PWK leaking at air screw

[Bailey28]

I noticed something that never has happened to me before with a Keihin PWK. After riding it a while, I tend to collect a spooge mix of oil and dirt right at the air screw and float bowl area of the carb.

I thought it was the oil in the air box boot coming out, but the clamps are tight and I clean it out often so no oil pools.

I just cleaned the carb, airbox, boot, clamps, hoses and everything after I had it off the bike. I then rode for 15 minutes around the yard and I have the purple oil again. The oil comes out from the air screw!

I looked and some Keihin models have a small o ring behind the air screw spring, however mine does not. Anyone else have this issue? Can you install an O-ring and not screw anything up?

[elemetal]

All the PWK's I've had apart had that o-ring at the air screw. I'd put one in for sure, it'll help with the oil coming out and any dirt/air going in. Pretty tiny o-ring though.

[RBD]

No, not all PWK 38mm or 36 mm carbs use the o-ring/washer sdet-up....

My first encounters with the o-ring in the PWK's were the KTM carbs which most all of them used. The gasgas carbs did use this o-ring/washer up until about now (past year or so) and not all of them did either.

The o-ring is a good idea, but not so adaptable to the carbs that do not use them. The problem is that putting the o-ring/washer in a carb that originally did not come with them (gasgas), the spring will coil-bind before the mixture screw is fully closed, and this will change the known setting you use to use.

To use the o-ring/washer, the spring relief hole would need to be about 1+ mm deeper in depth (NOT recommended).

Most of the time when gas weeps out of the mixture screw threads is when putting it over on the side stand with a hot motor and maybe a leaky float needle, or too high of a float level.

[Bailey28]

Ron, thanks for replying. You did a KDX carb for me several years ago and it turned out awesome!

I lowered the float level after I got my 300 as it was leaking on the sidestand. The bike runs better and does not drip now, even on the sidestand.

Regarding the air screw spring, could I shorten the spring and still have the O ring fit? I have a few o rings that are really tiny that I could get to thread in with no problem.

[RBD]

Your idea in cutting the spring down in length should work fine. When trimming the spring length, make sure it is square and flat and would recommend removing one coil from the spring (I like using the tape sander for this job). Then I would carefully pull the spring apart, stretching it back to the original length.

Once you have the spring trimmed down, put the cut end of the spring up against the threaded head of the mixture screw. Next you need to install the flat washer and then the o-ring, in that order. You need the washer to keep the o-ring from winding into the spring and getting cut or bound.

The o-ring is 5 mm OD and has a 1.2 mm Cross Section

The washer is .5 mm thick and has a 5 mm OD and a 3.15 mm ID

Hope this helped?

[Bailey28]

Thanks, I came back from the hobby shop with some supplies. I used the O ring from my fork bleeders, the Sachs bleeder screws were 3mm, or roughly the same as a #6 machine screw, which is the same as the air screw shank.

Spring sanded down and installed with a flat washer. Thanks!

It's raining here so no test ride yet.

[eff]

You sure it's not chain slop???? I get "stuff" there too and decided it was chain lube being flung off.

[Bailey28]

Yep, I only dry lube the chain with white teflon.. Nothing to collect or fling off.

The Yamalube is purple, so is the residue that weeps from the air screw area. I thought it was coming from the air boot, but that is not the case. It almost appeared as if the float bowl gasket was bad because the oil/fuel residue ran along the seam between the body and the bowl. Most of it collects in the pocket under and next to the air screw.

I can't believe Keihin doesn't install a stupid little washer and o-ring to keep things from gooping up. Whats next, will carbs come without jets or needles?

I will test run after it stops raining.

[GMP]

What do you mean its raining and no test ride?

This isn't baseball.