Is there any negatives with using the stock exhaust with the 351. I'm planning on getting mine in April/May. I have read through all of the threads I've started and it does not look like I have asked this question yet.

I'm not trying to make this bike into a race bike or anything like that, so I really don't want to spend any more money then I have to. The only reason for the 351 is so I can maintain speeds easier on the highway which was another thread I had started a few months back.

 

I have recently fitted the Kustom Kraft 330 kit to my bike & the extra amount of gases coming out of the exhaust is very noticeable, so if the stock exhaust restricts the stock engine then the 351 will need a better flow! Even the noise level changed by a about 15%, my nice sounding FMF Q4 went up a decibels or two with the bigger bangs going on in my bigger engine! It sound s great now as the Q4 was always a shade to quiet imho

 

If I recall correctly, from reading here somewhere or on Bill Blue's original website, the 351 can be run with the stock exhaust and just some minor carb rejetting. You just won't get the full effect. Then as you can afford it you can add an exhaust and rejet accordingly to get the full "kick".

 

I don't think you'll hurt the engine by running the stock exhaust, but I wouldn't even run that stock exhaust on the 250. If the issue is money, I'd do the exhaust, airbox, and jetting first, then later go for the big bore. I think you're getting the cart before the horse.

 

There is no issue with money at all. I just can't see spending a ton of money on a five year old bike. I'm just looking for a little more power to get my fat *** moving on the bike.

I included a few pictures of 4 of my 7 cars to show there is no problem with money. The saturn is not mine and I will never own a car if it's not an american V-8. It was to cold to go out to my other garage and get pictures of the other 3.

 

Just un-cork the stock muffler and run it. A better exhaust will always be ... well, better, but the stock header and muffler really aren't all that horrible once you take out the biggest restriction - that is the tiny exhaust outlet.

09 KLX250S Custom Exhaust Sound - Kawasaki D-Tracker - YouTube

 

I am running the stock exhaust, I like it quiet, so I don't have 1.5 HP, I hardly run full throttle anyway.
Although that video looks good with the mod, it sounds louder, how does that compare with the stock or aftermarked cans, does anyone have the sound data?

 

It really didn't seem to be much louder than stock, but much deeper and GREATLY increased exhaust flow.

 

There's a little more to an aftermarket performance exhaust than just the holes present in the system, and a performance exhaust can help a lot more than just wide-open-throttle. Subtle differences in bends, length, inner diameters, etc. can all come together to improve performance throughout the powerband. And as measley as the power is on a stock KLX, most will appreciate a 1.5 hp increase...especially depending on where the exhaust delivers that increase. There's a reason why exhaust mods are one of the number 1 mods performed on just about any internal combustion powered vehicle. It is not a "snake oil" issue.

 

Well, I don't know much about motorcycle exhaust's but in the video I see 3 screws on the end. Is that so the muffler can be rebuilt. I have seen here where people talk about repacking their muffler but I have no idea what that means.