2001 KDX 200 breaks up at higher RPMS

[canyncarvr]

It's got nothing to do with wise, that's for sure, but I can tell you it's so. I don't know if it's attributable to incomplete combustion or what. My bike blew spew all over the place AND lean-roll seized (I said that already). And I'm not talking about a 50 pilot with a 138 main running around at 1/4 throttle, either.

Where am I? Out riding, natch! Well, was then anyway.

The point is, don't jet by spooge. There are a number of reasons you'll get spew out the pipe that have nothing to do with whether or not you're jetted correctly. The way to properly determine a main jet selection is by reading the mixture ring at the base of the insulator after a properly run WOT plug chop. Some jet from the bottom (pilot) up, some from the main down. Whatever your method you will likely be doing it more than once to balance the carb correctly. While an incorrect pilot choice won't make a whole lot of difference at WOT, an incorrect main WILL change everything clear down to the bottom. Today, a main change from 152 to 155 pretty much wiped out the bottom end of my bike for example. Off-idle to 1/4 throttle dropped off severely with the single up-step in main.

I changed it back pretty quick!

I still want to hear that the original poster knows what a 4-stroking 2-smoke acts/sounds like.

 

[nickyd]

cc - i am familiar with a 2 stoke that is 4 stroking - most commonly (not only though) from a rich mixture which can cause occasional incomplete combustion...let me step all the way back. I rode the bike for about 200 miles with no problems. On the last day of my trip, the trail back home took us through some deep stream crossings....On one crossing as I brough the bike back up to speed, the engine's RPMs soared - like the slide in the carb was stuck wide open...so I killed the bike, started it back up and the ride continued. When I returned home, the bike had very little power in the high RPMs - most of my riding is tight trails so I could short shift the bike all day long and never notice the problem until the fire roads home when I would wind it out - when you would expect the powerband to come alive, it wouldn't. So I pulled the top end, mic'd the piston and confirmed it was in specs. I expected the obvious - excessive carbon on the p-valve and to not even be able to manually move it. I could - it moved freely. So I pulled it apart, scraped what carbon was on it clean - inspected everything, reassembled and threw in fresh rings. After reassembly, a fresh plug and another carb inspection, the problem was still evident - which is why I am starting to think it migth be ignition related...in the meantime while waiting to get a hold of another bike to start testing parts on, I thought I would throw this post out there...see if anybody had any kind of igniter problems or the like. And my real question - does anyone know how to test these units? If I'm not mistaken the bike uses a magneto supported CDI igntion - could it be possible the electronic advance is not occuring properly. I'm sure some will say I'm reading way too far into this but I think of myself as a fairly competent mechanic - I've done numerous top end and complete rebuilds and this one has got me puzzled. I am pretty sure I have checked the obvious but please feel free to point anything out that I may be missing.

 

[canyncarvr]

If it ran fine before a particular event, then poorly afterward, the odds are that event is pertinent, right?

When you had the topend off...did you run a rag thru the bottom end to see if it sucked in any water? See any evidence of that in the carb/boot/airbox?

Look for posts by Jaguar. He has posted a timing curve that will help you check that part out. The static timing is way advanced then retarded by the spark box at low rpm and hi rpm..with the total on the 'H' being something like
21º at 6K I believe. That figure is listed in the manual...and it's listed in the .pdf spec sheet from buykawasaki.com

I recall CDave listing resistance specs for the CDI box. Looked there?

Of course, the easiest way to test it is to put in someone else's and see what happens. If you have access to one that would answer the question simply.

Is the slide scratched? Sucking air from the top?

re: LH side and KIPS. You did see both subport drums and the main valve being activated correctly?

How deep was that water crossing?

Grounds are funny things. Make sure and ground connector is in good shape and where they attach to the frame it's tight and clean.

Any water in the magneto?

Did those rpms 'soar' with power? Or just go high...with NO power? The former could be attributed to a stuck slide (you would feel that in the throttle), the latter is a leak someplace.

If you have access to another CDI...you might as well swap out the carb, too (if the CDI doesn't 'fix' it.

Good Luck. Hope you post the resolution when you get it.