I'm pretty much at sea level. The bike runs like a raped ape and starts instantaneously hot, cold, or whether it has been sitting for weeks. It can be ridden off instantaneously and the choke turned off pretty much right away. The bike idles perfectly too.

 

I'm 800' above.
That's how mine ran before the header. It still runs well, but doesn't have that 'hit' on the bottom that it once had.

 

Yeah the Powerbomb is supposed to increase the mid to upper range HP at the expense of the low end torque. After I put on the Powerbomb, I noticed the increase in HP right away. I honestly did not notice the loss of torque on the low end from riding it. I only noticed it when I tried to loft the front wheel at a slow speed with just the gas and it was less reluctant to come up. This has always been a very dissapointing thing about the KLX; that it is so hard to loft the front without the clutch. Even a bone stock XT225 will loft the front sky high with a flick of the right wrist in first. If I could do it all over again, I would get the Megabomb....it wasn't available when I got my Powerbomb.

 

This makes it sound like I still have a lot to gain doing free mods. I have to research yet the screen removal, slide drilling, and air box lid. I did all these on my KTM with the exception of the screen. As for mufflers, I really like my bottom end torque so I will probably stick with a stock header until I see someone post some direct comparisons. Now I'm curious about mufflers though and what gains can or can't be had there besides 3-4 lbs of obvious weight reduction, without getting obnoxiously loud.

 

Just keep the stock header, you have best bottom end, top end and instantly made half of the money needed to buy a pumper carb.

A quote from someone who has had these bike on dyno more than ANYONE else:
"As a note, I changed the stock header to a Power Bomb header for another run on the dyno, but actually lost 1/10th horsepower."

Peak HP is "top end". So no gains there and even the butt-dyno of people who bought the header tells that bottom end got much worse.

Now, I'm sure the new and improved "mega bomb" is totally different and gives bike gains just like claimed by the company that sells them

--
Mikko

 

Just from reading all the responses here it sounds like it is a waste of money to do too much. So installing a slip-on, rejetting, removing the snorkel, k&n (or other aftermarket) filter should be enough to get extra power and be happy.

 

It probably is a waste because I ordered on earlier this week. I hope the Powerbomb has some benefit to offer.

 

Yeah, this was the thread I was reading, but I also noted that with the aftermarket 34mm pumper carb and a supertrapp muffler the 351 had significantly more over all torque AND horsepower than the stock muffler/carb arrangement. It was 22.24hp 18.69lb/ft vs 26.65hp and 21.11lb/ft. The power was a little less consistent across the rpm range on the modded set-up, but was still over all significantly more. You can see it at Bill's website http://www.bandbcyclerestorations.com/page_2.html

That's like 20% more hp and and 13% more torque (give or take) with the modded carb and super-trapp muffler. Especially in this power range, that's quite a bit. Not sure what bone stock is as a total comparison, but obviously something, either carb or muffler, or both was making some serious positive difference. Would be great if someone was bored enough to do a dyno test with original muffler and stock carb set up.. then mod muffler with header/ w/o header, then just carb mod.... I'm tired just thinking about all the varieties of options. However, if I had to pick one or the other, I'd definitely pick the carb over the header at the moment.

 

I just got back from a good hard ride, and have a bit of an update.

I live 10 minutes from a hare scramble course that's used for a national championship round, and have pretty much unlimited access. I rode it a lot last year, so I know it, and the bike together well.

It's still lean with the 132, and will probably get faster with a 1, or 2 jet size increase. It's 32 (90F) degrees here today, and the bike is running much better. That tells me that I still need more fuel.

The bike is faster. It's quite a bit faster, and has an aggressiveness that it's never had. I travel the dual track into the property a lot, and know it like the back of my hand.
Because of the extra power, it caught me by surprise, and nearly spit me off twice.
It lugs better than it did before. Although the low end torque does not feel stronger, it will tractor out of trouble where it never would before.
There is still a lot of water in the bush, and I had to slow down to go through, or around a few spots, and was able to stay in 3rd, where I would have previously had to gear down to 2nd.

I was skeptical, but now I'm impressed. I don't think low end power is any worse than it ever was with the stock header EXCEPT after I cut the backfire screen out. Then, the low end was nothing short of awesome. However, the midrange, and top end power it has now (not to mention it's new aggressive personality) more than makes up for it. It IS faster. Swapping the old system back on only takes about 30 mins, so I might try that in a few weeks, and do a direct comparison.

BTW, it really does sound good, too.

 

Hey Zomby Woof....thanks for the ride update!

Seems like you're warming up to the PB pipe! Your back to back suggestion with the stocker in a couple of weeks would be an interesting read for sure. I am looking forward to getting my bike all done including the MB pipe.