what is actually going to get the most extra power out of my 09 klx250s, a new carburetor or a full powerbomb fmf pipe? or a diffent pipe? it has 351 big bore and dyno jet kit installed, and some basics like snorkle and smog removed.

thanks!

 

A carb won't get you more power, or at least not much, but will improve response which will feel like power. When you twist, it will go. A silencer would be my next step, and if I had the funds, I'd put a carb before the PB header. On the silencer, how loud/quiet do you want it?

 

thanks! on the silencer i definately wouldn't want it to be any quieter then it is now, but dont want to get pulled over everytime i drive down the street LOL, I do like to make some noise . and i was thinking i would get header and pipe at the same time.

 

It would probably be nearly impossible to go quieter.
I used an HMF pipe for a while and it was obnoxiously loud.
Now use a FMF Q4 quiet core with quiet insert and PB header. Much quieter than the HMF, certainly much louder than the stock sewing machine. My seat of the pants tells me I have less power with the FMF than the loud HMF, but its worth it to me.

 

full exhaust before carb IMO. i really think the stock header sucks, and would ditch it the same time you put a muffler on if you have the funds.

 

haha you're right there IDRIDR. maybe i will go with the q4, i definitely want to make sure i get more noise though.

and for the header do you guys think the megabomb is worth the extra $100 over the powerbomb? or are there other good full systems that are spark arrested. thanks for the help!

 

I think the powercore is also a good option. I just wanted as quiet as I could get with an aftermarket exhaust. The megabomb looks difficult to put a heat shield over. My PB has a shield, installed after burning pants. Muzzy is another option.

 

There is also Bill Blue. He will tell you that he dyno'd his 351 kit with the power bomb and lost hp over the stock header. I don't think he tested a mega bomb - but you should call him before spending mega bomb bucks. Mega bomb type headers do come on new KXF250's so there probably is merit to the idea. If I remember, BB also keeps a dyno chart on his web site for cylinder mod only - something like 22 hp... It looks like adding a carb, slip-on, and airbox lid off gets in the upper 20's when you research this forum.

 

Klxster I recall the thread where there was a 10% loss. I never felt any loss with that header and the big bore since the larger diameter helps upper end performance.

The complete exhaust made a better improvement than the carb. The fcr35 helped throttle response, but didn't really add any more hp. The stock carb rejetted was acceptable if you planned ahead with the clutch.

 

Racegass, Bill told me that the 351 with power bomb lost hp over the stock header and I think I remember him saying it lost 1/2 hp. I don't know anything about a thread talking about a 10% loss. I personally would expect gains with either the power bomb, and especially, the mega bomb. I'm going to have to buy one and do a before and after dyno with my KLX for the forum.
I do agree that Frampton should buy a slip-on as I'm quite sure it will reap the most benefit. If after installing a slip-on, he were to take the airbox lid off and the rejet the carb correctly , the gains should be impressive. It's easy to imagine the lost HP of a 351 exhausting through the stock soda straw exhaust.