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Big Bore kits Klx250sf

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First post wondering if some klx 250 guys could give me some advice. I have an 09 klx250sf and i have done done the basic mods to uncork my klx airbox, pipe, and jet kit. after doing so i still want more power. So about the big bore kits if i get a 351 kit will it make a big difference? i don't want to shell out a big chunk of money if its not going to be very noticeable. Also where is a good place to buy one they are hard to find.

Thanks for the help, Ethan

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Stock trim has the KLX250 at somewhere around 17HP. A 351 from Bill Blue will yield in the low- to mid- 20 HP range, if you jet it correctly, opening up the exhaust and intake, too. I felt like I was on a moped on the stock bike, but, with a 331 (I didn't go all the way to 351, in retrospect, I should have), the bike is much, much improved....it was worth every penny. I believe I ended up with a 132 main jet, the stock 35 Pilot is fine, I have a Dynojet kit needle in it, set as per instructions for Stage 2. HMF Quiet core exhaust pipe, snorkle removed. I can now lift the front wheel in any of the first 4 gears if I need to when riding off-road. The engine is still not a high rpm screamer, might as well shift it if you are over 7500 rpms, but, it pulls like a tractor from 3000-7000 rpms. I really enjoy it.

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Thanks alot for the info

How do you get ahold of bill blue he no longer has a website?

He changed his website address a few weeks ago. I THINK it is bandbcyclerestoration.com

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When my KLX was 300cc, I saw a dyno chart that showed 20-something HP with free mods, Dynojet kit, and aftermarket header. I think the BB 351 should yield at least 5 HP. It is a jump of 59cc, 1 point of compression, and I have a 37mm FCR and 101 grind Webcams.

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Thanks everyone i am defiantly getting one before spring. I am pretty mechanically inclined but working on something of this magnitude with my first bike and first large purchase is kinda scary lol. I don't want to have to sell a kidney on the black market to be able to take it to a shop to install either. Valve clearance scares me lol i have had a couple close calls on zero clearance fiat cars in the past.

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I am pretty mechanically inclined but working on something of this magnitude with my first bike and first large purchase is kinda scary .

If you can do a valve check, follow directions, follow directions, and follow directions...oh, and use a torque wrench correctly, you should be fine.

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I went with the Bill Blue 331 kit because I was concerned about heat issues with my Klx300. I do not have a fan to keep things in check. Since I live in Wichita I was able to visit Bill in person. Couldn't be happier in dealing with him and the outcome. Now I am trying to decide if I want to add one of his Mikuni carbs and should I pick the 34mm or step up to a 36mm. Low end pull is more important to me for trail riding in the mountains. Oh well I have the first half of next year to come up with something.

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