I really doubt how much you gain from redneck engineering the stock catalyst equipped muffler. Other than an increase in noise. I have done the cam mod and adjusted jetting and it pulls much harder. Prior to cam mod I had done dynojet kit, p-bomb&q4, screen delete, k&n filter and 13t countershaft. It pulled through the rpm's so well after the cam mod I put the 14t back on and it still pulls better than the pre cam mod setup with 13t sprocket. Unless you have done the cam mod and jetted correctly you can't really speak to it's benefit.

 

Have you ever seen a cross section of the stock muffler ? The Cat is not the major restriction. IMO once the stock muffler is unplugged the weak link is the stock header.

 

I've got an old version of Desktop Dyno (computer program)...not perfect, and not real world, but fairly accurate assuming you put in the right info. Anyway, I punched in numbers to get as close as I could to the KLX engine configuration, and the OEM cam profile info. According to Desktop Dyno, moving the cams as suggested results in losses at low and high RPM's and no significant gain in the middle RPMs.

Take that with a grain of salt...like I said, it's not perfect. This engine combination is at the margins of the program's capability to analyze (actually, it's outside of the margins).

It's very possible that narrowing up the LDA as described does fatten up power in the middle of the curve, but personally I won't likely try it until someone demonstrates a quality dyno comparison - the cam mod being the only variable (and assuming proper fuel tuning is done with both cam positions).

 

I think Marcellino has already done this. Has anyone here with a stock bike pulled the lid installed a butt plug in the stock muffler, rejetted and seen 25 HP.

 

I put mine back to stock.

Posted here
https://www.kawasakiforums.com/forum...s-351-a-36022/

David

 

David what jetting changes did you try. On my 250 I had to go up a size. My initial impression was lackluster until I played with jet size. I am not going back to stock it just wouldn't be right as good as it runs now.

 

I would like to do the 351 this winter. So I guess I will have to wait until next spring to know how it will work with my setup. Are the TM carbs really sensitive to main jet size? I recall reading that somewhere. I would like a real carby one day as these CV carbs are soggy. And a pain to tune with pod filters and I would assume with the airbox lid off.

 

I'm really eager to see how this mod pans out. Fortunately I'm broke so I can't rush out and pay somebody to do it (and I have the sense to not try it myself at least without serious help). I'll just sit back and watch and see what happens as others do it, both with and without the big bore kits.

Rob

 

Same header as the D model bikes. They have 32+ hp!

 

When I originally calculated the mod I did not take into consideration that you have so many 350 and 330 in the US . In Europe in general and in Spain in particular 90% + of the bikes are 250 and there are a few 300 here and there .
In none of the enduro forums in Spain there is a user with a 330 or a 350 .
Here are the findings :
Increasing the displacement of the bike in 40% ( from 250 cc to 350 cc ) and mantaining the same intake duct reduces the optimum torque range from the theoretical 8000 RPM of a 250 to 6500 RPM in the 330 and 6250 in the 350 . If the intake cam is advanced in this new situation the cylinder filling at 6000 and higher RPM is sub-optimal ( worsens ) . Also the relatively narrow cam the KLX has needs to close as late as possible in order to somehow fill an allready semi-strangled 350 .
You may do with the exhaust cam as you please , some may like it at 100 some at 110 . Ride the bike in the two configurations and chose whatever feels best for you .
As the original post said this mod was intended for the 250 and maybe the 300 .
I have allready edited the original post : The mod yields the best results for a 250 , moderate results for a 300 and is of little to no benefit to a 330 or a 350 .
Users that have the 330 and the 350 may look somewhere else for more power :
1) For 38 - 40 carbs together with the air intake boot and the front part of the air filter the carbs originally belonged to .( hint ... KXF )
2) Aftermarket higher duration cams .
3) AUS or JP spec ignition
4) reshaping the intake port ( larger ). However this last mod is better left for the shops that have the knoledge and experience to do it , in no way for your average shadetree mechanic .
On the 250 the mod provides better torque and power throughout the range , the mod really shines in the 5000 to the 8000 RPM providing crisp acceleration for the daly rides on the asfalt or on the trail . My bike will get to 80 MPH in a hurry and if I wait a little will go up to 84 - 85 .
I got here by doing a few free mods of my own conception and I plan to keep the bike a 250 , mainly because the gasoline in Europe is like 7 $ / gallon not the 3.75 $ give or take a quarter like in the US .