Two Stroke Motocross
Two Stroke Motocross Forum => General Two Stroke Talk => Topic started by: motoman356 on February 21, 2013, 11:18:13 PM
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hey im picking up another 125 soon and i def plan to mod the motor. so heres the big question. should i send it to eric gore for just a bore or have it bored and stroked to 144 using a 2mm piston and a 3mm longer rod. anyone with experience with these motors?
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You know I have a 04 cr125 2mm stroker crank 1mm up 1mm down, and a 2mm over borre that I didn,t want. With the stroker crank, it comes on the pipe slower. But when it starts pulling there,s a big torque boost over a wide spread, with 2k more over rev. I prefer a standard borre 54mm, because of the weight of the 56mm GP piston, it makes the bike feel heavier. But the extra hp and torque is awesome, 20 lb plus torque, 40 + hp. Pc pipe and pc regular silencer, will try a pc shorty to get it quicker and less backpressure= heat, vforce gonna install a rad valve to get quicker off corners, older model icat, carb borred to 40mm, leaded race fuel. I,m trying to make it quicker, so I have an advantage against 450,s in the tight technical stuff. Ps stroker cranks have a different sound to them, kind of like a whirling sound. When ya fire it up, some riders know right away, they say ah ya got it stroked then there,s talk look out for the stroked cr125. I think everybody knows a stroked 125 , is sick they sound different when on the pipe pulling. Real barky and torqey sounden, but still revs higher than a 125.
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thats kind of what im looking to get out of it.
on another note ive heard if you go to an 05 air box cut a few holes and get the cycra airflow fender you can get the bike to breath better
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You know I have a 04 cr125 2mm stroker crank 1mm up 1mm down, and a 2mm over borre that I didn,t want. With the stroker crank, it comes on the pipe slower. But when it starts pulling there,s a big torque boost over a wide spread, with 2k more over rev. I prefer a standard borre 54mm, because of the weight of the 56mm GP piston, it makes the bike feel heavier. But the extra hp and torque is awesome, 20 lb plus torque, 40 + hp. Pc pipe and pc regular silencer, will try a pc shorty to get it quicker and less backpressure= heat, vforce gonna install a rad valve to get quicker off corners, older model icat, carb borred to 40mm, leaded race fuel. I,m trying to make it quicker, so I have an advantage against 450,s in the tight technical stuff. Ps stroker cranks have a different sound to them, kind of like a whirling sound. When ya fire it up, some riders know right away, they say ah ya got it stroked then there,s talk look out for the stroked cr125. I think everybody knows a stroked 125 , is sick they sound different when on the pipe pulling. Real barky and torqey sounden, but still revs higher than a 125.
40HP CR 
.The over rev and sound come from the longer rod, I assume you went up in rod length?
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Yeah 2mm stroker crank JM racing calls it , 1mm up and 1mm down. 1mm is machined out of the head, very little porting the exhaust port is widened, cylinder is decked quite a bit. Because the transfer ports where way too high. It has a violent and sharp hit when coming on the pipe, the 500,s I rode didn,t hit as hard and sharp. It,s very fun and exciting to ride, it runs like a transformer flip the swith and bam 20 + lbs of torque instantly.
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stroking the crank makes the port timing even more radical, thus the need for long rods or cyl decking or both.
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I built a stroker YZ144 last winter and put it on the dyno and track against a big bore YZ144 from Eric Gorr. Simply put, the stroker makes more power everywhere. It will pull taller gearing easily and still feel stronger in the bottom end, and pull farther. With 14/48 gearing it almost feels like a 250 coming out of corners, and revs like a tiddler.
The price difference between the two isn't proportional to the performance gain, but if you're aiming for no-compromise performance, definitely go stroker.
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if your not racing, do both
that'll be a homebuilt ktm200