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Dirt Bike Discussions By Brand
Honda MX & Off-Road Dirt Bikes
39mm FCR on XR400 ?
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[QUOTE="ochster, post: 302874, member: 17624"] IMHO, there is no problem making the oem 30mm Keihin perform decent with just a typical 77 or 78mm 10:5 to 11:1 piston. I also believe this to be the most durable, best bang for money-less headaches mod you can do to these bikes. When building engines with different cams and compression, I have fitted 36mm Mik pumpers, with nice performance gains. I am now in the process of building a engine that will be set up with a 35mm FCR, I havn't yet put one a 250/280. When taking this mod on, one needs to be aware it will involve a susbstantial amount of patience and mechanical skills. Everything from throttle assy's, airbox modifications, jetting, cable routing, etc, will need to be fitted and ironed out. IMHO, if you are not up for this, you are best to save your money for other things. Jetting specs are commonly available for the average/normal piston kit's with the oem carb., and is still very user friendly. I know there are lot's of "flat slide-non pumper" carbs in use. But if I'm going to go through the energy of fitment and jetting, etc., I prefer the pumper. [/QUOTE]
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Dirt Bike Discussions By Brand
Honda MX & Off-Road Dirt Bikes
39mm FCR on XR400 ?
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