OzVMX Forum

Marque Remarks => Yamaha => Topic started by: oldyzman on February 27, 2009, 02:19:20 pm

Title: yz125c and yz125x interchange internals
Post by: oldyzman on February 27, 2009, 02:19:20 pm

Hello Guys,
Can i fit yz125x internals to yz125c cases including kickstarter and gear shafts crank etc

Title: Re: yz125c and yz125x interchange internals
Post by: DJRacing on February 27, 2009, 03:11:20 pm

Basically Yes.  The main axle gearing is different but I think that is due to changing from a 428 chain on the YZ125C to a 520 chain on the YZ-X.

Title: Re: yz125c and yz125x interchange internals
Post by: oldyzman on February 28, 2009, 12:03:45 pm

Thanks DJ.
Does any one know about the barrel and carby sizes Please...

Title: Re: yz125c and yz125x interchange internals
Post by: Nathan S on February 28, 2009, 11:51:13 pm

C = 30mm carby.
X = 34mm carby.
The next few models all had 32mm carbs which should tell you something....

"Barrel sizes"?
All had 56mm bore, at least until the 1986 S model. Yamaha does over-sized pistons in 0.25mm increments up to +1.00, and Wiseco do +1.50 and +2.00.

The C and X barrels are interchangeable, provided you have the intake boot to match the carby.

The X barrel has a reputation for being very peaky.
I cannot confirm this, 'cause my X has a ported C barrel on it, so I don't know what a standard X is like....
My (standard) C is pretty much as you'd expect from the specs and the era - doughy down low, strong mid range, good-but-not-great top end.

In comparison, a standard D has more everywhere, esp the top end.
FWIW, compared to the C, the modified X has marginally better bottom end powe, HEAPS more midrange, but falls flat on its face in the very top end - it is a much faster and easier to ride bike than the C.