I am new to the forum and Klxster gave me some great advice just before I purchased a nice 2011 model recently. I had a chance to inspect the bike and I am convinced it is in completely stock condition-no mods whatsoever. It appears to have been maintained very well so I am actually glad to be starting with one in this condition that also runs well.

So, upon his advice, I will do the following mods in order:

1- MCM mod (now that I understand the complete mod/reclocking of the cams position relative to the crankshaft and removal of either the ACR spring or the entire ACR from the exhaust cam). I plan to remove the ACR entirely-may as well just remove the weight and the risk.

2- Lidless airbox and Klxster’s jetting recommedations that go with that. I will probably place a length of UNI foam over the airbox opening just to cut down some noise and to trap some of the dust.

3- A slip-on muffler (probably an FMF Q4 because the Barker just appears too large for my taste). I’m trying to keep it somewhat quiet too. Then, a larger main jet after the slip on, correct?



My goal is to build a bike that has the most low to mid range torque available for the buck. Knowing that, what header pipe would you recommend that is compatible with the Q4 muffler?



I must say thanks to Klxster for the help. I truly respect what he and others provide for the riders on this site so that those of us who don’t know that much (yet) about this model bike can make good decisions and end up with good results. Mike

 

Thank you Oldboy, I suppose we talked on the phone ?

For max TRQ in the low-mid rpm range, the stock header should be retained.

Having said that, there is a new possibility - the Delta TRQ Pipe ( - DELTA - EXHAUST SYSTEM ) ... Before purchasing, the exact diameter of its' bell/slip joint must be determined.. The nipple on the Q4 midpipe is designed to "machine fit" (no gasket,metal to metal) into the stock header bell once the stock exhaust "donut" is removed. It also "machine fits" into the FMF headers (mega and power bombs) .. The best performance slipons will all fit the KLX in that manner.. (But some do not - they have tiny nipples that will only fit the stock header, and require the "donut" to be in place.. See the sticky on exhaust options..)

A question to ask Delta could be " Does the Torque Pipe accept the stock exhaust gasket and stock slipon ?" If it does, then it is carrying a stock dia. bell and will accept any slipon.. Or just ask if it will fit the Q4 without any gasket..

If / when you check the fitment of the Delta, let me know and I will add your knowledge of it to the sticky..

As long as the "airbox foam cover" you are planning does not "materially affect/alter" the air pressure gradients ( ambient vs airbox vs carb bell entrance pressures) , you should be "ok"..

MCM + Lidless setup+ slipon creates a very powerful TRQ monster wheelie machine - as can be seen in my video below..

 

I'll second that. Have learnt heaps from Klxster's input and advice.

 

AussieCheech, be sure to look over and even print out the MCM PDF below, on my signature line,,

 

Hi Klxster-I asked whether Delta's pipe would work with an FMF Q4 and their prompt response is as follows:

"If you are currently use FMF Q4 pipe with stock header pipe and gasket our pipe can be used with your current silencer".

 

Well, that's not an answer - and seemingly shows a lack of knowledge, on their part, about the issue.. When FMF slipons are installed on ANY KLX header, the stock gasket (or any kind of gasket) cannot be used !

IIRC, when they first advertised their pipe, they claimed it produced increased trq through its' longer-than-stock configuration. But I see nothing about that on their site now..

I'll contact them and see if I can get the "low down" on all its' dimensions..

 

I also asked about performance specs but they did not have anything available. They only said that their pipe was larger diameter and it "usually provides better power and response". If the pipe usually provides better power and response, then I wonder where that data came from.

 

There are reviews now, apparently on their KLX pipe. I read them and it would seem the pipe does not provide a focus on low-mid TRQ production. Also, it seems there are issues with clearance with the clutch cable. I assume the reviews I read are for the KLX part number, but cannot be sure every one was...

The step up design that seems to be used (you have to be careful to view only the DL30-2402) does not typically target low-mid trq production.

I'm thinking the stock header is probably still unmatched for low-mid TRQ production..

 

BTW, a thought..
Considering the pieces of the puzzle regarding KLX250S performance. It would seem Kawa designed the airbox to be quite restrictive (due to regulations, no doubt), designed a small dia (high trq) exhaust system, but left the cam timings set for upper RPM power... This is why a well matched performance exhaust header+slipon and lidless airbox/fueling creates "monster" top end power (5+ hp !) but with a weak low-mid. And is the reason that MCM + stock header+Lidless fueling creates so much low-mid power with a trail-off @ 8500 rpm..
We are just plain lucky that the MCM properly recoups low-mid while not significantly affecting top end on our "best overall" recipe of MCM+ complete performance exhaust + Lidless fueling