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About those 250cc big bore kits

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So what are they doing? On a 150 will they use a 230 cylinder bored, and then stroke the crank? Or are they boring the 150 cylinder out to 175cc and stroking the crank?

How are guys like CoeShow building such big engines - it would seem that if the 230 cylinder fit the 150 cases that would be a good start - clue me in. I'm a techno junky and love to know all this stuff.

Mikeee

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I'm the same as you. I like to learn how these things work and how you make these engine perform. I would like to know if it is possible to take a 230 bottom end, but in Coeshow's mega kick start gears, then do his 251cc bore? So you would end up with a kick-start 251cc engine with a 6 speed transmission.

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I'll give you guys a few pointers........

To build your 150 into a 250 you will need to purchase all of the 230's lower end parts (crank, t-chain, t-chain guides, cylinder, etc.)

The 230 6 speed will not work with a kick start. Kick start gears use up space in the available area needed for the transmission. The 150's have 5 speeds + kickstart, which employs the same area as a 230 engines 6 speeds.

If you want a 6 speed AND kickstart in your 150 or 230, you will need to install a complete XR200 transmission. Personally, I wouldn't do it. There are a few who felt the need and have performed an XR200 6 speed transplant. A built 230 engine will over stress the XR tranny IMO and it will fail.

The XR200 when apart looks almost like a 7 speed because it has 6 speeds AND kick start gears. The difference is that the gears are MUCH narrower to allow them to fit in the same usable space.

This is the very reason 230's are e-start only. Honda engineers, after much analysis learned that the added torque of the much longer stroke engine would necessitate a stronger transmission. The XR200's are known to have problems, especially after major engine modifications, so with the increased power and torque, Honda went with wider transmission gears. With wider gears and 6 speeds, there is no room for kick start gears, plain and simple.

Good luck and ride safely.

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Thanks Mike - I was wondering about this. It seems like the guys with the 06 CRF150 really have it made as far as bolting on big bore kits that are out to what... 225cc? Nice!

I dig your 188cc kit - I think your dyno made as much as the 225 EO kit... gotta be the cam too - or the actual "parts as a whole" that make it run so strong.

Mike

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