fordfather

Member
Mar 5, 2006
5
0
bought 91 rm250 rode 3 times died pulled apart found this

-piston ring land on exhaust side bent and broke apart
-cylinder head has chunks taken out from piston parts
-cylinder sleeve has crack 1/4 long in the center of the 2 exhaust ports. ya know from the left port to the right port

Im new to dirt bikes. I think i need a piston and head maybe sleeve. Could i get away with no sleeve it would cost the most of all parts. also friend says only run oem piston for reliabilty he says no wiesco or namura there light and will quickly need replacement any help is valuable to me thanx
 

TimberPig

Member
Jan 19, 2006
859
1
That cylinder came stock with Nikasil plating, not a steel sleeve, so if it is still stock, then welding and replating will be the better option to repair it. If it has been sleeved, then having it replaced will be necessary. You may also be able to finda used cylinder for cheap if you look around online parts sites, and auction sites.

As to the piston, Wiseco pistons are forged, and are actually much tougher than cast stock pistons, but they expand slightly more than do cast pistons, so they need to be warmed up thoroughly before being run hard. Use what you like, but anything properly cared for and installed to correct tolerances for that piston will last, provided there are no other issues present.
 

fordfather

Member
Mar 5, 2006
5
0
thanx the magnet stuck so do u think i need a new sleeve?
the only thimng i see wrong is a 1/4 inch long crack in between the 2 exhaust ports
 

RM_guy

Moderator
Damn Yankees
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Nov 21, 2000
6,953
182
North East USA
I'd put in a new sleeve. The crack is probably why the rings and pistion blew apart. The bridge expands when it gets hot and the crack allowed it to expand further than usual and the edge of the crack caught the ring.
 

TimberPig

Member
Jan 19, 2006
859
1
fordfather said:
yeah i looked and the sleeve is all tore up
Can i install the new swleeve myself?
LA sleeve wants $250.

Are you a machinist with all the proper tools to remove the old sleeve and install the new one, properly align it, and clean up the porting and all the other fine details needed to properly install a sleeve in your cylinder?

If yes, then go right ahead.

Since you are asking, I am assuming you aren't in the position of having all those skills and experience required to replace the sleeve, and in that case, no. You will be far better off to pay someone who knows what they are doing to install your sleeve for you, rather than destroying your cylinder.
 
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