50's brotherhood mag-unlock the box

[sean01]

hey, did anyone take any notice of the write up that urban motos did on the yx150 engine?
well it applies to all engines i recon..
it does make a bit of sense in the fact that these engines are all over the place in the way of performance...

hmmm, i got a bog stock yx150 in the shed that was a bit lazy on the throttle....time to rip the head off and measure it up and CC the head and piston and see what comp it has.

 

[user 12599]

yer... there was a story on here quit awhile ago were a kid brought a 125cc pit bike, cause he wanted to bore it out or something when he pulled the barrol off that was MARKED 124cc it measured up to a 110cc and for some reason because of that he couldn't do what he wanted to, the thread should be on here some where............

 

[sean01]

yeah some 125 engines came out advertising that they were 125cc but in fact only 114cc or something...
i think it was 54stroke x 52 piston = 114cc.. or was it 52 x 52 =110 and 52 x 54 = 119cc...arrr so long ago cant remember..

just like the 138cc

easy fix tho...change the barrel.

but the article is referring to piston height in the bore not size of the bore...which effects compression ratio... which is where most of your power is generated...

 

[wogtaz ryder]

looks like a great easy thing to do.

what would be better , shaving the head or the cylinder? would it make different effects?

 

[sean01]

should be same effect but doing the cylinder is easier as it can be done in a lathe, some heads are hard to clamp down into a machine...