I just bought an '09 KLX (green). Is anyone on the board planning to take their '09 KLX to 331cc? And I'm wondering, for those who have already done the 331cc upgrade, what is the most popular (and best) exhaust option with that mod? Is a full system best, or will a slip-on work just as well?

Ideally, what I'd like to do is choose the aftermarket exhaust first, and rejet the existing (stock) carburetor for that setup. I'll then replace the carb when I do the 331cc upgrade (either later this year, or sometime early next year). But first, I'd like to open things up a bit and get rid of the very restrictive stock exhaust!

Any recommendations on either a slip-on or full exhaust system which would work well with the stock cylinder/stock carb and could then later be reused for the 331cc setup? Ideas and comments welcomed! Thanks!

Jeff

 

I just converted mine to a 300 with wiseco piston in it. For the exhaust I whent with the Fmf power bomb header and the Fmf Q4 pipe. The power bomb headers tubing is much bigger than the stocker. If you go 331 I would dump away all the stock exhaust system for a full exhaust line. Or you wont be able to get all the benefit from your 331. Im still running the stock carb and im very please with the performance.

 

Thanks for the quick feedback! How did you rejet your carb? Has anyone else done anything similar?

Jeff

 

I've got a KLX-300 pipe and muffler set for my upgrade. I'm going to take the Muzzy savings and use it as a down payment on a 331/340 upgrade.

 

how do u like your modified 09? is there a big difference?
who sells the 331/340 kits? and what else do i need to buy to get it all done

also were u able to remove any weight off off the bike? how much .. where?

would love to hear about your experiance.. since i am very close to pulling the trigger on an 09.. but want to know if i can make it lighter and more powerful first?
also can u give me an idea of how much it costs for the upgrade parts and installation... ie ( new exhust, jetting. 331/40 kit.. etc)

Thanx
cheers
AG

 

if you upgrade to a 331 or 340 kit you will immediately lose any and all of your Kawi one year factorywarranty. If I were anyone with a new bike, I'd wait a year because we've already had one '09 tranny go down in flames. A nice exhaust, carb rejet, and airbox opening not to mention the all toocritical 13-tooth front sprocket will suffice most until the warranty is up. But you will be basically forfeiting your warranty if you upgrade the cylinder before your warranty expires.

the 331 kit will require a 300 cylinder to rebore as the 250 jug is not thick enough to take any larger. the 340 kit uses a pressed in liner in the 250 jug which saves you the money on the extra 300 cylinder but you will have down time when the machinist is working on your cylinder.
You should add a FULL exhaust if you upgrade to 300 or above as the oem header isn't really large enough for that much displacement to breathe properly. hope this helps.

 

Thanx you all so much for the input

would upgrading to a 300 also need rebore too? is the a kit that can just be sliped on the 250 without any machining?

also what would the cost be for all this...?
who sells the kits??

cheers
AG

 

yes, the 300 Kawi kit can just be bolted on but you'll still void your warranty. I don't know of anyone who sells this as a "kit". But you can buy the parts for around $450 I'm thinking. You can pay the same for the 340 sleeved kit and get lots more torque. Buying the 300 kit, you'll feel the hit twice if you want to take it any further than 300cc. But hey, I'd rather have 300cc than my 250cc right now.

 

<---- confused as usual.

so the stock jug is too small to do anything with... period. right? so weather its the 300 or the 331/340 you need to buy a klx 300 jug, correct? then have it machined out to whatever size, now do you have to sleve it if your doing the 331/340?

 

331 you need the 300 cylinder.

340 w/sleve you can use the stock 250 cylinder or a 300.