sale-
MC21 race bike -soon for sale-

[quote="iom"]Your "smearing" is commonly known as a seizure!!!!!
quote]

Byatch !


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