Do we have a member that is knowledgeable about the crank trigger and CDI...? I know RayCour knows quite a bit about this stuff - Richard Avatar has reworked the trigger and ancillary parts...

What anomalies can these parts develope?
What clearances/tweaks can be performed to correct an "anomaly" with any of these components?

Is there a way to gauge ignition performance effectively..?


PWJM does have a Dyno shop relatively close.. I'll check with mine for ability to diagnose such an issue..

 

Snowdrifter, you probalbly alerady know this, a well done MCM starts instantly - absurdly instantly - so that's a good sign that your MCM is correct..

This issue has either gone unreported or is exceedingly rare.. In fact, we need a new term to describe it so it doesn't get lumped in with other known issues - such as the high RPM "missed a stroke" anomaly that we all can get from time to time.. PWJM calls it "stumbling/sputtering" ... Practically unrideable @ 4-5.5k rpm..

 

Agreed, having some common terminology would be a good idea. I was initially quite concerned after doing the MCM that I had somehow messed something up with the cams. But after feeling the difference in how the engine pulls, and then reading about other members who were experiencing the same "flat spot" or "stumbling/sputtering", I was confident that the MCM was correct and the issue is elsewhere. Perhaps myself or another member with the issue can try and record a video. Not sure but it might help to explain (show) others what is happening.

 

Snowdrifter, between your good-to-go carb setup and all the known-working setups we have tried on PWJMs' bike, It can't be caused by needles, main jets, pilot jets, slide springs and such.. One case where the KLX's ability to run fine with all kinds of fueling curves is helpful.. As our recent threads indicate, we have painstakingly measured needles to confirm contours, and listed common mistakes and issues with the CVK.. So far we have found nothing carb related.. His butterfly seal was leaking but was fixed. He has cleaned and cleaned to verify functioning of the primary fueling circuitry...

Could there be some kind of rare issue with the CVK's construction?

Is there some way the "choke" system could be "screwing up" and causing this ? Who understands the choke system well enough to conceive issues that could arise? I know it opens a passageway to the diaphragm "area"..


It would be nice if there was another KLX near you and available for swapping parts..

 

The choke mechanism - with the increase in vacuum that the MCM produces - especially in the 4-5k range - Could the choke "leak" ? If so what would it leak - air or A/F ? What would be the effects on the diaphragm operation? Would a leak cause the slide to close or lower abnormally? In other words, is the port that the choke opens up in the diaphragm area, above or below the actual diaphragm?

I ask because I'm burned out (at THIS moment) and just want quick answers..LOL

 

The enrichment (choke) circuit is one possible culprit. It pulls air from the area under the diaphragm to be mixed with fuel and enters the intake stream after the throttle butterfly IIRC. I remember when I was looking my carb over and inspecting the enrichment plunger, thinking that it didn't seem like it sealed very well in it's respective bore. But I never actually removed it to see where the actual sealing surface was. I can't make a good guess either way without additional disassembly and inspection.

 

m_carb_10.jpg[/IMG]

Are my observations below correct?

It vents to the lower chamber- which is vented to outside air.. So no effect on slide ops, assuming the diaphragm vent is functioning..

Circuit uses carb vacuum to draw additional fuel from (starter jet?) , emulsify it with the air inflow from the port (going to the diaphragm housing), and then the AF is drawn into the carb bore...

So if it doesn't seal off or leaks at some or all of the fuel and/or air ports, you could end up with air, A/F, or just fuel entering the carb..?

 

That might also explain why pulling the "choke" out while in that range has very little effect on the issue.

 

Yes, your logic sounds correct. And looking at the diagram, the fuel sealing surface of the plunger may be at the end, but the outer diameter of the plunger in it's bore is what blocks air flow? It may or may not be normal, but I felt like the plunger in my carb had a slightly sloppy fit. I wasn't too concerned as I thought the end of the plunger was the only sealing surface. Is it feasible to somehow block the entire enrichment circuit from introducing air or fuel into the intake?

 

Is it feasible to somehow block the entire enrichment circuit from introducing air or fuel into the intake?


That was gonna be my next question.. I don't think so..


It would be nice if others could chime in on this.. Especially those that have had the choke system apart...