Hey to all. Well, I recently installed the BB 351 and I am really pleased on the power and performance. I have the stock carb on it it, and replaced the needle,pilot and main... I set the idle to 1400 rpm, then rode it, and sometimes it idles to low whereas it kills the engine or sometimes it idles up around 2500 rpm without ever adjusting the idle manually, and all this happens during the ride when I come to a stop or a slowdown. When I start it up, it seems to be fine, only during the ride am I having problems. Just wondering what it might be? I appreciate any advice...

 

i had that prob on my klr650.one of the tiny holes or jets must be cloged.

 

try the tm33 from bill, its wonderful

 

Pilot may be too large. had the same prob' when I fitted a #40 pilot. #38 pilot cured it.

 

Sounds like an intake leak. Spraying carb cleaner on the area while running will tell you.

 

Ok, thanks everyone! I'll try the carb cleaner and than the smaller pilot. Really appreciate the info!

 

Thanks Phil

Apparently the factors dont have any and have said its main dealer only. Depending on cost / availability then it may well be a trip to the breakers.

Thanks again for your help.

 

Beasty, i had a similar problem after my upgrade although mine was just the opposite from what other are reporting. I had kept the stock pilot when i upgraded (all i had at the time) (upgraded to 132 (?? i think) main. had similar probs. i was running air side free mods, K&N filter, stock carb and exhaust. Was running stock pilot before upgrade and 128 DJ main.

I upped the pilot to a 40 this weekend (two sizes up) and it runs just like i put the DJ kit on it originally again. Took care of the erratic idle and low rpm run. backed off on the mixture screw a bit too (around 2 1/3 turns out). (now the front end is coming up in 3rd

(clogged pilot i think would also act the same way too though, but if you changed it out i wouldnt think thats your prob though).

 

I am having the same issues with my KLX 351. I actually rode down to Bill's house and we put it in together a week ago. Riding back to Kansas City was the break-in period, so it took me almost 8 hours. That was a long trip!

Anyway, it was running awesome, but then suddenly it wasn't. Now it doesn't want to idle. When it's cold, it will idle high. Once it's warm, it idles lower and lower until it bogs and dies. I have to keep giving it throttle if I pull the clutch in.

The carb was rejetted when we put in the big bore. Currently a 132 main jet and a 42 pilot. It seemed to like it that rich and rode and idled wonderfully. Smooth, steady, responsive, predictable...

And now all of a sudden, it won't idle steady anymore. It wanders all over the place and then bogs and dies. I've checked for vacuum leaks to no avail. I tried running with the gas cap open to see if that was the issue. No change there either. Any other ideas? I eventually plan on swapping the carburetor for Bill's TM33, but maybe I'll have to do that sooner.

I have and have always had a slight exhaust leak from the header to the FMF pipe. Bill even noticed it when we were putting the bike back together and said it was not bad enough to make a difference. And, sure enough, it didn't seem to effect idle or throttle response, etc. But maybe it has gotten worse/too bad?

Next up is the check the float and air screw settings. I'm thinking, also, of running some Seafoam through the tank to see if it's just a slightly clogged pilot jet. Main jet seems great, because it still runs like a champ...

Well, no, there is a big of surging and hiccuping at speed. It's very, very slight, but I do notice it now that I think about it. After more than 25,000 miles, I notice the slightest little things with this machine.

Any ideas, ladies and gentlemen?

Oh, and here's the 351 on the first start up after the rebuild:
KLX250 to 351 - Fire it up! (with FMF Q4) - YouTube

And here it is on its first track day after break-in:
KLX351sm- Helmet Cam Track Session UNCUT - YouTube

 

This sounds rich in the pilot circuit, like how my bike runs with the choke lever pulled. A #42 sounds big to me. See above where mattyw is using a #40 and WestOzKLX went from a #40 to #38. Did the fuel screw back out? Does turning the fuel screw in or out improve/worsen the idle?