Jetting Qs. (mukuni tmx 36mm)

[beobe99]

I know this Qs has been beatin to death but what the hell....

Hey guys how's it going.. I did search of course and spent way to much time looking over the service manual to try and figure this out on my own with no luck.

what I have

89 engine
Mukuni TMX 36mm
ESR trx-6 pipe (low to mid range)
K&N filter with air box cover removed
Boyseen TQ reeds
Reed spacer
all on a fresh rebuild.

Im on the East coast (Phila. PA area) and winters just about to begin.. I would prefer reliability over risky high HP.

I opened up the carb and cleaned it and wanted to pre-jet it for the intial start up. (I boughtthe carb used so no clue on the current jetting)

The qs. I have

1. how do I know what the jets size is? I see very small numbers on the jets themself but they are either 2 numbers or 3 and no where near the stock jetting or any other jet recomendations I've seen.

2. What would you guys recomend to TRY to get this right on the first shot.

3. Are there different air screw sizes? what ever ones in there I took out, cleaned and screwed all the way in then backed out 1 1/2 turns like the manual said to. Also bringing this screw further out or in adds more fuel?


Sorry if I come off ignorant to all this. This is my second R build and I lucked out with the first buying a engine, pipe, filter, carb combo and lucked out that it ran smooth. This new engine I just got done assembling the bottom end and top for the first time too (everything seems solid there.)

Any help would be great!!

Thanks guys

[beobe99]

one more qs. The higher the number on the jet the richer? or leaner?

[Rollscanardly]

first the higher the number the richer...and when you turn the air screw out it give's it more air(leans the mix). Mikuni's jets are a lot larger numbers than a Keihn carb because they are measured differently, and thats why the jetting appears to be so far off...i have no expierience jetting Mikuni carbs but you might try calling some place that sells them for 250cc engine's...maybe duncan or esr...


Hunter

[beobe99]

Thanks hunter. I checked with ESR and they of course sell the pipe i have and the exact carb I have. Ill try them tomorow and see what they say. There site has jetting specs (i was excited as hell) but they are only for 4-strokes for some reaosn. Hopefully they can help with a guess considering they are on the west and im east..

Thanks

[wilkin250r]

The stock carburetor is a Keihin. And many people are fond of running the 38PWK, which is also a Keihin carb.

As such, almost ANY jetting specs you are going to see are for a Keihin carb. This includes the manual, on here, and also the ESR website.

That's not to say the Mikuni is a bad brand, they are very good. But it DOES mean that you can't really make a jetting comparison between two brands. The circuits will perform differently. You can't go by somebody else's jetting specs in a completely different carburetor.

[beobe99]

Originally posted by wilkin250r
The stock carburetor is a Keihin. And many people are fond of running the 38PWK, which is also a Keihin carb.

As such, almost ANY jetting specs you are going to see are for a Keihin carb. This includes the manual, on here, and also the ESR website.

That's not to say the Mikuni is a bad brand, they are very good. But it DOES mean that you can't really make a jetting comparison between two brands. The circuits will perform differently. You can't go by somebody else's jetting specs in a completely different carburetor.

Thanks, Im hoping someone on here has the same carb as I do with a similiar set up to get me started here. Or advise.

[robyone]

I'm running a 38mm TMX with a .420 main and a 25 pilot on a stock cylinder ported for mid range at 67.50.

I would pick up a .380, and .420 mains....and 23 thru 27 pilots.
You should be able to dial it in from there.

[250r rider 88]

im running almost the exact same setup as you right now during break in im using the jets from ESR which are 460 main, 25 pilot, needle in middle position, once i had the idle adjusted she runs great, havent got into the top end so not sure if my main is to rich or not will report back, but i would see what jets you have and go from there, my set up is 36 mikuni esr trx 6 k and n with airbox lid, boyeson rad valve, low/mid port by Neil hope this helps as no one on here could really help me had to figure it out on my own but most people run the keihn so its no big deal :devil:

[beobe99]

robyone

250rrider88

Good stuff guys!!! It should deff give me a starting point no doubt..

I'll let you know if my sh** blows up hehe! and 250rrider88 let me know how it turns out for you and Ill do the same..

thanks