All 2st Basic carby queries

[rockdancer]

Just some queries from a novice at carby tuning
I have the TMX 38
Q1
can anyone help on main Jet Identification
The only ID on my main jet is U8F ?
Nearest code in the parts catalogue is 8U00 72310 - which is a 380
which is possibly right as that is what it says in the manual

(The fuel nozzle under the jet looks like a 633 5?JR- 5 - I guess they are all the same)

I want to go to a 450main or so to see how it runs but I am concerned
about being rich . It seems to run rich at times and lean at others.
(I ride in temps ranging from 5 degrees C to 25 C in one day and varying altitudes to 700m ASL)

Q 2
Slide has an ID of P2 and a 1 on it this doesnt seem to relate to 4 or 5 on others specs.

Q3 Whats the trick to removing the throttle cable in the slide to check needle position ?

Thanks for any help

 

[Norman Foley]

First off... Your '08 TMX38 is a different model than '09-'10 TMX38. Wallybean refers to the '09-'10 model as TMXX to avoid confusion. They use different needles, main jet size range, completely different shape slides. If you read TMXX specs in threads, you will be totaly confused about your TMX specs.

Jet ID... I bet you are holding your jet with the three numbers at 12 o'clock looking at it. 380 would look like 08E or if slightly obscured maybe U8F. Hold it so it is at 6 o'clock. Stock size for your bike is 400 (richest), going down to a 370 (leanest). 390-380 most common settings. You wouldn't need a 450 Ice racing in Antarctica in the TMX, but this is stock main jet in a TMXX with the Power Up kit.

Main jet nozzle or needle jet is R5, but can be changed. I think as the number goes up the needle jet is leaner. Joe Chod ran an R7 in his '07 WR125.

Slide ID is on indexing lug on slide. Hold the slide with lug up and number is next to little logo box. Stock is 3.0 4.0 is a common change to lean out carb. Different carb, different range on slides.

If you pull back spring and look down slide, you'll see retaining nut has a notch. You have to push cable down and slide it out of the notch. To access needle you have to use 6mm socket to loosen and remove nut. Be gentle, as you can crush the soft nut together at the notch.

 

[rockdancer]

Thanks Norman

You are right it looks like o8F but the right way around it must be 380 .. duh

3.0 slide. R5 jet nozzle - Idle jet 30 also hard to read - long day
all stock then
I think needle will be in stock location


Thanks also on clarification on jetting and carb differences I couldnt work out why they were saying 450 , 460 470 etc

Spark plug is looking ok if anything a bit rich looking - like light chocolate
bike not pulling well from low rpm on hills - hard to get on the pipe
doesnt sound real clean when on pipe sometimes
Any ideas on jetting for this carb in a warmer climate? 80 - 90 deg. & humid .
try leaner 370 main ?
Just trying to delay inevitable switch to a PWK

 

[john01]

Good info Norman I have a 08 Cr125 and was wondering why guys ran 450's and up on the new WR's. I currently run a 410 in my bike with FMF fatty and FMF PC2 and it feels close. Thanks.

 

[rockdancer]

Tried postion 4 on needle and running worse - too rich

 

[Kevin_TE250]

Tried postion 4 on needle and running worse - too rich

just get a pwk... I've tried and tried to get mine to not run so rich I'm down to 17.5 pilot now... I don't have the cash for a PWK so I'm gonna run it the way it is for now.. but I will get a PWK when I get the funds up... the tmx sucks...

 

[dirt-dude]

Kevin I usually run 25-30 pilot, 60 needle in grove 1 or 2 and 380
main on 01-04 cr-125's at approx. 1000ft 44-1 premix. You may
want to check your float height and crank seal on the clutch side.
I haven't had the issues with the tmx some have, but my riding
altitude range only varies 500 to 2000 ft.

 

[rockdancer]

I tried groove 2 and it after a quick road test it responds much better
Pilot jet seems ok as idling revs only climb up about 1 turn out
Need a proper ride to test it and do a plug chop test
Bike manual has standard pilot as a 15 so it may be better leaner but top end was also rich so more inclined to think needle or main jet was rich

 

[Kevin_TE250]

seriously thinking about running the needle on the second clip to lean it .. it's on the 3rd clip now... but I'm worried about blowing it up....

380 main
17.5 pilot

3000 to 7000 feet

 

[Kevin_TE250]

seriously thinking about running the needle on the second clip to lean it .. it's on the 3rd clip now... but I'm worried about blowing it up....

380 main
17.5 pilot

3000 to 7000 feet

My needle is has j8-60 so I'm assuming it's a 60 ? I also have a 58 and a 59.. so larger 60 is leaner ?

 

[rockdancer]

im no expert but the needle position doesnt affect wide open throttle too much - taper a tiny bit
Main jet mostly - refer "carburetor tuning" by Canadian Dave on web
So needle will not cause it too blow it up - try 2
I think larger is leaner - I d leave the 60

 

[Motosportz]

Correct, it is hard to blow up a bike by messing with the needle. near imposable. Feel free to play with it. The PWK is hands down a MUCH better carb than the Mikuni. I have had no need to pull the PWK since put it on with the right jetting. Rips from bottom to top, start better, pulls harder everywhere and gets slightly better fuel mileage. I played with my Mikuni for 6 months and could never get it to run as well and consistent as the PWK. Starts and runs pretty much perfect all the time now. I don't think about my carb any more.

- Someone on this forum posted about signal strength and how the PWK carb is designed better and draws fuel EZer down low. I think this is spot on. No matter what jets you run in the Mikuni it's never going to run as good as the PWK because of the design. IMHO.

 

[Kevin_TE250]

I know... I'm sold on a PWK....getting the funds together..... as far as your JD Kit, does it come with a jetting guide ? ya know what jets at what altitude and what needle ?

 

[BikeSDP]

as far as your JD Kit, does it come with a jetting guide ? ya know what jets at what altitude and what needle ?

What fun would that be?

I think someone near you may have the prescription in the jetting database.
Also, I've seen Kelly give folks jetting tips whether he sold the carb or not.

 

[dirt-dude]

Kevin, If your bike hesitates and takes a second or two to clean up
in a roll on and loads up at slow to moderate trail speeds its likely
the needle. I would probably go right to the top groove with your
altitude. In the heat of summer I run position #1 and when its
cooler I run #2 I'm using the j8-60 needle in my 04 125.

 

[Kevin_TE250]

Kevin, If your bike hesitates and takes a second or two to clean up
in a roll on and loads up at slow to moderate trail speeds its likely
the needle. I would probably go right to the top groove with your
altitude. In the heat of summer I run position #1 and when its
cooler I run #2 I'm using the j8-60 needle in my 04 125.

just put a 17.5 in tonight and the clip is in number 2.. Hopfully I get a chance to try it out this weekend....