Piston Question for 91 CR250

[mifun3]

Hi Guys,

I want to replace the piston in a bike I just purchased.

The current piston is a 67.5 mm

My question is if the piston is 67.5mm, does it mean the cyl has been resleeved cause according to the Wiseco web site (Chart below)
It says that the bike has a Nikasil bore?????

Piston and cylinder are nice and clean but would rather replace now then end up having a piston skirt crack in middle of summer.

If cyl is equal (not deformed) should I just order a 67.5 piston?

Thanks,

Mike

CR250
Pro-Lite
*Nikasil Bore - Cylinder sleeving or
replating required for oversizes
1986-96
66.4x72
249
66.4 - STD
66.75- 0.35
67 - 0.60
67.25 - 0.85
67.5 - 1.10
68 - 1.60
68.25 - 2.10

 

[rm_racer]

If the coating/cylinder is not worn, and you are not going with any larger of a bore, then there is no reason to recoat the cylinder. Just pop a new top end in and go.

 

[mifun3]

Is it possible that someone could have bored a nickel coated cyl without replating it. If so would it last??? To be honest the cyl is clean but just doesn't have a nickel look. I really think some bored it. Haven't had a chance to get the cyl mesured with a dial idicator to ensure it's truly round if it is, I;m probably going to slap a new piston in and keep an eye though intake or exhaust over the summer.

Any suggestions or bewares??? hehe

Mike

 

[TimberPig]

Yes it is possible some clueless individual bored a Nikasil cylinder without plating it, but no it will not last. If you suspect it has been sleeved, look at the base of the cylinder. The dark grey of an iron liner should be readily evident compared to the light coloured aluminum. Also a magnet will stick to an iron liner.

If you are unsure, any decent bike shop should be able to help you get the correct parts, and set them up to last, even if you are doing the assembly yourself.