Another happy TM36-68 install on stock bore
 

My CV carb was having trouble with the float sticking/flooding so I went ahead and put the 36mm pumper on it

WOW :eek: much better !

Like bolting on a supercharger or something :D

A quick trip up on down the road and there's no flat spots or stuttering etc. I did a WOT plug chop but haven't pulled the plug yet...I think the 130mj may be rich here at 120' ASL but we'll see. It went through the gears nicely but sounded fat

I think the 17.5 pilot jet may be rich because it won't take any choke at all when starting it cold-though 'cold' here in the Philippines is never below 75 deg or so. But otherwise no low speed running problems. I need to double check my idle mix screw setting

Thanks to those here on KF who'd done the 36mm mod and had the jetting sorted out

I have the accelerator pump 'open' adjusting screw just about all the way in, and though the increase in power right off idle is nice and everything, I may take that little spring off the adj screw and use a nut or spacer to allow a little more throttle opening before the accelerator pump kicks in


So, thinking you can never have too much power.. I ahm just happened to notice the TM40-6 pumper carb has the same external dimensions as this 36mm and with a BB 331cc kit due here in 2-3 months the mind starts to wander

The area under the carb flange on the cylinder head is a little thin I think for making that opening very much larger, but when I have it off to add the 331 piston, I could have a local shop lay some weld under there to then allow some porting to take that intake port flange area out to something nearer 40mm

The OE intake manifold will accept a 44mm spigot-I tried it with a piece of plastic plumbing-and I think the OE manifold can be opened up a bit.

If not I'll buy a 40mm spigot to spigot connecting hose when/if I order the bigger carb and bolt the carb on that way with a fabricated intake manifold.


It sounds like too much carb I guess at first though, but the 250 engine isn't objecting to the 36mm :shrug:

If a 40mm pumper carb turns out to be a tad large for the 331 I can 1 or more dividers downstream of the slide to maintain velocity like on this photo of some other carb from the internet


Attachment 9833


Or sell it to someone with a 650cc single etc


Up UP and AWAY

RA, your choke is in a totally different place than mine. In fact the carb looks a lot like the non-pumper Mikuni 36 that I've seen advertised. I know your market availability may be different than the U.S., but could you show a pic of the accelerator pump linkage on that model. Makes me curious.

Right you are, but that's not a pic of my carb; just a pic of a carb off the internet that's had the divider added

I've edited my original post to clear that up


Here's what's on there now

http://static.wixstatic.com/media/ba...0_0.00_jpg_srz

Ah yes...that's more like it.:D

Fiddling with my pull throttle cable today, I tried just about every routing variation but the cable was still was too tight as the bars swung to the left

Turning the throttle housing upside down so the cables exited below the bar though gave me the extra length I needed with some to spare!


The idle speed adjust screw comes very close to the rectifier(?) mounted on the frame. But that white plastic knob pulls right off and still leaves a slotted screw head to allow adjustments with a screw driver

Odd the TM36 comes with that long float bowl drain plug, where the TM40 uses the shorter drain plug... Yet the internal jetting is the same series for both carbs

It would have bend nice if Mikuni would have added a drain screw to the float bowl


;)

Gotta admit that divider concept on a carb like these isn't one I've been familiar with. Seems kind of cross-purpose on a carb they worked so hard on to make a smooth, unobstructed flow, but then I'm no engineer either. On the 40mm carb, I don't know...this is a KLX, not a CRF450R.:D

On the idle knob, what year model KLX do you have? On my '06 the knob has plenty of clearance, and I'd hate to lose it. It's easy to operate even with gloved hands while sitting in the saddle. Have you tried positioning the carb just a tiny bit of rotation in the manifold? Still, if it doesn't touch, it isn't a problem.

Yeah, I miss the float bowl's spigot and drain screw on the stock carb. You can't use the clear tube method of setting/checking the fuel level.

I did the same thing on flipping the throttle housing upside down to achieve more length. I found I like this setup better as the cable(s) seem more protected from crashes and grabby branches. I only use the pull cable on my carb.

That divider looks like a "PowerNow" devise. Scary Fast Power Now Products

I use to make them for the Yamaha TTR-125 years ago. They provided a little bit more torque from idle to half throttle.

I have an '07 D-Tracker/ The white plastic idle k nob clears by maybe 1mm or less.. and I don't think the rectifier bracket can be bent, but I think it'll be okay. I'm not adjusting the idle speed often anyway so if I have to take the white k nob off it's not a big deal

Dividers are being added to the front, rear, and sometimes both sides of the slide one way or the other. Dyno figures usually show a very slight drop in max hp but many riders claim throttle response and mid range are improved. Not everyone feels a gain, but I'd say the majority do.

With the long main jet access plug in the float bowl I'm limited how far I can rotate the carb clockwise to move the idle screw away from the rectifier. For now both have a tiny bit of clearance

40mm is a lot of carb for sure...but so is an 80cc jump in displacement. It's just something for me to think about :D

That power plate looks good, but if you need more power at 1/2 throttle, just WOT.

I wonder how much the accelerator pump is actually contributing vs just getting rid of the CV carb with its inherent lag?

The accel pump spray isn't that intense and as far I know it works only when the throttle position changes rather than a constant stream in between its starting and stopping point.

If so, then once you wick it open to certain point it's all done squirting until you open the throttle more.


In any case I'll take the huge improvement in power :)


After installing the pumper carb the other day, I went out on the hard-packed dirt road nearby to do a quick test...the bike just roared and shot forward in each direction. The next day I came out to a flat in the rear that wouldn't accept any air. Sure enough the valve stem had been slightly torn away from the tube!

There wasn't that much traction to be had on that stretch; maybe the problem was more having slightly low tire pressure already combined with might be an inferior imported tube that allowed the tire to spin on the rim but I've ordered a bead lock just in case I need it.

If you need rim locks...
I put 2 on the rear (@ 180 degrees) so you can balance the tire, if you take it on the road.
I put 2 on the front as the torque on the front is much larger if you hit the brakes than anything the rear will ever see, 2 if you want to balance it for the road.

It's the accelerator pump that your feeling - a hard hit of power anytime you nail the throttle while cruising up to about 3/4 throttle - depending on how you've adjusted the pump. I take it you've never ridden a modern 4 stroke off road bike. BTW, you can now flood your bike during starting with that pumper carb...when you do, every twist makes it worse. You have to just sit there with it wide open for awhile before I'll start.

Thank you for this thread. I'm sure I'm not the only one eager to hear about the performance enhancement that carb offers.

The pump's spray doesn't have to and really shouldn't be intense. It takes very little additional fuel to provide a real improvement in engine response. And in the bigger picture between the OEM CV carb and the pumper, look at the efficient carb throat design of the pumper. And instead of a throttle plate opening on the CV carb, which in turn has to rely on vacuum to pull the slide up, with its inherent friction, the pumper has a direct mechanical link to pull the slide up. Actually it's fairly impressive that they can get a CV carb to work as well as it does, but it still doesn't hold a candle to a well tuned quality pumper.

I did put the 15 pilot jet back in it and it's much crisper now. The 17.5pj sounded a little fat.


I'll have to try some plug chops on a clean plug. I think the 130mj is off a tad one way or the other. There's no missing or sputtering etc at WOT but it doesn't seem to want rev up the limiter cut off.

It seemed to want to rev higher before the carb swap, so maybe up or down a size on the main jet

The old plug was a beautiful tan on the porcelain, but it might be masking the jetting effects with this new carb

Mid range seems excellent and pulls very hard

It was cold starting (+70 deg ambient) without the choke pretty good with the 17.5.. I think I heard some protest from inside the cylinder when I tried to add some choke right after it started.

Tomorrow I'll see how the 15pj does on a cold start.

I worry more about some yahoo walking up and twisting the throttle while it's parked :eek:


Other than this 2009 XR200 I also have here which is still decades old technology being sold here in the Philippines, my last on/off bike was a late 80's XT600

I was busy with cars and road bikes :)

Well, I'll probably go ahead and try the 40mm pumper after I get the 331 kit installed :eek:


Afterall, there are 40mm carb kits for 1200cc street bikes with 300cc/cylinder, and this 250 isn't balking at the 36mm one bit.

I know the larger venturi will require different jetting than what's on my TM36 now (can't recall what's in there right now other than the 15pj, and 130mj)


Anyway, I'm wondering about jetting that bigger carb. Would it be better to start off with the same jetting as what's in the TM36 and make adjustments, or just start with the TM40 standard jetting?

Standard TM40 jetting is near the bottom of this page:

http://www.ebay.com/itm/Mikuni-TM-40...-/151136836676



So if anyone wants to venture a guess...

:D

After waiting out 2 weeks of rain and inclement weather, the skies have cleared so I turned on the petcock/pulled the choke and after giving it a few seconds to fill the carb fuel bowl, the bike started right up nicely on full choke- and settled into a steady idle.

So for me at least the 15pj seems to be the ticket

Doing a WOT plug chop, the insulator on the new plug still looked brand new, so I raised to the mj to 132.5; the bike felt better at WOT and showed a little color. If I remove the oversize float bowl plug, then remove long the idle screw (after measuring how far it sticks out of the carb) I can change main jet by rotating the carb. Much easier than removing the hole dang thing!

So I left it there for now, preferring to spend more time riding it for a few days before trying the 135. - Which is the biggest mj I had sent over here

I'm getting some sort of slight hiccup now and then at low speed steady throttle while cruising, but it's not fouling the plug or causing any probs otherwise. Not worth trying to fix it would seem.



Guess I'll want to order some larger main jets in case the 331 kit wants more fuel, and I can use them with the 40mm pumper I'll be trying

There's so much low end with this 36mm pumper that I don't see 331cc falling on its face with a 40mm - at least not with this 14/47 gearing

:)

Btw, I threaded my throttle cable into the TM36 carb bracket once - the next time I had to take the carb off I drilled the hole in the bracket out a size larger so the threaded cable end would just slip in and out of it and use the two nuts on either side to secure the throttle cable in position

:cool:

Good thread Richard. I linked it up in here: https://www.kawasakiforums.com/forum...q-links-30733/

I had the same problem on my 2007 KLX250 so I ground a little of of two fins on the rectifier.

Attachment 9769

That long drain plug prevents me from rotating the carb to make changes.
It hits the starter on one side and the Kreiger cam chain adjuster on the other side.

http://i292.photobucket.com/albums/m...pse7fae732.jpg


So I ground some of the material of the drain plug to gain a little more clearance
Attachment 9770

I wonder if the shorter drain plug from the TM40 will work properly on the TM36-68?
Has anyone tried the TM40 drain plug?

Doug

Two comments -

The 250 MX bikes use a flat slide FCR 37mm carb - a 40 is too big. It will have probems maintaining intake velocity to draw fuel compared to the smaller 36. You also have to realize that Bill Blue does a 34mm FCR on his 351s that should tell you a lot.

Second comment, you could pull the tensioner, take off the allen nut and jam nut, then slot the thread end of the bolt with a hacksaw. This would allow adjustment and holding the adjuster bolt with a screwdriver, giving clearance on the carb.

Now a question to you TM users, you say there is no float bowl drain?

That isn't too good. I find I had to drain my float bowl to get my 250 to fire up after about two weeks of not riding it (well below freezing and lots of snow and ice). Cranked and cranked... drain float bowl (previous owners stripped the allen head, so it took vise-grips)... bike fired up nearly instantly. Same deal as my 650. Seems the gas in the carb will have evaporation of gasses that are vital to have it fire properly.

I need a float drain, because I may not run the bike for a week or two at a time, especially in the winter months.

turn off the petcock and run the bike dry before you park it ? that's what I do.

My TM36 sat for almost 4 months. Forgot to turn off the petcock and run it dry. After about 3 minutes of cranking, it still started. Couldn't go for more than a couple weeks without draining the stock carb. I did add some stabilizer before it was parked last fall.
Interested to know if that smaller TM40 drain plug works. A bit more room would be nice.

Time for a Custom Kreiger (sp?) CCT, one with a shorter adjuster bolt.

I've ordered some miniature screws with a oring on the back side with the intent of drilling and tapping the long float bowl drain plug so I can get it all out easily

The lack of a float bowl drain is an inconvenience to me because it doesn't allow one to do the clear tube method of fuel level adjustment...but hardly the end of the world. On the need to drain the fuel like some do on the CV carb, this is unnecessary with the Mikuni. It has a pump, so you can just about always get the engine to fire with this carb unless you have moss growing inside the float bowl.:D

As far as wanting to drain the Mikuni float bowl, if you feel the need, why not just use a 17mm wrench to remove that large plug and let it drain on a shop rag?

Mine is a tight fit next to the starter, and I previously I was of course accustomed to draining it into a cup and putting it back into the tank. Odd that the TM40 comes with a shorter drain plug. I wonder if the main jet sits lower on the TM36 requiring the long drain plug?

What a pain. I never do that on any of my bikes, especially since the float needle seized up in a dry carb on my 650. If the float needle works the petcock doesn't have to be closed. If it doesn't, you end up with a puddle on the floor either way. When I turned the gas on with the stuck needle it filled up the carb and the intake. Fortunately the valves sealed perfectly. I sopped up the gas in the intake after cleaning the needle edges and carb body.

But that's beside the point. Just wondered - If I do the carb I'll have to figure out a drain. Gas apparently isn't too good here in Ohio.

Where do you think the pump gets its gas?

After about 2 weeks, the gas I drain out of the float bowl will not light with a match! I tried.

When the gas is drained the bike fires instantly. That tells you it isn't a rich or lean condition - it is junk gas that won't fire.

Maybe a perusal of the Mikuni catalog will reveal a solution.

I've left my bike parked with cv carb with petcock on all through December! It took about 3 minuets of cranking with the choke till she fired, but she fired!

The "junk gas" assessment has some merit, but the bigger problem with the KLX is that it performs poorly in drawing sufficient fuel during the starting process. I think two things contribute to that...the small starter jet and the KACR. Not all KLX's have this problem. I believe the KACR device must be right on the cusp of being too aggressive, thereby bleeding off too much compression for a consistent cold start. If the KACR has small differences in tolerances between bikes, it could explain why some bikes have cold start issues and some don't. Couple that with a fairly small starter jet size, and you have a condition for cold start issues. Most of the times this can be addressed by drilling the starter jet out to about .018". Now, couple, or triple, the KACR influence, small starter jet, and the degradation of fuel in the float bowl, and you have more elements for aggravating cold starting.

Mark, even though the fuel in the float bowl can degrade to some degree, unless it's been there for a very, very long time...much longer than weeks...if you get enough of it into the engine, the engine will almost always light off...of course, barring completely plugged jets and other obvious reasons. When you have a carb that has the ability to mechanically introduce fuel into the combustion process on demand, it can mask other starting issues that some engines have...like the KLX.

Not an elegant solution, but laying the bike down for a moment will drain enough fuel out of the overflow to freshen up the bowl.

That method is also introducing more fuel into the engine by mimicing a flooding condition.

Can anyone give me the length of the OEM throttle pull cable length for a 2007 KLX250S
Or better, the length of the Motion Pro cable that is used with the Mikuni TM36-38 carb installation

Went out for a Sunday ride and the carb is performing excellent !

With 14/48 gearing I can be at 25mph in 6th and it'll accelerate without complaint. Clean and crisp-just like a CV carb

:)

If you would have drained the float bowl it would have fired up like it ran yesterday.

If I cranked the 650 for 3 minutes it would have run out of battery at about 2 minutes.

Tell that to my bike and numerous others who've had the same experience with KLX and XR 650s! They don't spin very fast and as I said, I've actually put a match to two week old gas and it will NOT light in fact it has that "bad gas smell too. That says a lot. Virtually every big bore owner that has complained about starting after sitting for a week or two finds draining the bowl to work.

We also do have the situation here in Ohio that with weather changes the blends can have some effects in the spring and fall, but I don't know how much.

Then there is the fact that by simply draining the float bowl the bike goes from cranking and cranking to nearly instantly firing up. Again, that says a lot.

I know the 250 is a lot more tolerant, I've found it will start after a bit with two-three week old gas in it, but I also know if I drain it the bike fires up instantly. Part of it is that the small engine can spin a lot faster and easier with the starter. I could never crank the 650 nearly as long as I already have the 250, it would (and has) kill the battery.

I dropped the pilot jet to 12.5 from 15; it started and ran better on full partial choke (not locked into position) for a few seconds. It's probably 80F here so not much choke needed in the morning.

It was running fine with the 15pj but when starting it was obvious it was a little rich.

Test ride later

Some day I'll need your recipe for setting up the TM36-68. Thanks for the work and keep it coming.

We're all in this together !