Mikuni Jet questions

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skeeveman

New Member
#1
#1
I've got a 24mm Mikuni on my 6.5 clone. It came with a 90 main jet.

First off, I've read that mikuni uses a different jet numbering system. Can anybody produce a chart of common mikuni jet sizes with their respective orifice diameter? Or, if not, can somebody tell me the formula?


Next, can somebody tell me where I can just buy a handful of main jets, or maybe even a jet kit for them.

And finally, other than the low mixture screw on the bottom of the carb, the mid range adjustable mixture needle inside the throat of the carb, and the main jet inside of the bowl under the float, is there any other jets or tunable aspects I am not seeing on this carb? I'm ready to tinker.

Thanks in advance.
Jake
 
125ccCrazy

125ccCrazy

Well-Known Member
#2
#2
The taper bores like you have use regular Mikuni style jets, the jets usually go up in incriments of 2.5 so if you have a 90 you can go 92.5, 95, 97.5, 100 ect... or smaller if the 90 is too much... The air mix is the bottom screw up inside the tube, then the idle mix on the side, needle and main jet.. There is also the pilot jet but I'm not sure how available those are or if standard Mikuni will fit, the needle is odd, no numbers so finding different needles is a trick...

You can get jets at most any cycle, dirtbike or atv shop or off ebay...
 
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skeeveman

New Member
#3
#3
Thanks for the reply.

Yep, I knew about those other places to tune with, I've been playing with those already. Where is the pilot jet located?

Also, like I was asking in my starting post, do you know how to convert the jet sizes into thousandths (jet orifice diameter)? I've read they are not sized like standard jets. I guess could go verify this myself out in the shop by comparing it to other jets I have, but I thought I'd try just asking here first.

Could everybody with 22 and 24mm mikunis on 6.5 clones post up what jet they are using? Also include which carb they have, and what mods are done on the motor (such as header, what air filter, what intake, valve springs, which cam, etc), and if you can, what your elevation is, it would be very appreciated. This could turn into a very valuable thread if we get enough data gathered up.
 
npatton19

npatton19

New Member
#4
#4
Im running a 125 main, 12.5 pilot and havent had a chance to fool around with the needle yet. The 125 main gave me a good plug reading and the 12.5 gave me better acceleration over the stock, our jetting might not be the same but this is what has worked for me.
 
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skeeveman

New Member
#5
#5
Thanks for the reply, it's useful info.

Well, I still haven't found the drill to jet conversion chart for mikuni's, or an affordable jet kit. But, I have found a useful image that shows the metering circuit vs throttle openings.

Like I said, let's make this a very useful technical thread for mikuni users on 6.5's.

 
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skeeveman

New Member
#6
#6
And another I think this may be the chart I'm looking for, though I'd like a better one. If the image don't work, let me know and I'll host it on photobucket, the hosting site has some security ticket issues (expired).

I can't confirm if this is indeed for mikuni jets or not, but it appears to be from what I've goatherd about them going in 2.5 numerical steps at a time. If somebody can confirm this chart it would be great.

 
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slow5oh

New Member
#7
#7
skeeveman said:
And another I think this may be the chart I'm looking for, though I'd like a better one. If the image don't work, let me know and I'll host it on photobucket, the hosting site has some security ticket issues (expired).

I can't confirm if this is indeed for mikuni jets or not, but it appears to be from what I've goatherd about them going in 2.5 numerical steps at a time. If somebody can confirm this chart it would be great.

Click to expand...
it aint workin, host it on photobucket bitch.
 
typeone

typeone

Member
#11
#11
i havent messed with my carb this season yet but i believe i'm running the following jetting in my Mikuni 22mm w/a pulsed adaptor:

- 140 Main
- 12.5 Pilot
- Needle middle position (this is the one I cant remember)

The motor is basically a Stage 2 blue clone from AGK (without the cam), 14cc head, 18lb springs, RLV header, UNI filter. Runs fantastic. Idles great, winds out smooth. I order all my jets through AGK. tried a 120, 130 and 140 but the temps were dropping last fall. my need to tune with the warm weather coming but a test rip the other day felt great. the 140 main worked great up top, so much so that i now need new springs in my TAV2 to get a little more top-end speed. Running a 55T rear sprocket as well.

That tuning guide on the AGK site is what I kept handy while messing with the jetting, great resource.
 
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