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

WOW much better !

Like bolting on a supercharger or something

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





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

 

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

 

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 **** 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.

On the idle ****, what year model KLX do you have? On my '06 the **** 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 *** 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 *** 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

 

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.