kx125 stroked to 60mm

[Canmx120]

Hi everyone, I know a guy who stroked his 2003 kx125 to 60mm and was wondering what kind of engine this would produce? He has a spacer plate under the cylinder and has had it on a stand running, so there's enough clearance for everything.
My guess is a slower revving engine with good(for a 125) bottom end but suffering a bit up top.

Also, I've only ever heard of 2mm stroking on a 125, not 2.75, has anyone else stroked their bike this much and had it run ok without engine failure?

I'm kind of eagre to see how it turns out.

 

[hot125mod]

that is 30cc you would need to stroke the crank 6mm there is no way you would have enough space on the crank web to do that and it is unheard of.Remember for every 2mm or .080 you move the crank pin or cut out of the cylindder on a 125 is about 10cc. Have Eric Gorr make it a 154. Thats is as big as I have seen the kawis by having your cylinder cut to a 144 and the crank stroked 2mm port work, open the cases, and you have options with the head as far as race fuel or not. I am actually trying to get a hold of another bike possibly a kawi and do a big bore/ stroker not sure yet though. Oh man that thing on some Ultimate 2 would be a sweet 250f killer even without the oxy fuel it could still get the job done. :)

 

[hot125mod]

When you stroke a crank you remove material from key structural areas. meaning it will wear out faster espicially the bearing on the large end of the rod.

 

[Canmx120]

that is 30cc you would need to stroke the crank 6mm there is no way you would have enough space on the crank web to do that and it is unheard of.Remember for every 2mm or .080 you move the crank pin or cut out of the cylindder on a 125 is about 10cc. Have Eric Gorr make it a 154. Thats is as big as I have seen the kawis by having your cylinder cut to a 144 and the crank stroked 2mm port work, open the cases, and you have options with the head as far as race fuel or not. I am actually trying to get a hold of another bike possibly a kawi and do a big bore/ stroker not sure yet though. Oh man that thing on some Ultimate 2 would be a sweet 250f killer even without the oxy fuel it could still get the job done. :)

It's a 3mm stroke, and the formula for displacement is [Pi X (radius²)] X Stroke then divide by 1000 for cc
The crank pin would be relocated 2.75mm(stock stroke is 54.5mm) making the total stroke increase 5.5mm and the displacement would be brought up to 137.4cc

I'm just curious if stroking without boring and porting will give you any more power.
The reason he didn't send it to Eric or anybody else is because his dad owns a machine shop and did the work for free.

 

[2 strokes for life]

I would send it to eric. I can get my work done really cheap but i think a porting job would be more benificial.

 

[wileyE]

The stroke by itself isn't going to show a whole bunch unless the ports get reworked also. It may run different and give a result that the rider likes but there no real power to be had without reworking the cyl and maybe the pipe. In short, stroking and lifting the cyl make everything fit, but results in wasted degrees of crank rotation as the piston now falls lower than the transfer ports. This is where most the work needs to be done, and how you go about it, and if it's worth the effort depends on the motor.

 

[hot125mod]

yeah wow i was way off i meant to say 3mm so many numbers 6mm? i think i might have been on drugs that day, thanks for the reality check.