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Who has had a cylinder base machined and head work on a 2-stroke

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I'm wondering who has had this done and it's effects on the power of the bike. I understand it helps add low and midrange power. What I'm interested in knowing is how much did it help and does it kill the top end and how does it effect the hard hit of MX style 250

I've sent my cylinder and head from a 97 RM250 in to have the mods done and not knowing what to expect from the bike after the mods has me curious. Btw it was sent to Eric Gorr at forward motion, he's a nice fella to deal with on the phone but I never got too deeply involved in conversation with him figuring his time was valuable. Plus hearing from people who have had the mods done will be great knowledge.

A bit of background is I'm mainly a street rider but hVe always had some kind of off road bike or ATV. My last couple of bikes were a 92 KX250 that was far more bike than I needed most of the time in the areas I trail ride, next was a GasGas EC200 that I wish I never sold but it helped the family out during a time my wife had to quit her job and raise newborn twins for six months due to stupid decisions made by their mother. The little 200 was a nice mannered bike with just enough power without being such a handful like the old KX was.

The bike I'm fixing up or for occasional trail riding and purchased cheap needing a full engine rebuild but the rest of the bike is in pretty good shape.

The 97 RM250 has a PC expansion chamber and wonder how it will perform with the. Cylinder being lowered, I may need to change to a pipe focused on more low/mid to get the most out of the mods.

Thanks for your thoughts in advance


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I had the cylinder base of my old KDX250 milled down, the squish modified and head re-chambered, and extensive port work done.


I used an FMF Fatty pipe, Powercore silencer, and Boyesen Two-Stage Power Reeds.


The end result was an absolute tractor on bottom that would outpull XR400s on hill climbs with ease (that bike would climb a tree if you could hang on), a strong midrange that would hang with 250 MXers of the day, and top-end and over-rev that was about the same as stock. That was the best off-road engine I've ever had.

Edited by Chokey
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