Exhaust options for a 06-07 KLX250S:

1) KLX300R OEM header and silencer with all mounting hardware: $483.49.2) FMF3) Fake MegaBomb aka "China Bomb" (Header only)4) Two Brothers Racing5) DG Racing - slip on 2006-2015. (warning this exhaust is extremely loud even with the insert - not recommended for riding anywhere near houses / people)




Thread Index
* Powerbomb vs Megabomb: Headers - FMF Power Bomb vs Mega Bomb - Kawasaki Forums
* Another Powerbomb/Megabomb thread: https://www.kawasakiforums.com/forum...egabomb-35276/


Which is the cheapest option with the most return on the dollar?

 

You don't use a KLX300R header on the KLX250S. You can use a complete KLX300R system on the KLX250S. The components have different dimensions. The KLX300R header has no performance advantage over the KLX250S header - they have the same I.D. !

FMF headers do not mate to stock midpipes or any slipon that has a stock midpipe O.D. ( I.E. the DG's and Delkevics etc).. Chinabomb headers seem to carry the larger O.D. like the FMF's..

FMF slipons mate to the stock 250 header ( once the stock seal in the header "bell" is removed) as well as the FMF headers..

The best bang for the buck is a full FMF system + MCM + lidless CVK setup. The increase in power has to be experienced to be believed. You go from around 16-17hp, at the rear wheel, to 23 !

 

1) If I am using the complete KLX300R system and the header has the same ID as KLX250S, what am I gaining in using the KLX300R header? Wouldn't I just need the silencer from the 300R?

2) Which FMF system and is it going to make enemies of neighbors? I am more than willing to trade some performance for stealth.

3) Can the MCM be done in conjunction with the BB351?

 

Freer flowing muffler. The KLX300 muffler is apparently significantly less restrictive than the 250 and the 300 outlet is bigger when the plug is taken out.

 

Ok, ran across a site that explains what you guys were saying in more detail. The KLX300R header is the same diameter as the KLX250S, except for the last portion by the outlet. The larger header outlet is designed for use with the larger ID silencer on the KLX300R. One must have the KLX300R header in order to use the KLX300R silencer. Because of the outlet size difference, the KLX250R header would be too small (despite the rest of the header having the same ID) to use with the KLX300R silencer. Only 2000-2007 KLX300R header & silencer will fit the KLX250R.

Also, some aftermarket headers designed for the KLX300R have the larger outlet ID like with the KLX300R OEM part. This explains why some aftermarket silencers (such as the Q4) need a spacer to work with the OEM KLX250S header.

I'll update my top post with this info.

 

You are gaining nothing by using a 300 exhaust system over a 250 header + aftermarket slipon - But you're not loosing anything either. BTW, I own both a "12 KLX250S and a '07 KLX300R. Both are modded for max performance with the 300 using the stock exhaust system with butt plug removed - It pulls "power only" wheelies in 1st and 2nd gear..

There is no end to how much performance you can sacrifice for the sake of quietness. The rule is simple - the more quiet, the more power loss or lost. Best you can hope for is to change the tenor of the exhaust note so that thoughtful riding won't upset the "Hood". The Megabomb + FMF Q4 slipon (without any kind of "quiet tip") is mellow, when ridden conservatively, while not sacrificing any performance capability.

Jhoffy22 and David R ran the MCM + 351. So there appears to be no issue with valve to piston clearances and David R confided that he ran his combo to redline quite a bit.. His homegrown "quiet tip" stinger ( a section of 3/4" copper tubing sticking out of the silencer ) as well as the stock snorkel probably didn't help him make a good performance assessment..

 

Anyone know the difference between the 06-07 and 09-15 FMF Q4? Different part numbers and the newer one can be had for about $35 less.

FMF Q4 Silencer (2006-2007) $329
FMF Q4 Silencer (2009-2015) $294

EDIT: This is answered in the top post now!

 

I don't know.
But I bought a gently used FMF Q4 off ebay that was supposedly an '09+ and installed it on my '06. First with the stock header, then adding a PowerBomb later.

 

Interesting. I called FMF a few minutes ago. They weren't very helpful unfortunately. The tech didn't know the difference between FMF part number #042156 (2006) and #042173 (2009-15).

He did mention that the steel used for the MegaBomb is actually thinner than what is used on the 2-stroke Works pipes. That's a little disconcerting, considering the reports of failed welds and of course rust (which is also a problem on the thicker two-stroke pipes).

I wonder if the Chinese MegaBomb is made with thicker steel?

 

I didn't like the megabomb shape and weld failure issue. A heat shield fits nicely on the powerbomb.

YMMV

edit: Are the stock OEM silencer part numbers different between pre- and post- '08?
I picked up the '09+ FMF after at least one other '06/'07 owner verified a fit.