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Fcr35?

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I just chatted to a UK supplier of Keihin carbs and they recommend the FCR35 for the DRZ. This seemed to me, on first evaluation, to be a dumb idea as it's narrower than the stock S carb. But he told me that, because the BSR36 CV carb has a butterfly assembly crossing the inlet, a wider bore is needed. The FCR has a flatslide, leaving just a needle in the airflow so a slightly narrower bore diameter can be used.

I know that the throttle bodies on my Aprilia RSV were swapped on the newer models for real wide ones and the bike is now more powerful but it's all at the top end of the rev range. The guy I spoke to told me that the 35mm carbs give more power but in the middle of the rev range and that's why he says they recommend it. In fact, he thought it was a shame that Suzuki fit the FCR39 to the E because they could've delivered a more useable power band with the 35.

I'm just reporting what I was told here so don't shoot the messanger 😢. I'm just raising it for those in the know to add comments and discussion. 😢

Cheers

Ian

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No, that's the whole point of the thread - definitely 35. We had a long conversation about the FCR35 versus the FCR39 and he reckoned that bigger wasn't necessarily better.

Ian

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They are top blokes and know their stuff

PS I told them you would be ringing, and NOT to let you have a carb as big as mine 😢

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All the logic is correct. However you will have a hard time selling that idea here, there is so much history with the 39. Theories are good but simebody needs to try it to prove the ideas and how they work in this particular application. If you are looking for throttle responce and mid range, give it a go. An example I can think of is KDX200 uses 36mm. KDX220 uses 34mm. The 220 is designed to be torque-er (sp?) than the 200. A friend of mine is known to put on a smaller carb on his dirt bikes to improve torque. He does not care about top end.

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While I was on the phone, I asked for the price on the FCR. 320GBP!!!! There's about 1.8 dollars to the pound so that's about $580! 😢

I guess that'll have to wait!

Ian

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I know I'm lucky as all get out with both of my bikes. I cannot believe have clean and crisp they deliver. That's the main reason I've never put a pipe on my 01 E. It's so darn perfect now I hate to mess with it. Plus the stock pipe isn't hat bad of a pipe. Riding in rocks like I do it makes a lot of sence. But the Yosh on the 03 has me second guessing myself now. I hate the jetting game but it would no doubt be woth it once dialed. man that's one strong motor but it's a 440 too. I'll get it figured out before springtime. prairiedawg 😢😢😢

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