Motor surging issues!! Help!!

[KX5Zuki]

Well, I just got home from Sand Mtn. and I wasnt able to ride the KX5Zuki much because anytime I hit 3/4 or more throttle and let off, the motor surges, wont stop until I put a load on the motor, let clutch out slightly. I was worried about riding it too much because I was worried it could be an air leak. The plug shows a very rich condition. What causes the motor to surge? The KIPS works, no binding, has the mod done so no over rotating. Heres a couple pics too by the way, people have been asking about it.

[stewart]

looks like fun

[Mick]

You're too lean.  Think about what is happening...

So you're at 3/4 throttle, lets say 4,800 rpm.  You let off the throttle and close the slide, now your motor is turning 4K+ and running off the pilot jet!  Motor begs for more fuel and begins surging.  Go up on the pilot and raise the needle.

[jfabmotorsports.com]

I hope you figure it out while you can still think. Are helmets that out of style?

[Mick]

Wow I didn't even catch that!  Good eye JFab 
Helmets and bikes bro...can't have one without the other.  Ride safe.

[KX5Zuki]

I wasnt even running the full hill, just a quick little testing session.

But whats the deal with the plug saying its running rich? I understand what your saying about the lean part, but the plug is saying really really rich. This couldnt be a air leak issue?

[KX5Zuki]

looks like fun

Hey, I was trying to get a hold of you all weekend to ask if you could give me some pointers. The 707 number that kept calling. Sorry if I was bugging. Its the '86 motor that I was talking to you about.

Also, I just rememberd that I just bumped up to running 40:1 premix, meaning its running richer, correct? So the lean issue shouldnt be an issue?

[Hillclimb#42]

Check base gasket and head gasket. If its weeping oil there, its leaning out by air leak. What about throttle cable end into carb? The casing is not hanging up on the top chamber? I've seen em act that way with either one of those issues.

[stewart]

i called you back and got no answer several times  ,,how old are your crank seals

[slow600]

my bike did this from day one, before and after a complete rebuild. i researched and was told a certain amount of surging is normal with this bike. is this incorrect?

[KX500freak]

just today we fixed a complete stock 2stroke scooter,it surged from 1/2 throttle,
when we found out a cover was missing for the air-intake,which narrows the inlet.
we made one ourselfs from a cone shape ,it ran well after 

iow can it be a matter of air ,i see a big power filter sitting there,is the motor adjusted to it ?
succes

[kaw rider]

my 250 did that and the throttle cable returned slower.

[Mick]

But whats the deal with the plug saying its running rich? I understand what your saying about the lean part, but the plug is saying really really rich. This couldnt be a air leak issue?

Yes it could be an air leak.  But do understand reading plugs has got to be the worst method of judging air/fuel ratios since wofting exhaust.  Your plug essentially will only give you a very vague indication as to how rich/lean the motor was running just before shut off.  Your surging is a lean condition, period.  Be it an air leak or jetting is up to you to find out.  These bikes do have a tendancy to surge a bit when you chop the throttle...it can be tuned out.  I experimented with a couple slides and needles until I found a combination that worked perfectly.  You say you bumped up to 40:1?  From what?  But yes I think you're tracking correctly...the more oil in your gas the leaner you run hence the less oil in your fuel the richer your motor runs.  Rich or lean in terms of premix isn't about how oily the fuel is...it's about how much fuel your motor is burning.  Keep plugging away at the problem and you'll fix it.  Start with the easiest solutions first.

[slow600]

what slides/needles. do share

[Mick]

Gladly  But you're going to have to give me until the 7th to do so.  I'm in FL right now, and my KX is in ID.  In two weeks I can tell ya...