help with a mikuni flatslide carb needed

[JIMFROMTEXCO]

ok now i need some serious help here tuning wise :o according to the esr site i should be running 360- 400 main, a 25 pilot and the needle on the 3rd clip. first off how do i get the needle off the slide to set the clip. second i had a top end port job on my old cylinder now im on stock cylinder stock bore. it ran good with the old cylinder just didn't fit my needs. anyways my pilot is a 55 and my main is a 320. it starts up runs and just wants to die.. plugs come out looking black after opening it up letting it idle the plug looks wet not oily.. should i buy 150-160 main jet and a 25-30 pilot? the esr site jetting guide is for pipe and air box eliminator. please help me!!!

[mxduner]

Originally posted by JIMFROMTEXCO
ok now i need some serious help here tuning wise :o according to the esr site i should be running 360- 400 main, a 25 pilot and the needle on the 3rd clip. first off how do i get the needle off the slide to set the clip. second i had a top end port job on my old cylinder now im on stock cylinder stock bore. it ran good with the old cylinder just didn't fit my needs. anyways my pilot is a 55 and my main is a 320. it starts up runs and just wants to die.. plugs come out looking black after opening it up letting it idle the plug looks wet not oily.. should i buy 150-160 main jet and a 25-30 pilot? the esr site jetting guide is for pipe and air box eliminator. please help me!!!
remember, the mikuni jets are completely different than the keihin jets.you mentioned using a 55 pilot, in a mikuni thats way too fat

[Aceman]

Just an observation:

I notice that every time one of you Mikuni guys post a jetting question, nobody can answer it because they're jet sizes are so different and very few run those carbs.

A basic tuning guide can be had from Duncan racing, it's based on the pwk, so the basic tuning principles are there but some of the info might not match up to a Mikuni. I hope those carbs are worth the trouble...

[JIMFROMTEXCO]

i realize the jet differences, i was hoping somebody that runs a mikuni could chime in. going buy esr's website the specs i posted area baseline for pipe and no air box. i was shocked to see what my jet sizes were compared to that. im going to buy 25-30 pilot and maybe a 150-160 main and try to figure out the needle adjustments. if anyone can chime it i would really like that.

[mxracer97]

I have a Mikuni 38mm TMX carb on my ESR 310 motor with the following jetting specs:

25 pilot
air screw 1 1/2 to 2 turns out
6BEH1-73 needle with the clip in the third groove
420 main

Your pilot definitely seems too rich. The jetting specs you got from the ESR site looks like a good place to start, and Aceman's suggestion of looking at Duncan's jetting guide on their website is a good one. The guide will help you fine tune your jetting if necessary.

[JIMFROMTEXCO]

ehh! Now i'm really confused with the 320rd jet in the main, and the 55 in the pilot. my needle is on the 3rd clip from the top and the needle is a 6fj40. is there any way to determine if my carb is a tmx or not?

ithink im gonna but the jets like esr says and try them.

[JIMFROMTEXCO]

also note this is a 38mm carb

[mxracer97]

.
is there any way to determine if my carb is a tmx or not?

Yeah, my carb has "TMX" cast onto the side of the carb. If you take a look at the ESR website they have a picture of the TMX carb you can compare yours to.

[JIMFROMTEXCO]

mine dosn't have the tmx cast on the side but i moved the clip on the needle to the 2nd from top and it seems to run better.

[mxduner]

i have an esr 310, a 36mm tmx, and i run a 25 pilot and thats right on the money.

[mxracer97]

Based on the fact it doesn't have the "TMX" marked on the side and it has a 6FJ40 needle in it, I would guess that your carb is NOT a TMX, but probably a TM model. I would do a google search for this model of carburetor to try and find some jetting specs. I do not think the jetting specs on ESR's website will help you much as they are for the TMX series carbs.

[JIMFROMTEXCO]

damn i cant find any jetting specs. i just ripped it around my yard wide open the plug comes out black. the pilot seems ok once i adjusted the air screw. I'm gonna try a different clip setting and see if that cleans up my mid-range.

[machwon]

I used a 15-20 pilot, 5EJ12-55, 57 needle in the middle and 390-410 main, summer-winter specs. That was on a 38mm tmx with a small bell.

Keep in mind some mikuni carbs have needle jets to go with the jet needles. The TMX carbs don't have the needle jets they are a fixed size.