vfrpilot,

Hey, thanks for the recommendation (I should have known [:@])

I've got the #135 in and its running a lot better, but not perfect, I still have a couple of issues:

- I'm getting some stutter around 3/4 throttle
- From idle, if I goose it, it gets bogged down (at least its not dying anymore)

It doesn't seem like the APstart and length is adjustable on the TM33 like on other Mikunis, but its possible to change the nozzle.

I've got a K&N Air/Fuel meter installed and have the airscrew adjusted for best idle, the meter shows just a bit rich.

Goosing the throttle from idle causes the meter to go blank (I think this represents and overly lean condition).

Around where I'm having the stutter, the meter is just bouncing all over the place, doesn't give a steady reading. I suspect lean.

I'm considering raising the needle by a notch next. ...or should I go to a #137.5 ?

 

Following your progress. I have nothing to add that can help you, but please keep me/us updated. I've been thinking of doing the same thing.

 

If it's leaning out at higher throttle, I'd go to a larger main jet. Also, if you can adjust the fuel screw while it is running, I highly recommend you adjust that as described here after upping your main jet:

http://www.thumpertalk.com/forum/sho...d.php?t=327405

 

Ditto.

I've got a similar setup (or will have shortly, thanks to vfrpilot), but I'm at 600' elevation,and I've got the airbox lid on with a single, KDX snorkel, so maybe we're still close.

From everything I've read, jetting starts with getting the main jet right for WOT, then working your way back towards idle. So based on your 3/4 throttle stutter, I'd suggest the #137.5 main jet first, then tweak the needle afterwards.

 

Went to a #137.5 and didn't see much difference except the stutter seemed to moved down in the throttle range, seems to be kind of at mid range now. I have main jets up to a #145, but I think I'll play with the needle next.

I've only have time for 1 or 2 trials after work each evening, so this may take a while....

Yes, I'm adjusting the air/fuel screw too each time. Seems to idle best ata bitrich (according to my meter).

 

Here's the results of today's trials:

- MJ #137.5, 3rd clip (same as yesterday), but this time I put the airbox lid back on ( I have a KDX snorkle in it)

Idle was OK, but went real slow off idle so as not to activate the A/P - noticed that it was going really lean according to my meter
No test ride

- Verified operation of A/P (never suspected it, but checked just to be sure), getting a squirt upon twisting the throttle

Suspected the needle position was causing the overly lean condition - so I dropped it to the 5th position (airbox lid is still on & 137.5 MJ)

With no load, idle OK, slow throttle and the meter is glowing steady in the rich area up to 1/2 throttle where its richening up

Test drive: Best situation with this carb so far. Still have a bit of a bog off idle when goosing it. Strong acceleration throughout.
midrange stutter is now gone. Meter indicates rich 1/4 -> WOT (maybe time to back off on the MJ?) Getting some popping on deacceleraton.

- Same setup: 5th pos, 137.5 MJ, except I took off the airbox lid again --- YUCK! It's barely ridable again.


Conclusions, theories, speculations, hypotheses and guesses:

- Airbox lid on/off makes a BIG difference - my luck so far has been best with it on, so I'm keeping it on for now
- Off idle bog may be due to A/P not starting up early enough (too bad its not adjustable on the TM33 AFAIK)
- I'm too rich now, but running good - I'll either drop the MJ or lower the needle (clip goes up) (maybe both?)

- I figured at my altitude, I should do everything that I can to get as much air into the engine, that's what prompted me to remove the airbox lid in the first place. Even though I'm getting more air into the bike, it does contain less O2 than a sea level (it's less dense).

- The erratic behavior of the meter might be interprepted as things being lean -- now that I see what a steady rich reading looks like

- It might be best to start out too rich and work backwards from there? I started out too lean

- I think that I'm getting close now...

 

This is how it goes, congrats on the progress. It takes doing this fiddly stuff to get an engine that runs correctly at any altitude, and the higher altitudes usually are the ones people have less experience with, in general, so there is just more hunt and peck to find that just right set up. I know Bill has ridden for many many years at altitudes up to the top of Mt.Antero, 14,200 ft., and he has the knowledge to jet bikes for those uses. But it sounds like you're homing in on the set-up you need.
One piece of advice, if I can; I ran around and around doing this with an RD400 two stroke twin back in the late 70's. I had different compression pistons, expansion chambers, K&N's, the whole drill. I must have tried a dozen combinations before I got it just right, and doing it on 2 carbs each time!
I found after the 2nd try that I should write it down, each step. Pretty soon, a pattern emerged and I started moving in the right direction. It helped me, anyway, get the bike running just perfectly.

 

Here's some advice to me from Bill:

"I spoke with our Kawasaki dealer today he is a lot like me, cant leave anything alone & love performance. He said the needle & needle jet may be to small causing you to go lean. He said to remove the main jet & start the bike it will start without any problem. Run the bike through the RPM range as you did before removing the main jet. If the bike doesn't change the way it runs then the needle & needle jet are to small if it runs rich then its OK you need to keep jetting."

 

Took last night off, but got to work on the carb a little bit earlier today.

- Took Bills' advice and removed the main jet, needle was still on the 5th clip down and the airbox lid was off. It had erratic idle and was lean on gradual throttle.

- Put the airbox lid back on with the same setup. Idle was good and was rich on easy throttle.

- Moved the clip to the 4th position down from top. Still no main jet installed and airbox lid on. Running a bit leaner. Pretty good response on goose and a little stutter on easy throttle just off idle. Test drive: low-midrange only, feels great, meter shows it still being a bit rich - goosing it gives very strong response.

- #135 MJ now installed, clip @ 4th position, airbox lid on. Meter is showing it rich through midrange - but not off the scale. Some surge around 3/4 throttle. It's running the best here so far. Can't just "floor it" off idle, need to ease into the goose. Suspect need to raise clip and/or drop the MJ by one. WOT - getting pulsating on the meter (rich/lean/rich/lean/....) Idles best at a bit rich. (Don't adjust the screw to "ideal" A/F ratio).

- Moved clip to 3rd position, (MJ still @ #135 and airbox lid on), midrange erratic - stuttering, meter pulsating

- Moved back to 4th position on clip, running great again


Almost perfect now. A couple of concerns though. Slow throttle off idle gives a small hiccup around 1/8-1/4 throttle. WOT gives a small surge and some pulsating. Rolling goose gives strong response, almost pulling up the front wheel. Normal street riding is just fine, strong steady midrange, but need to be aware of the small flat spot off idle.

Looks like if I want to run with the airbox lid off, need to up the needle jet and/or jet needle. (I'll just keep the lid on.) I'm going to drop the MJ to #132.5 tomorrow and see if that makes WOT any better (or worse). Playing with the screw might tune in the low end flat spot too. ...almost there.

 

Dan, I too am tuning with a new TM33 for an XR250R and find a lean spot right off idle that I can't seem to fix. The KLX and XR are really similar to tune in my experience. The dealer where I bought the carb has said another customer also has the same flat spot. He is researching different needles right now for me.

I've tried running pilots from 30 to 40, and also have both a P-6 and P-8 needle jet. I have things running well overall now except for the flat spot, and with the pilot screw only .75 turns out (35 pilot, P-6 needle jet, 5th clip, 142.5 main), which doesn't seem right. My next thing is to try both:

-30 pilot (really lean) with the larger P-8 needle jet and the needle dropped down with the 1st clip to try to richen the extreme low end using the needle jet. When I tried the P-8 with a 37.5 pilot all was really too rich, so I hope this weird combo will be revealing.

-42.5 pilot, P-6 needle jet with needle all the way up in 5th clip. The pilot circuit of this carb is bizzare. I know this pilot will require the pilot screw at only .5 turns out, which would be a red flag of excessive richness with other carbs.