Maintenance & Technical > KX250 / KX125
93 KX250 cylinder advice required
Cantab:
I got my bike a few months ago, runs really well but thought I would take the head off and check rings, piston, crank and bore condition before summer.
Piston and crank looks great, but the ring gap is just beyond the service limit so I thought I would get a new set. The cylinder is plated but it turns out the ProX piston is 67.5mm which is the last oversized from ProX. I assume the cylinder must have been re-plated at some stage.
Replacement Oversize ProX rings are not common where I live and have a long delivery time, so the guy at the bike shop recommended that given the condition of the bore (its pretty good but couple of very minor issues) that I should rebore the cylinder and put in a Wiseco 68.5mm piston kit. (also a long delivery time and not stocked in New Zealand)
My question is can you just re-bore a plated cylinder by 1mm? Or does it have to be re-plated or re-sleeved. I am a bit of a novice so I want to understand this properly and get some impartial advice.
MadKaw:
if you bore it, it will have to be3 replated, the boring process will eat the plating. you could bore and sleeve it though, and the sleeves can be bored without plating.
Cantab:
Thanks for that advice, that is what I thought, but the bike shop told me they could just bore it to teh next size piston. I know it is currently plated, so sounds like they should re-sleeve it actually.
CR480R:
--- Quote from: Cantab on November 12, 2007, 09:14:57 PM ---the bike shop told me they could just bore it to teh next size piston...
--- End quote ---
I dont think I would trust them to do the work.... I would send it away to be repaired...
MadKaw:
there are many reputable companies around the country that do great work. do a little searching on the subject. its been discussed many times....good luck, and stay away from that shop you took it to.
MK
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