Q: Can an '03 yz450f cylinder be overbored?

5 replies to this topic
  • yamasaki

Posted June 11, 2006 - 04:08 PM


can the sleeve inside a '2003 yz450f cylinder be bored out to accept larger diameter pistons? or do these cylinders have the nikasil stuff on them?

the new top-end i put in on friday failed on me todya. the circlip failed on one side and the wrist pin slid over and dug a nice groove into the cylinder sleeve.

just wondering if i can take it to a local engine shop and have them bore it out and hone it for me so i can just drop a new piston in there.. :applause:

  • FFRacing79

Posted June 11, 2006 - 04:11 PM


It is nicosil. Send it to one of the plating companies and they can repair the damage and replate to original size, or go oversize and replate. Tdub

  • yamasaki

Posted June 12, 2006 - 03:29 AM


cool, thanks.

i've used a company called Millenium Technologies in the past, they do cylinder repairs/exchange and offer a lifetime warranty on their nikasil plating.

guess i'll just call them up today.. :D

mo money! :applause:

thanks for the reply..

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  • fowler175

Posted June 12, 2006 - 04:50 AM


It was cheaper to buy a new cylinder last time I did it, $285ca for a new one, $325-350ca for a replate. Worth checking, a four stroke jug isn't nearly as expensive as a two stroke.

  • Ga426owner

Posted June 12, 2006 - 05:16 AM


I bought a new cylinder and sent it to Langcourt in Alabama - now I have a 472....great work and nice folks to deal with - turn around time is 2-3 weeks

  • yamasaki

Posted June 13, 2006 - 06:48 AM


did some research... you guys were right.. i cant believe how cheap 4stroke cylinders are!

i just bought a brand new Yamaha cylinder for $200 from Yamaha of Troy. nice.


i'm still sour that i screwed up my own motor after doing a top-end rebuild, but i guess in retrospect, things couldve been worse.. now lets see if i can put this topend together the right way. :bonk:

and this time, i'm using the OEM yamaha circlips on the piston, NOT those cheap, paper-clip looking junk ones.

:excuseme: <= OEM circlips

:bonk: <= junky paperclip ones

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