My KLX351 has a weird idle and is occasionally hard to start (and I've never been able to kick start it). It won't idle reliably below about 2500rpm, and the idle often hangs or is slow to return to idle if I blip it. Like it takes about 2-4 seconds to go from 8k back to 2k. Sometimes i blip it and it will hang basically forever at high rpm until i blip it again and will settle at 2500. If i adjust idle throttle to 1500, it goes up and down quite a bit and will eventually just die. I've tried adjusting the fuel/air screw and seems to get worse less than 2 turns in, but anything more than 2 turns i cant really tell a difference.

I've checked for vacuum leaks and didn't find anything definitive. Leak down and compression were decent, if i remember right, like 80% and 95psi respectively (without messing with the auto exhaust release). Valve clearances have recently been adjusted, checked timing. Recently did a full carb clean, checking each fuel jet (didn't remove air jets but did run carb cleaner and guitar wire thru them).

One thing I noticed (and Bill noticed when i sent in the carb for rebuild) is that the slide is pretty worn. There's enough play that i can push the slide back and forth and feel it. In the pic below, I have the slide pushed towards the 'bottom' of the pic. Circled in blue, there's enough clearance where you can see the carb throat between the slide and carb body, maybe 0.030". If i push the slide all the way "up" in the pic, theres about 0.020" clearance (with a feeler gauge) between the slide and the carb body.
Is this crazy? My next move is just to replace the carb but its pretty expensive ($450) and i'd be pretty bummed if this didn't do it.

 

Did it ever run right with that carb?
I would try new jets before ordering a new carb. Drop your pilot jet 1 or 2 sizes, same with the main. What mods do you have on the exhaust?

 

It has never run right for me with the carb. The guy I bought it from (he put the bill blue kit in) claims it was great but I don't know if I believe him
I don't remember the numbers, but bill already had me rejet it with not much change in performance
The airbox has the snorkel removed and the exhaust is a muzzy. I had repacked it at one point

 

Don't even bother with that carb. Given the slide wear and lack of response to change I would just replace it. Get a TM36-68 pumper. The TM33 is smaller than the stock CVK, it's just bored out to a 34. the 36 will flow more air which the 351 will like. I put the TM36 on my stock bore and it's a night/day difference, I'm sure I picked up a few HP (dyno session coming soon). I am certain the TM36 would be much better than the 33 for a big bore. I paid like $260 for the TM36 on Ebay, best mod for the money in my opinion

 

I agree. Stop messing around.

 

You've got a 351? How did it fit? Did you need to get special boots?

That's definitely attractive. Bill wants $450, and I think it's a TM33

 

I dont have a big bore, bike still has the stock bore size, 250 (my tag line/signature has my bike setup). i have all the mods done and the stock carb crapped out so i replaced it with a better one that was cheaper. i was going to get the TM33, but after going on here and talking to some very knowledgeable people i went with the TM36. it was literally plug and play. no adapter boots, no cutting anything, nothing. removed the stock carb and installed the TM36. the only thing i had to do was re-route the throttle cables. the carb Bill Blue sells is a TM33 which is smaller than the stock CVK34. he just modifies it and bores out the center to make it 34mm. it will have much more adjustability than stock, but doesnt flow any more air so power gains are limited. up the size to 36mm and you allow more air (and fuel) into the engine which will result in more power. just make sure it is tuned and jetted PROPERLY (as in Log AFRs and make change accordingly, DO NOT use a "butt dyno" as your results will not be correct). i found the "stock" TM36 set-up was EXTREMELY lean at around 17:1 AFR @ WOT, but the bike felt great so I thought the jetting was close. Glad I got a dattalogger and started reading AFRs otherwise I probably would've cooked it