david im getting 50-55 mpg with pumper carb - was getting 41 mpg with cvk jetted 40/135

 

I was getting horrible mileage with the CVK too. I was using the stage 2 Dynojet kit.

Another thing to remember, since you're taking this carb apart many times. When you take the cab out and drain the gas remember to retighten the drain screw. I just did it finger tight yesterday and forgot about it. A few miles down the road it vibrated out and I started to irrigate with gas. Not knowing this, I pulled into my friend's driveway and was going to head across his field. I downshifted pretty hard and just when I did that, it died really suddenly and I smelled gas. The first thing through my mind was something went pop in the engine. It wasn't until I turned it over a few times then put it on reserve did I see it pissing out the side of the bowl where the screw used to be. And to top that, my friend wasn't home and my cell phone didn't work. Remember to tighten that screw. A $3 part can leave you out in the middle of nowhere. I bought 2 of them and will carry a spare with me at all times now.

 

Wow that sucks ferdonkey.. I dont take that screw off

I just calculated a tank 58.8 MPG with the tm36 with wheelies, wot, and mostly around town .. better than the 41-42 on cv carb this is weird.. I dont understand why.. may be because it took almost wot on the cv to get to the speeds it only takes 1/3 throttle on the pumper?

 

I would say you are correct tiger. The carb does work better.

My last four tanks of fuel. 62 mpg, 60, 48, 61. I think the one with 48 I had the carb off a couple of times and I always loose some fuel.

Driving to work with the 250 and stock carb I had the throttle pinned in a head wind sometimes even shifting down to 5th. Now with the bigger bore and new carb I am at less than 1/4 throttle headwind and all.

The bike just gets in the groove at 6,000 Rpm and 62 mph. It stays steady there like it was made to run at that speed. LOTS of power on tap if I just twist the throttle. No down shifting and no more winding the **** out of it to get the bike to go. Wheelies in first any time!

David

 

Cool David.. a question about ur carb setup.. Do you get some "bucking" from 1/8 to 1/3 throttle if you are not opening slide quickly.. just coasting without the pumper? Mine lurched forth and bucked forward alot like it was too lean.. until i richened up the idle circut and raised the needle two notches.. also, hows your idle? rough? I am ironing out all the small things with this carb, but I have to agree.. its like the bike was made to have this carb on it

 

I put the carb on stock. Idle was too lean, so I went with the 15 pilot jet. Better, but still a little lean. I also went with the P6 Jet needle. It was too lean and would fall flat on its face when I opened the throttle. SO up to the 17.5 pilot and back to the p8.

With this setup, I could choke the bike, start it, push the choke and drive away with no problems even in sub freezing weather. Too frikin rich, but sure nice when cold.

Now its too rich and jerky, or twitchy. hard to control. More like a switch than throttle. After a couple of mishaps (lifting the front wheel when turning and spinning the tire out from under me) I went back to P6 with 15 pilot. Idle is stable, starts with choke, but full choke for more than a minute will flood the bike out. Runs good small hesitation or surge just off idle until warmed up. Then I saw the fuel mileage and said "Leave it alone" Bike ALWAYS starts, is a little cold blooded but runs fine. I have tons of power and seemed to tame the herkity jerkity throttle just off idle. I may try the 17.5 pilot again, but not till it warms up outside and I have a few hundred more miles on the current set up.

Idle is stable, but hot start I have to turn the throttle just a teeny bit then hit the starter. It will fire right up like that. If I don't turn the throttle just a little bit it does not start well. Idle speed is 1500 usually. I work in a city so after work if the bike is stone cold, I turn the idle speed up a little so I can get through the 5 or 6 stop signs in a row with out stalling it. Choke is off by the first stop sign. Once its warmed up a little, I turn the idle back down at a red light.

David

 

David thanks.. that sums it up pretty well for me. I will tell you my experience.

My 351 dies if you pop open the throttle with any carb if it is idling below 1500. I think its the starter valve when the pressure equalizes,.. and kdx snorkel.. if I block off the snorkel, the prob goes away.

P4 was too lean, P6 is too rich. 17.5 idle jet, too lean at 0-1/4 idle, but best performance.. can punch it and bike does a wheelie from any rpm. 22.5 idle jet, nice smooth non jerky accelleration.. until the p6 nJ and pumper kicks in and it just takes off.. you see sky.. and in 2nd, the front wheel comes up, and by then you are at 40 mph.. I can cruise around town at 1/4 throttle and it feels just like a cv carb with the 22.5 idle jet.. I wanted the bike to act like a cvk aspirated bike at low rpm and low output, but have the brutal accelleration of the pumper carb.. I like the setup now with very rich idle jet and lean main Jet. Starts right up when cold.. choke, 1/8 throttle, turn choke off.. just ride away. when warmed up, just press starter button, 50% of the time no throttle needed, 50% of time just a tiny opening of the slide and it starts.. similar in all aspects to the cvk, except way more power and much better gas mileage.. who would of thought right? So... whats next... CAMS from WEBCAMSHAFTS? We should start a CAM-RING.. a few of us should get together and split the cost of a new set of cams, send them to webcam, install the webcams, then send the core to the next guy, and he gets new cams, and etc, until were left with a spare set of cams that we can hold for the next guy who wants them to send for the core.. Im willing to put up 100$ right now for a set.. any one else want to? (I just cant bear to tear my bike apart and leave it for a week without cams) anyone want to?

 

I'm done. Maybe change the pilot or not, now its just ride the bike and change the oil. Things are working as I expect, I know enough to keep my fingers outa there. 5400 miles on the bike. I change the oil every 1,000 miles. Lets see how long it lasts.

"If it aint broke, keep fixing it till it is."

David

 

I finally installed my TM36-68 on my '06 KLX. I am running a 351, KDX snorkel and some sort of aftermarket filter. I have an FMF Q4 and a Chinese Megabomb knock off header. I am at 150 ft of altitude in Massachusetts. I have not geared down and am running the stock setup where sprockets are concerned.

I got this setup from mustang, who along with mooredan hammered out some of the original TM setup in the iconic thread "Will a Mikuni TM36 fit a KLX250s?..."


Pilot: 17.5 (VM28/486)
Main: 132.5 (N100.604)
Needle jet: 568 series P4
Jet needle: 9EBY01-50 – clipped in 3rd from the top

I am not sure where my air screw is set now, but it seems right. It's hard to keep track of all those turns. I'm still adjusting the accelerator pump but it comes on pretty early. Maybe at 1/8th.

The bike is perfect except it will occasionally surge at very small throttle openings if held there. I think a .9 pilot air jet will fix that, as this is just the range where this occurs. Since I very rarely ride with a tiny throttle opening for any length of time, it doesn't matter much. I'll update after the air jet change. There's also a little popping on decel, but I attribute this, at least in part, to air leaks with the Chinese mega bomb header.

I have to say this setup worked straight out of the box. The change from the 250>351 seems less dramatic to me than the change from the CVK>TM36-68. I've ridden the bike twice off road now.

The change is so dramatic that it changes what is the best line in difficult terrain. You can pull a higher gear and stay in it longer. You can make the front end light and float it over stuff that would have been problematic before. You can choose the "up and over" line that the bike wouldn't have had the power to make before. I have to say, it takes a bit more guts to ride it this way, but it will do it. If you can see the line, the bike will power through. It's also easier to keep the front end out of the valleys in whoops and it will crank through ruts much better. The power is there.

This is not instantly comfortable. At first I thought there was a problem with the setup, but I found it was that I was used to the slow/weak response of the stock carb. It seemed lurchy, but that wasn't the bike, it was me. It does require more finesse or running in a gear that will mute the effect.

It pulls so much stronger on the highway that it's like a different bike. It's not just a different bike it's a better bike. I would recommend these as a baseline setting for those with conditions or a setup like mine. The bike starts perfect, will idle on the kick stand for hours, and runs great. While I mention this, the pumper responds a bit different when starting as winding the throttle squirts fuel. Best to leave the throttle alone and use the choke to start or figure out what works for you. But, opening the throttle wide will not readily clear a rich state as it will in a non-pumper.

Overall, a great upgrade.


Find the jets here.

Pilot jet: http://www.motorcyclecarbs.com/VM28_...T_P2682C28.cfm
Main jet: http://www.motorcyclecarbs.com/MIKUN...__P2306C18.cfm
Needle jet: http://www.motorcyclecarbs.com/Mikun..._P12774C59.cfm
Jet needle: http://www.motorcyclecarbs.com/Mikun...13952C1766.cfm

 

taxonomy, my KLX300 jugged '06 KLX performed best with the .9 air jet. It was very temperature sensitive using the 1.0 jet. My jets are otherwise like yours except for the main jet. My 300 cylinder setup probably causes that because of a 1 point less compression ratio and less displacement...and maybe elevation. This carb has been a very pleasant addition to my bike.