We drill out the enricher jet to about 0.018". I'm guessing stock size is just a bit smaller, maybe 0.016 to 0.017", because very little material is used.

One member a while back did go to 0.18".

 

Ok, so the dieing while coasting thing may not be notable or a symptom of the larger issue..

Neonarc, It is really interesting that that your "standard method of operating" with the choke seems to perfectly mimic the stumbling..

I'd like to ask if a drilled "starter jet" could play a role with the stumbling issue?

 

That's how I understand it.
Our KLX choke plunger is largely on/off setting.
The KLR system is virtually identical on a larger carb. Under stock configuration with the choke lever on the handle bar, it can be partially opened for partial enrichment. The KLX choke lever can be operated similarly, but it just won't stay in place mid-opening. So, a leak at the plunger/jet interface would seem to act as partial enrichment (rich, not lean). But what if there were a leak around the plunger shaft (have you tried the propane/wd40 leak test procedures)?

 

Propane time !! YEAH BABY YEAH!! (AustinPowersInternationalManofMysteryThe SpyWhoShaggedMeGoldmember)

 

Funny that you mention that IDR... KLXster likes to give me a hard time about testing vac leaks like that (lol, as you can see above).

Though I'm not sure how it would be possible to test for such a leak with the carb on the bike - let alone running.
EDIT: Just re-read what you said. I used wd-40 and propane to test for the throttle plate shaft seals, but not the choke. That's worth checking before I remove the carb, for sure. That would constitute a potential air leak, but wouldn't contribute to the enrichment circuit engaging outside of it's normal operation (not that we're sure that's the issue yet anyway).

I think the best bet is going to be removing the carb from the bike today and attempting to seal a hose around the outlet in the mouth of the carb and either blow or suck air through. There shouldn't be any amount of air passing through that passage with the plunger closed. Regardless of the result I'll be taking the plunger out and inspecting it as well.

I'll update you guys here afterwards. Hopefully i can get some decent pictures. Maybe one day someone can donate a bad CVK and we can get cut-away photo's!

 

I have had a similar issue after re-jetting, bike would only rev to 5000rpm and then splutter like it hit the rev limiter. I took the carb out and before taking it apart stuck my finger it and tried moving the slide up. It would slide up a little way and stick. I took the diaphragm out and re installed it carefully this time. Before putting it back I slid the slider open ,this time it moved smoothly. I don't know what caused it to stick. Maybe the spring or the diaphragm, now I always check the slider is not sticking before putting the carb back. Also when replacing the spring holder back in the diaphragm tube make sure that you don't cover the little hole at the bottom of the tube.

 

If one of PWJM or Snowdrifter is willing to pay for shipping (about $10), I will gladly send a used but good working PaRay cdi for you to try.

It is possible that the problem they're experiencing is due to a marginal cdi box. The problem occurs close to max torque rpm, where the voltage pulse needed by the cdi to produce a spark is higher. One could check with a scope that the cdi produces at least 140V pulses about 12us long while the bike is idling, and that the voltage does not sag down when revving up the engine. But without a scope, the simpler way to assess that condition is to try with a known good one.

Btw, our cdi output is a little stronger (>150V), thus you're on the safe side that the pulse has enough energy to initiate a spark (given a good condition coil, which seems to be the case here).

Ray

 

I'm down to try that. I'm going to check the choke plunger first this weekend and if that doesn't reveal anything I'll PM you and we can work out the details.

Pretty much every case involved CDI units seems to be total failure or issues across the entire RPM range. I've never heard of one failing in this way before... let alone on two separate bikes.

Thanks for offering to help us with this! I had no idea that anyone even made aftermarket CDI units for our bikes!!

 

FWIW, since it likely doesn't have any effect in the problem.

I took a look to be sure. The pilot air jet is drilled out, there is no enrichener jet showing anywhere. That is the air inlet for the pilot jet increasing flow for the idle circuit, not the enrichener (choke) circuit.

It should not affect the mid-range based on Mikuni charts showing jetting circuit effects. Pilot (aka idle) circuit only runs up to about 1/8 in full control and still a bit of effect as high as 1/4 throttle.

Again, since the enrichener is upstream from the draw of the intake it should not have any sort of positive pressure trying to blow it open. Fact is the cable operated versions have a spring set up used in the piston cable retainer that would essentially allow the piston to float if there was positive pressure up against it. My 650 has a cable set up like that and I've replaced the cable before.

This is just to clarify those functions. I still defer to what Richard said, block the enrichener inlet with some tape or a tiny dab of silicone seal to test it if you think it could be the culprit. Scotch tape would work well and the sticky glue could be dissolved with some contact cleaner or alcohol to release the tape.

Question, will it flatten out when brought up to the range while sitting still? If so, run it without the air boot on it and see if the slide is smoothly operating. See what's going on if possible. Could also block intake a bit with a hand or some fingers in the carb to richen the mix (blocking air).

Any chance to see if there's another KLX owner near by willing to swap carbs once to see if that is the issue?

 

I'm truly in awe... someone who knows the "black magic" of electronic ignition!

Swapping parts - good.