Off Idle blubber normal?

[white knuckes]

Okay, to qualify this question I don't want to open up a jetting thing that is probably beat to death on this forum.

Trying to dial in a used 200 adult modded bike that came with a Gnarly/Turbine II, no air box lid and a strange Keihin PJ series carb. So here's the deal: With instant starting and smooth idle all seems well. Coming off idle in that first 1/8-1/4 turn the engine blubbers around like it's loaded up and then comes on like a freight train pulling hard through upper revs.

The last 2-stroke I owned had this same issue no matter what was done. 4 strokes seem smooth and linear through that range. Before I enter into jetting voodoo is this normal for 200's? Are they choppy off idle? Could you cruise along at 1/4 throttle or is it roll it on to go?

 

[dsndblm]

You can make it go away. I had to go with smaller pilot and go with a CEK needle. First off try raising the needle clip one notch towards the top of the needle to lean it out a bit. Read the jetting section of Daves tech tipsm, watch the plug and be patient.

 

[white knuckes]

dsndblm, Nice to know someone solved for it.

Uh, call me a ninny but where might I find "Dave's tech tips"?
I have searched this form and DR site with no luck.

 

[JasonWho]

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[white knuckes]

JasonWho, Thanks for the navigation tip. Thought the tech article might be specific to 200/220 tricks. I've had the bike and discovered this forum for about a week so haven't tweaked much yet.

I have considerable experience tuning but mostly 4 strokes. I'm sure the same theory applies to 2 stroke tuning but tuner tips are handy for a reference point to begin.

I needed to make sure the effect of off idle blubbers wasn't a common thing nobody can beat. Thanks all and no, I won't ask what is the best jet to use or what color pipe works best under water.

 

[canyncarvr]

A 200 response can be smooth as you wish...from any throttle position.

'Opening up...' a jetting situation is exactly where you need to go............

Sorry 'bout that. :(

re: 'Could you cruise along at 1/4 throttle or is it roll it on to go?'

The answer to the first part is, 'Yes.'

The answer to the second part is also, 'Yes.'

I guess I don't understand the question...............:think:

 

[m0rie]

Have you pulled the top end and check the condition of the reeds, kips valve and rings? You haven't posted what your elevation/temp and jetting exactly is either?

-Maurice

 

[white knuckes]

canyncarvr, what I'm trying to communicate is questioning the 1/8-1/4 throttle low RPM smooth factor. The engine is blubbery in this range sounding rich and loads up where a blip on the throttle clears it. Rolling on the gas makes for even pull and she comes on strong all the way up. Mid range and Main are fine.

I know I'm dealing with the idle circuit (pilot jet), and or needle clip/ taper issues. I've riden MX race bikes that have the same deal they run funky off idle but roll on the gas and they hit - hard. Maybe they don't bother to tune 'em.

m0rie, will do a complete top end inspection this winter, trying the simple things first. The problem with a used bike is I don't have the history and am dealing with a Keihin PJ carb swap which has an oval slide, the jetting/needle could be way off. I have no clue why they pulled the factory carb.

 

[canyncarvr]

That is (somewhat) a needle issue that is common with the kdx (and other 2-smokes, too). The diameter is too big (lean) to make up for/mask the fact that the slope starts too early (small taper angle). Still, with some attention paid to tuning it can be largely reduced if not eliminated....but won't be as good as it could be until you get into a steeper º needle along the line of a CEL (with the oem #5TV). A more-lean TV will help, too. Ron (RB-Designs) will machine your slide or just plain sell you one with the cut of your choice. He knows which slide to use, too! I (and others) have ordered slides from various vendors only to have repeated errors in getting the right size!

...and they cost more than what Ron sells 'em for, too.

I'd call the PWK slide 'oval.' It certainly isn't mikuni-flat! Subtact a couple of hoses...does your carb look anything like:

this? (post#20)

 

[JasonWho]

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[white knuckes]

Thanks for the input and support gents.

Basically I have varified it is a PJ model not PWK (the stock flavor). The problem begins with a voodoo rejet attempt with an unknown carb. The PJ is used on ATV applications it's hard to say why the factory PWK was swapped but my guess the guy thought bigger is better. I haven't calipered the bore yet but it's probably a 36mm +.

Solution: I will order a new 35mm PWK and have a jetting start point from this site's Tech Tips with current pipe/airbox configuration. I e-mailed Ron (RB-Designs) and he replied "get rid of that PJ they are hard to get the low speed circuit dialed and if you do they won't idle".

Used bikes: you're buying someone elses R&D headaches. Grrrr.

 

[m0rie]

I hear you on that :-) My '89 had "issues" when i bought it...Got most of them whipped into shape now though :-) You might be able to offload that PJ on E-B-A-Y they were also used on some moto-x bikes (my bro's 94 RM 250 comes to mind). With a PWK you should be able to get it dialed in pretty quickly.

-Maurice

 

[white knuckes]

Now the original question revisited. Do most KDX's run smooth off idle? Example: just crack the throttle open 1/4 turn in a tight woods situation in first gear.

A. Do they run smooth and even (insert sound effect): eeeeeEEEERRRR as you move along?
B. Or do they Bla, blat, sput, BLAT kick around until you clutch it and rev to clear or just grab a handful of throttle making for a rocket ride?

Mine currently would be B. Very uneven until half throttle where it cleans up. Idle is strangely smooth.

I am gonna hate putting on a new PWK to find with proper jetting it duplicates the same problem.

 

[m0rie]

B. Or do they Bla, blat, sput, BLAT kick around until you clutch it and rev to clear or just grab a handful of throttle making for a rocket ride?

Mine currently would be B. Very uneven until half throttle where it cleans up. Idle is strangely smooth.

I am gonna hate putting on a new PWK to find with proper jetting it duplicates the same problem.

Even with rings and a piston that was so amazingly worn that i'm suprised it had compression my '89 was never like that. It just had no low end until about half throttle when the pipe came on. And that was with stock jetting. In reality the only difference between the PJ and the PWK (as far as I know) is the lack of an idle circuit. Most MX bikes that use a PJ have a screw in the throttle that is adjusted to hold the throttle open enough to idle. On my bro's RM250 it has to be held about 1/8 throttle to idle. What is the jetting and needle that you currently have in the PJ right now? You should be able to use the same jets and needles as a PWK.

-Maurice

 

[white knuckes]

The "same" jetting and needles as a PWK was one of my thoughts as well. The PJ line is strange there may be a 35mm out there but the PJ model is discontinued. My fear of hair pulling is based on if it is the more common 36mm buggers all 35mm PWK jetting/needle data is invalid..

I'm pretty committed to go back to the "known" PWK flavor and start fresh. The PJ idle adj. is performed by rotating the choke pull knob this is cool and can be done with a glove on! hmmm, so much for that feature.

 

[m0rie]

Well there are a couple people out there in KDX land who have run 36mm and larger carbs on their KDX's (FredT I think was one of them) and didn't have jetting that was too dramatically different than the normal "correct" jetting. Your going to have to buy the same jets for the PWK so you might as well get started on it by "testing" with the PJ and some new jets (since they use the same ones). I'm still curious what the PJ has for jets and needle in it currently.

-Maurice

 

[m0rie]

BTW - I'm all for you getting the PWK and moving along that way. But I don't think there is any real reason that the PJ shouldn't work _better_ than it does now. Maybe not as good as a PWK but certainly better than your describing. If you do decide to get a PWK you might has well "upgrade" along the way and get Ron at RB-Designs to do you up a PWK or Airstryker.

There are very likely other factors at play here as well. You probably should check the KIPS side cover and see if you have a bunch of spooge (unburnt oil) built up in there. If you do, then your KIPS is gummed up and a) trying to strip its teeth and b) not working as well as it could. Also if there is a bunch of spooge mostly likely the pipe and silencer have accumulated a large quantity of said spooge as well.

-Maurice

 

[white knuckes]

m0rie, solid advise, thanks! I too believe the PJ might be worth a run at it as the jet range will be needed anyway. It was the needle I thought might be way off model to model. The seller rode it as is.

In my first week of ownership I've ordered a manual and completed needed basic maintenance. Now the easy stuff is done so I need to buck up and go into the carb and try a couple jets down on the pilot and/or raise the needle clip. The problem is the local Kawasaki dealers never seem to stock anything like jets or even the KIPS cover gasket (I called). So I can research, test more and place an order for next week.

I'll post the jet findings when I get in there after this weekends trail shakedown tests. Two questions: Can I inspect the KIPS without a new gasket ready to go? What is the definition of "four stroking"? I read a post where a guy describes this condition as normal for a 2-stroke to blubber around at low speed with no load.

 

[JasonWho]

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[m0rie]

You can pull off both KIPS side covers. If your careful the gasket should come off without any problems. If it doesn't, just put some high temp RTV in a bead on top of the gasket. Let it setup overnight and it should hold without any problems.

You should order a whole top end gasket kit. Cometics makes one for around $20 I think. It will have everything you need (gasketwise) to tear down and inspect the top end then put it back together.

If you pull off your pipe to inspect it you can put a bead of RTV between the two orings. This helps seal the case to pipe junction. Also when the reeds start to get frayed and chipped the bottom end suffers. When you pull out the carb to check the jets and needle, pull the reed cage and take a look at them. If there are still a pair of duck bill reed stops then they are the stock reeds (most likely original) and most certainly are not helping things :-)

I'd be willing to bet the PJ has some amazingly large pilot and main as well as a wanky needle. My bro's 94 RM250 with a PJ came with a 52 pilot and a 172 main. If you've got similar jetting then thats 90% of your problem. Your bike is going to be looking for something more along the lines of a 42 pilot and a 152 main. Give or take a bit for elevation/temp and needle. When you pull it apart post the pilot, main and needle code. Most likely it will be something like R1732 or similar. We'll have to translate that to a Keihan code and see what we get.

-Maurice

 

[canyncarvr]

34 or 38mm?

I wanna see a picture of white knuck's slide.

Email it to someone that can post it?

 

[white knuckes]

Thanks again for supporting my newbee-ness in the thread that won't die. The whole KIPS thing has got me convinced a proper inspection is a must. Gonna play with the new toy over the weekend before I find true evil lurking. The reed suggestion is cool and indeed probably the factory fit.

I am also betting the PJ was moved across by some idiot with no thought the jetting might be addressed. I think I'll at least take a peak at the pilot/main and raise the clip a couple notches tonight. The mystery parts will be fun to see how "out there' they are. Who knows a lucky rejet and new needle and this PJ could be the new sought after KDX mod......naaaa.

~Gregg

 

[m0rie]

I am also betting the PJ was moved across by some idiot with no thought the jetting might be addressed. I think I'll at least take a peak at the pilot/main and raise the clip a couple notches tonight. The mystery parts will be fun to see how "out there' they are. Who knows a lucky rejet and new needle and this PJ could be the new sought after KDX mod......naaaa.

I doubt it becoming the new hot mod but you never know :-)

By all means take a peak at the pilot/main and needle and post what they are. Inquiring minds want to know.

-Maurice

 

[shr]

Good luck on the PJ......, At least the jets are the same as the PWK's and after hitting your head aginst the wall (till it hurts to bad) you can put those jets and or needles to good use on your future PWK!

 

[white knuckes]

Okay, the verdicts in. The PJ carb bore measures 35mm., Main 155 (not bad), Pilot 55 (wow), needle is a mystery stamped "CE G", clip center. Condition very good no slide wear etc. and the slide is not a flat side "D" shape it's an oval. Off to the shop for a 42-45 pilot will post the result.

Anyone who can decode the needle please reply. The not so nice guy at the shop can only use OEM part numbers off the micro fitch. I think the R1173L might be the ticket but they don't have one.