Posts
7916
Joined
3/21/2014
Location
Saratoga Springs, NY
US
Edited Date/Time
8/23/2023 3:57pm
Picked up a 2001 YZ250 with what appears to be very low hrs. The previous owner did mention he had the bike rebuilt but did not appear to know much about anything…. It ran but had the usual gummed up carb from sitting. Figured I would,tear into her to see what I have. I”m trying to figure out if the cylinder has been sleeved, my magnet sticks to the cylinder walls… also wanting to know if this piston is an Oem standard size? Thanks for any input. 
5CU is an OEM mark on that piston.
Cylinder is plated, not sleeved, IMHO.
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Thanks for your opinion YZed250.. I”m just confused as to why my magnet is sticking to the cylinder walls?
Nikasil has a high nickel content which allows the magnet to stick.
Learn something new everyday…. Thanks…
Your cylinder seems OEM as well as piston.
These bike are sensitive regarding top ends with high hours. Ten years ago, I purchased a 08' YZ 250 and top end was beyond imagination ! Surprinsingly, bike was still running.
Have fun, I had great times on this bike.
https://www.vitalmx.com/forums/Race-Shop,42/The-mysterious-piston-eatin…
Note that there is an ink marking on the rear of your cylinder, near the intake. It should be A, B, C, or D. Use the corresponding piston if you are changing it.
Also look closely at the vertical stripe in your cylinder; it looks gouged.
thanks Falcon, that stripe on cylinder cannot be felt with my finger nail… I looked on the cylinder but could see a marking, maybe I need to put glasses on😂
Sweet!
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