I have a 2002 YZ125 that is in the process of being rebuilt. I bought it and it came with an aftermarket head and lots of other aftermarket parts. I took it to a shop recently and the guy told me that it was a big bore. The stock 125 has a piston that is 54mm in diameter, but mine is 58mm. Basically I'm wondering if i have a 144 on my hands or what?
Question about the size of my YZ125's motor
Started by Robby DiStefano, Feb 07 2012 04:57 PM
8 replies to this topic
Posted 07 February 2012 - 04:57 PM
I have a 2002 YZ125 that is in the process of being rebuilt. I bought it and it came with an aftermarket head and lots of other aftermarket parts. I took it to a shop recently and the guy told me that it was a big bore. The stock 125 has a piston that is 54mm in diameter, but mine is 58mm. Basically I'm wondering if i have a 144 on my hands or what?
Posted 07 February 2012 - 05:53 PM
Robby DiStefano, on 07 February 2012 - 04:57 PM, said:
I have a 2002 YZ125 that is in the process of being rebuilt. I bought it and it came with an aftermarket head and lots of other aftermarket parts. I took it to a shop recently and the guy told me that it was a big bore. The stock 125 has a piston that is 54mm in diameter, but mine is 58mm. Basically I'm wondering if i have a 144 on my hands or what?
Yes the 144 bore is 58mm, piston should be like 57.95 or close to it. The only one I know of off hand that uses a diff size piston is Maxrpm and they use a 56mm piston with a stroker crank to achieve the same displacement.
Posted 07 February 2012 - 06:16 PM
thanks man i appreciate it. I'm stoked. and i only paid a grand for it
Posted 08 February 2012 - 04:43 AM
Sounds like you got a pretty good deal! You'll enjoy it, im sure!!!
Posted 08 February 2012 - 03:05 PM
If the head is aftermarket then it may be athena and most likely have an athena cylinder. If so it will say it right on the side and I believe you will have to use athena pistons. Maxpower does offer a 144 kit with a 57mm wiseco piston and +2mm stroke but any engine builder could build one.
Posted 08 February 2012 - 03:35 PM
I dont remember seeing anything that said athena on the cylinder so I dont think it's one of those
Posted 08 February 2012 - 07:29 PM
My buddy bitches about kids who beat him that he thinks are on "cheater bikes" I looked at his bike in his garage at a party and it says ATHENA on the side. &%$#@! him lol
Posted 09 February 2012 - 04:49 AM
phatheat makes aftermarket heads for the 144 as well. Could just be you stock cylinder with a phat head. Does the head have interchangable inserts?
