A clogged or otherwise restricted main air jet (MAJ) would let raw fuel flow through the emulsion tube into the engine. This would cause severe over richness.

If the slide is functioning properly and the MAJ is not clogged, then how could so much fuel get past the large dia. straight section and initial taper of the needle- Oversized needle jet? And what about a malfunctioning choke not sealing and letting fuel enter from its' port?

It would be nice if it's found that a few CVK's are running an oversized needle jet, non-standard emulsion tube, or something else that is easily solvable..

I ran a far larger main jet than the K148 for quite some time with no ill effects on rideability..


Hopefully, the KLX300R carb will allow you to "nail down" this problem..

 

I think you are thinking about this in reverse-- if the main is clogged, no fuel can even get into the emulsion tube-- air however, still could-- resulting in a severe lean condition.

I did think about the choke not closing all the way when I was fiddling with it yesterday. Its a valid possibility. Its definitely something I will check next time I pull the sucker off.

 

The MAJ supplies a metered airflow to the emulsion tube. If it is clogged, there is no "emulsion" taking place in the emulsion tube - you get raw fuel coming up into the engine instead of Air/Fuel..
Both are brass inserts and the actual orifices are tiny.

 

The only way I know of to verify airflow to the emulsion tube is to remove the emulsion tube and spray cleaner under pressure into the port at the bell and see it come out in the "emulsion tube support casting"..

The same should be done for the pilot system - spraying into the PAJ port and verifying flow into the pilot jet support casting..


BTW, the orifice sizes on both are suppose to create a 1 psi difference between the air pressure entering the emulsion tube/pilot jet, and the ambient(outside) air pressure of the pocket of air that resides above the fuel in the fuel bowl. So blocking of the fuel bowl vent is also detrimental to performance..

 

Gotcha...I thought you were talking about the main fuel jet being clogged. Ill have to spray some carb cleaner in the PAJ and MAJ holes as well.

Thanks

 

Just tried a quick run with NO air filter-- STILL get the sputter-- but MAN when it gets out of the sputter all hell breaks loose! It can carry the power even with the choke on. Its like a lightswitch though-- 4K bog, bog, bog - 6K BAM--rocket like power.

Next stop, pull the carb... Again...

 

Got the KLX 300 carb in, it looks immaculate. Apparently the top and bottom were polished and the rest of the carb is ultra clean. Its much prettier than the carb in my bike. Dont know how it works yet though.

Few quick specs - came with 35 pilot and K122 main (I think its a Keihin anyway). Swapped the main to a K148. I heard some jingling in the cap, so I opened it up-- apparently the guy who last fiddled with it really didnt know what he was doing-- the needle w/clip was resting ON TOP of the plastic retainer WITH the clip in the 3rd notch from top. This effectively allowed the needle to come completely out of the needle jet when the diaphragm is fully raised.

I moved the clip to 2N put the brass washer on top of the clip, set the needle in the slide and then placed the plastic retainer and spring and buttoned it up. Looking at the throttle plate, I can see the screws have been taken out before, but I wonder why?

Last, the needle itself-- its not an N1TC-- I dont really know what it is... A dynojet needle maybe?? Check the pictures below, maybe someone will recognize it. It has a more agressive taper and a more rounded tip than the N1TC or stock needles.

 

That's the DN0352. The needle that comes with the DJ2206 kit for the KLX300. Which means you also probably have a drilled slide and a DJ main jet. That needle looks pretty dirty..

You should be able to "mix and match" the carb parts to determine what is malfunctioning..? Once that is done and your K148/N1TC@1N is back to good working order, we can put together a plan for testing that 352 needle..



A pic of mine (when new) for you to comfirm:

 

The only reason I know of to remove the butterfly valve bolts would be to replace a leaky shaft seal.

 

It does have the drilled slide-- I had the guy confirm before I bought the carb-- I'd rather it didnt, but now that I know thats not the cause of my problem on the other carb, its not a big deal.

The needle is not dirty, on the contrary EVERYTHING in this carb is super clean-- to the point where it doesnt look like it spent much time in the bike, at all. The yellow color you see is from an incandescent light behind me when I took this pic in my kitchen. As you can see in the new pic, the yellowness "moved" due to the different angle I took the pic from. See new pic.

My plan is to try this new needle first, so if you have a recommendation on notch setting at ~35 ASL, let me know.