All 2st throttle hesitation

[Steve ROC]

I have a 2006 WR 250, Mikuni carb, jetted for 2200 feet, FMF Gnarly pipe with Turbine Core 2 can. I'm suffering from bottom end hesitation that is sucking the fun factor out of riding and making me wonder why i sold my KTM 300 2 weeks ago. I have a Keihin 38mm carb here and new reeds on the way. Any ideas on how to elliminate this hesitation? Power valve problem? i need throttle response, right now it reminds me of the early '90's Kawi KX's. Crack the throttle and it's, pause, pause,pause, zing. I like the zing, don't like the pause. Hope you have some ideas.

 

[Rusty 2]

Hmm, never had a 2-stroke do that before. XR400s used to do that in stock form,...we called it the "off-idle bog" over on TT. The fix was uncorking and re-jetting and/or a pumper carb. I'd say that Keihin is a step in the right direction,...it may be a lean bog.

 

[raisrx251]

Something is not right for that bike to have a hesitation. Sounds like jetting/air leak? My '07 was instant, there can be a little hit about 1/3 throttle but that was smoothed out with the Keihn PWK. Is there anyone in your area to compare your jetting too? Anyone on here?

 

[PC.]

Is the Keihin on the biek now or do you have it and are waiting to install it?

My buddies stock 06' WR250 does not have a stumble off idle, so its certainly not a bike attribute. If you're riding at elevation then you might be too rich and just need to lean out the pilot and possible the needle.

What carb are you running and what jetting does it have now?
Start with the simple and cheap options before diving into the motor or replacing parts.

 

[ARod2000]

I like the zing, don't like the pause.

That's funny.

I have the same year, same pipe, same carb - except mine rips from bottom to top. If someone doesn't post the jets that work on this bike I'll open up my carb and tell you what jets I have. I know I have the JD needle and whatever jets they recommended. I just don't remember what they are.

Have you tried cleaning the carb? Sounds like one of your circuits isn't working properly. I'd start with a disassembly and thorough cleaning

 

[Steve ROC]

here is the current setting that has been in the Mikuni TMX for 2 seasons:
Piolot~32.5
Slide~3.0
Main~380
Needle~61 middle position
will clean carb today and replace reeds.

 

[MOTORHEAD]

It could be the reeds. My '07 had no bottom and I found the reeds to be bad.

 

[krieg]

I was kinda thinking reeds too. Also, have you checked the silencer packing? When it goes bad and starts clogging things up, bad low end is usually the first symptom.

 

[wallybean]

Steve,

At your altitude it should rip everywhere with that jetting(even with the TMX). I second that the reeds might have a problem. Maybe some curled edges/cracks. When you go to the PWK start with a CEK needle in the middle, 45 pilot, 168 main. That will get you close. I am several thousand feet higher and use a CEL needle(all else the same) with flawless results: idles, rips throughout the range, and really flys on top. My problem with the TMX was always trying to nurse an idle out of it at altitude with a rekluse pro. The Keihin will be better everywhere though.

Walt

 

[MOTORHEAD]

The Keihin will be better everywhere though.

Walt

Amen brother.

 

[Norman Foley]

Amen brother.

"Kult of the Keihin"

 

[Steve ROC]

put new reeds in, helped a bit
changed carb to 38mm Keihin, still hesitant but not as bad but now starts sputtering once the revs start climbing. bike sounds like it is hitting a rev limiter now. bike feels lean and wont pull gears. still not impressed, on the up side, the bike will idle now and I was able to use the stock throttle cable. I am happy about that. I'm still wondering if I botched up the power valve when I did a top end. made sure the dimples lined up and checked everything acording to the manual.
jetting from Sudco in the carb:
needle~DDJ center position
pilot~50
main~175
slide~#7

 

[MOTORHEAD]

"Kult of the Keihin"

Yep, you got me read handed cop'er.

 

[MOTORHEAD]

put new reeds in, helped a bit
changed carb to 38mm Keihin, still hesitant but not as bad but now starts sputtering once the revs start climbing. bike sounds like it is hitting a rev limiter now. bike feels lean and wont pull gears. still not impressed, on the up side, the bike will idle now and I was able to use the stock throttle cable. I am happy about that. I'm still wondering if I botched up the power valve when I did a top end. made sure the dimples lined up and checked everything acording to the manual.
jetting from Sudco in the carb:
needle~DDJ center position
pilot~50
main~175
slide~#7

That pilot is way to big and the needle's pretty rich.

if you didn't change the open and closed stop settings on the PV then it should be easy to tell if they are right. Just pull the covers and pipe and see if it's on the closed stop with the subs closed. Pop the linkage loose and move it through it's stroke and see if everything opens up all the way be fore it hits the top stop.

 

[Steve ROC]

so if everything else is so rich, why dose the motor pop and spit in higher rpm. its doing this even with a 200 main in it now. Plug is white and idle smoke is white. I'll deal with the needle and pilot when I can get the bike to run without melting down. everyone says the bike is rich, but the bike and plug tells me its lean. what else do you have?