I'm sorry to ask questions that probally have been answered on this forum but with limited time to get on line I have to take this short cut. What are big bore kits?How much more power do they give? How much do they cost? My riding partner's bike andmine are the same, 07 klx250s's. They are both stock but we want more alot more power. I'm 6'1 180lbs. my partner is 6'3" 230lbs. What do you guy's think we need to do to these bikes?
We really like the bikes feel and don't really want to trade them in for dr400's. I'm an old 2 stroke enduro rider (late 70's to early 80's yamaha dt175's and dt250's)and expected more out of the klx 4 stroke and didn't expect to have to mod it to be happy with its power. In fact I just sold my 1980 yamaha dt175 which still ran really good. I liked the looks of the klx250s and figured if keep me happy for another 27 yrs LOL. Anyway let me know what my options are to overcome gravity with front tire LOL. Thanks
Also we would like to hook up with other riders, we are in sw mo. near branson mo.

 

Two words for you

Bill Blue

b_jblue@sbcglobal.net

 

Do your self a favor and search the forum. There is alot of info on here about free mods that help alot to gearing changes, exhausts and other power adders before the big bore. Most of the intial mods should be donebefore you big bore to get the full potential out of the big bore(exhaust, jetting, opening the air box.) And yes stock the bike is a slug. Exhaust, opening the air box up, jetting, and a gearing change really wake the bike up at 250cc displacement. A full exhaust will be needed for the bigbore anyway. What type of riding are you doing?

 

Big bore kits are a cylinder that has the bore size altered (enlarged), along with a new piston and rings to match. Matched with the right carburetor or carb setup, the power gains are relative to the increase in displacement. Typical sizes are: (1) Direct bolt-on of the KLX300 cylinder (292cc). (2) 330 or 331 (depending on who's doing the math). (3) 340cc.

You need to have a cylinder to be worked on, yours will work but then you'll have down time while your cylinder is being worked on. Bill Blue does boring/sleeving out to 331 for $430 plus shipping. You can get Nikasil coating (instead of a sleeve) from Kustom Kraft. They warranty their sleeves for 5 years, and their coating for 1 year. The Kustom Kraft big bore kit (330cc) is $769 + shipping, which includes a brand new cylinder. A brand new cylinder for a KLX300 (292cc) is $309 + shipping from www.ronayers.com. You'll also need some gaskets, about $30.

I put the 292cc cylinder on my bike. I'm very pleased with the results. My plan is to send my old cylinder to Bill to be bored out to 331, but that's a project for another day.

Good luck.

 

I'll be 60% street 40% wide varity of offroad.
I'll search the web for a website for Bill Blue.
thanks

 

Bill doesn't have a website except this one and advrider, he's a member who happens to be a machinist.

 

You can contact Bill at b_jblue@sbcglobal.net

 

Aren't we forgetting to mentionthe Thumper Racing 340 big bore kit?

I'm certain that Bill Blue has an awesome kit, but to me the 340 number is synonymous with 70's muscle cars like the 340 Cuda etc. A small block engine that loves to be revved and makes some serious ponies.

 

Yeeeeessssss! 3threeeee4fooooorty! Furtermore, it comes with a Wiiiiiiiseeeeco Piiiiston. Wiseco sounds so much more sexy than J&E!

 

I have the Thumper 340 and its transformed this bike into what I thought it should be from the start!