As I'm starting to ponder and grow with the KLX. I'm getting the itch for more power. The 250 class is okay, but I'm looking into a more fun factor like the KK 331 or the B&B 350. But one thing that has bugged me for a while, what exactly are the piston weights for these kits compared to the stock 250 piston and Kawi's 300 piston? I'm looking into big boreing up, but don't want any high vibrations that may come with it.

 

The 351 don't weigh crap .... just get it, the klx does not noticibly vibrate more with it. Well I noticed nuthin.....but my other bike is a ktm adventure with annnNNNn Lc4.

Just jokin, don't worry about it.

 

Nice to get some weights on the kits available. What do we have?
Stock Kawa' 300 kit. (Kawa' piston.)
BB 300 kit. (kawa' or Wiseco piston.)
BB 331 kit. (Je piston.)
BB 340 kit. (JE piston.)
BB 351 kit. (JE piston.)
KK 330 kit. (JE Piston.)

 

Okay, one piston is xy grams, and another is yz grams... ummm.. so what? There is a reason these are called thumpers

 

more weight in the piston = more vibrations. there called thumpers because of the exhaust sound( thump thump thump) also so much power out of one cylinder. (i think)

 

Nah, multi cylinders generally create more power for the same cc.
Lots of little pushes is better than 1 big one.

What a single cylider offers is simple and light.
Aprillia make a V-twin enduro 450 and 550.

From what I have read, amazing power but a bit too heavy.

But in the future?

 

Does the 331 rev higher than the 351? I'd sure like to see some dyno charts comparing those two. I'd probably still go with the 351 as I'm more interested in torque than horsepower.

 

I posted recently about having ridden a demo bike with the 351 kit installed. I noticed little if any additional vibration over a stock bike.

Norm

 

Vibration is caused by something being out of balance. A lighter piston could set up this situation just as easily as a heavier piston. A few grams of piston weight isn't going to make much difference unless you bother to get the whole bottom end balanced. ! I've a 340 kit and noticed no extra vibrations. Bill Blue is the one to really answer this.

~Steve

 

I should have also mentioned this, but I would also like to know the bore x stroke specs. I can easily find the stock 250 or 300 specs. But what about the 331 and 351. I want to try to square the bore vs stroke, and keep the piston weight close to stock so a rebalance is not needed.

edit:
Okay, forget the keeping the bore vs. stroke square. In stock 250, the bore is 72mm and stroke is 61.2mm. And with the 300, its 78mm bore and 61.2mm stroke. I'm going to do more research and e-mail B&B &/or KK.