I started the so called "free" mods last night in earnest. Here's what's happening in the ol' garage over the next 72 hours (I have to wait for parts on some of this):

1) Removed the Air Injection System (Air Valve) that directs clean-side air into the exhaust system right at the front of the cylinder head (some call this the smog stuff). This very simple arrangement consists of a vacuum operated valve and a couple of hoses. The air is "injected" into the exhaust via a reed valve. I just removed all the pluming and the valve and then capped the air box hole, carb vacuum port, and the hole at the top of the reed valve chamber. This won't do squat for performance but it will lower exhaust temp significantly which helps keep pipes shiny if nothing else and cleans up the under-tank area.

2) Drilled the crankcase vent hole at the lower front right hand corner of the airbox out to 3/8". Like the KLX300, this system is plugged up and enlarging the hole helps move air out of the crankcase. It also means oil has a clear shot at your airbox if you lay the bike over.

3) Put my 13t counter sprocket on to stay (I'd been going back and forth over the last 3 days as to which I liked better, 13 or 14. No doubt about it - the 13t rocks).

4) Removed the carb to replace the needle (pre-'06 N1TC needle), drill the slide vent with a #32 drill, and replace the main jet with a #122 (for now. Also have a #125 if needed).

5) Removed the air box snorkel pending replacement with the high flow unit Tony discovered.

I should have it all back together by the weekend and will report results then.

 

Todd,

This looks like it is going to be one of your typical KILLER posts that everyone wants to look at and also do to their bike. I know I'm standing by waiting to see what you do and then copy it myself.

Might you add little things, like where you got this, that or the other? I know, it's posted in other spots, but I think this is going to be a big post and we're going to want to keep it where everyone can read it.

And without doubt, you know it as well as I do . . . . . .

 

Thanks Marty and don't worry, pics will follow. I just didn't have time last night to snap any.

 

WOOOOO HOOOO! It's back together and it ROCKS. Now we're cookin' with gas!

Here's what I did this week again:

1) 13t C/S sprocket.
2) Air valve plumbing removed and all holes plugged.
3) Pilot air screw out 2.5 turns.
4) Slide vent hole drilled out to 7/64ths.
5) Swapped in a pre-'06 KLX300 49 state needle (N1TC) with clip in slot 2 down from the top.
6) #122 Main Jet.
7) Air box snorkel replaced with 14073-1577 high flow unit
8) 1/2" hole drilled in the first baffle plate in the muffler.

Now THIS is the way this bike is supposed to run! Night and day difference! YEAAAA HAAAA!

 

Todd,

You rock! This is kind of what I was expecting to hear. Actually, I've been looking forward to this report. Kind of figured this would make all the difference in the world on the bike. Hey, it's not the manufacturers problems, they're just trying to be compliant with the EPA requirements. I think all bikes need a bit of a tweak on the air / fuel ratio to start making power.

Let's see, in summation you increased air flow in, air flow out and made the air / fuel mixture a bit more to the bike's liking. The difference is probably not discernible on a dyno, but with the Mark I, Mod B butt dyno, I'll bet the little burro has really come alive!

Knowing that the pilot jet screw will make a difference on starting, the mod of drilling out the factory seal and then adjusting the pilot jet to about 2.5 turns should have cleaned up the cold natured side of the bike. Has it done that?

The needle will richen the mid range of the fuel flow, I can imagine that it has give a lot of mid-range power back in the bike, especially in the 4000 to 7000 rpm range.

The main jet probably makes the bike really come alive from 6000 to redline.

All that I've read and all that I've felt when riding says that the 'as delivered' gearing is one of the things that has to go. I know that when a vehicle will go faster in a lower gear, then the final drive is a bit too steep. A 13 tooth countersprocket is the way to go. A16tony has gone with a 13 / 45 combo and his report results say that might be the ultimate set up for gearing on this bike.

The slide being drilled out will increase throttle response on those Keihen carbs.

So, with all this done, does the front end get a little light on rapid throttle opening in 1st gear?

Please give me an idea about what has to be removed / plugged on the air valve plumbing.

Finally where did you order yours from?

I would imagine the total cost of parts to be in the under $50 range with shipping?

Sounds like this "Texas Turbo Mod Level I" is the way to go.

Thanks for taking the time to do this so we can all see what this does for our KLX250S models.

More riding impressions and of course, pictures wherever applicable.

Thanks in advance.

 

I will post pictures soon. They're stuck on my laptop at work. I'll point out all the stuff you need to remove the Air Valve pluming (costs a massive $1.99 at Lowes). Removing that is simply to clean up the bike, save a tiny bit of weight, and reduce the head pipe temp to decrease the chance of leaving part of my riding pants on it.

The pilot screw on my bike was set at 1.5 turns out from the factory. I didn't have time to dink with it last night but 2.5 seemed spot on. My bike was never cold blooded to begin with. Full on choke fired the bike up on the first 1/2 rev every time and I could take the choke off after 1-2 min of riding. Now it still needs choke to fire when cold but the choke can be turned off much sooner.

Throttle response is GREATLY improved with these mods. The bike revs like a banshee compared to stock. I'm no wheelie machine but making the front tire lift is possible in 1st-3rd now.

While the bike is better at all RPMs, the big win for me is top end. I don't mean this improved the top end more than the low or mid, rather that it has a top end now. No more watching revs drop off in a losing battle against physics when in 6th gear.

I can't tell you how amazed I was that it cranked just long enough to fill the float bowl and then fired right up the first time and seems to be dialed in spot on from the get go. That doesn't happen to me often.

Other than Lowes, all carb parts came from my dealer. Turns out the total cost from them is about $40 for the needle, collar, circlip, and main jet. Buying the DJ kit would cost more but would also give you more jets for the price. Oh well, live and learn.

 

Todd, your jetted a bit higher than I am, and running a richer needle. Can you do a gas milage report city/hiway soon?

 

Todd are planning on doing the K&N air filter as well. Do you think it might change things up a bit as well ? I hear they flow real well. I am very curious to hear what your fuel MPG is after these mods. Hope to hear soon as i am putting together a shopping list.

 

Scat,

You might want to stay away from the K&N filter on the KLX250. The way they make air flow better is to have less resistance to air flow. That also means that larger pieces of the stuff that you are trying to protect against are allowed to flow into the engine.

Remember, this bike is mostly ridden in dirt! You need a good air filter.

My bikes all have Uni filters in them.

 

Good point, Does the uni filter allow any more flow over stock?