Adjusting the CVK-34 Carb
 

Bike:
2006 KLX250S

Modifications:
KLX300 full exhaust (plug removed)
Air Box lid off
"Y" mod
High flow air filter
Smog assembly removed
DynoJet 2206 Kit
124 main jet
Clip 3rd groove from top
'T' handle 2.5 turns out

Issues:
1. Revs return too slow to idle
2. Idle either too High or too Low
3. Decel popping with a "psssst" from time to time

I installed the jet kit and took it down the road a couple times and it ran great. Went riding with a friend and all was well at first. First hill we came to had an unexpected jump at the top; landed kinda hard and stalled the bike. Once it finaly fired the issues have continued; lots of decel popping and when you pull in the clutch the idle hangs around 4-5k before slowly dropping to 1.5k.

-I sprayed WD40 on the Idle knob connection to the carb
-Checked twist grip; operates smooth and returns to closed
-Checked cable connections at carb; little slack and not too tight
-Tried adjusting idle with idle knob; sometimes it idles fine at 1.5k and the throatle picks up good, other times it idles 1.3-1.5k and bogs a little when opening throatle. Adjustment of idle with knob is futile; tiny movement drops idle low or too high (4-5k)
-Played with the 'T' handle; currently still at 2.5 turns out


I am pretty sure the "pssst" sound from the front and the excessive decel popping is from an exhaust leak. I used muffler silicone and a new header/can gasket but I am sure the head/header gasket needs replacement. Will exhaust leak cause all my current issues?? I think when I landed hard I cracked/broke loose the silicone seal and my issues began.

As with most OEM parts on the 06-07 bikes; the gasket is currently on back order.

Anything I can do in the mean time or with the gasket resolve my issues??

Thanks!

Finally received the gasket and installed it last weekend; the gasket did need to be replaced but it did not resolve my issues. The front "pssst" seems a little better but not completely gone. I rode the bike twice then tightened the header bolts one more time.

My next steps are:
1. Check for kinks or improper routing of the throttle cables
2. Check to make sure both sides of the carb are seated to the boots.
3. Still lots of decel popping so I may try going up to a 128 main jet while I am checking the above.

If your decel popping is due to a lean condition, its not likely the main jet as the main should (edit: NOT) be flowing with the throttle closed.

Found two old posts related to my 'slow return to idle' issue.

1. "Drilling slide hole too large could cause this." I used the drill bit provided with the DJ jet kit so I don't think this is it. I did not use the bit included for drilling out the air mix screw cover.
2. In a post, the carb was adjusted before a high altitude ride; he went from a 40 pilot down to a 35 and experienced the slow return to idle. Could I possibly need a bigger pilot jet? Would the larger pilot jet also help with the decel popping?
3. "improper adjustment of the two throttle cable connections at the carb can cause a slow return to idle". This could very likely be part of my problem; I have tinkered with this. Is there a link to properly adjusting these connections?

Thanks!

Ja,
See my main jet post above and I left the word "NOT" out. Sorry if any confusion.

I don't think the main should be part of the equation for slow return to idle.

You should drill out the cover from the mix screw as a turning this mix screw out a little could help with your problem. I would not advise just changing pilot jets without the ability to adjust the mix screw. The mix screw works in conjunction with the pilot jet.

I would think drilling the slide hole too large could cause the slide to rise and fall too quickly, not too slow.

When my bike was all completely stock, it would return to idle a little slowly. I attributed this to being a bit lean on the idle circuit. Perhaps opening the mix screw a little would have changed the situation, but I went more with pipe, jet kit, etc at same time so can't tell you.

Does your throttle "snap" back into idle when you let it go. Can you see the quick snap back on the carb linkage. There should be very little to no hesitation here. If there is, look to your throttle cables, etc. and find where its sticking. I don't know of a link. I do know there should be a little slack so that both pull and return cables should not be tight at the same time, and with throttle closed there should be a slight bit of slack in the pull line. Adjustments for these cables are at the carb.

I did drill out the cap and installed a 'T' handle so I can adjust the mixture. What I was trying to say in my previous post is that I did not use the wrong drill bit to enlarge the slide hole. I'm currently at 2.5 to 2.75 turns out.

My throttle snaps back; no hesitation that I can tell.

I may have the return cable a little tighter than the other; it is still by far not 'tight'. I will take another look at it though.

I am going to look into getting a Cable Lube Tool, nice tool to have and it will eliminate a sticky cable as the culprit.

I could have slightly kinked a cable when re-installing the tank so I need to look at that as well.

The odd thing is this: between 1500 to 5k rpm I experience the slow return to idle. But above 5k when I pull in the clutch to change a gear I can feel & see that the rpms fall normal/quicker. Riding the roads is a non-issue; crawling over rocks is a task with a high idle!

I may have found the problem! The cap came off the top carb vent that I plugged when I removed the smog plumbing. I did not secure it the first time. It now has a cap and tight zip-tie. Don't know for sure but will find out tomorrow when I ride it. fingers crossed!

Issues with idle and excessive decel popping FIXED!