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Mikuni Jetting

Old 06-26-06, 06:52 PM
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Mikuni Jetting

I've got a 44mm mikuni on an aggressive street port 12a that was designed to start making power around 5,000 rpms. I'm running a Comp-70 fuel pump. Anybody who has experience with a similar set-up, can you give me some suggestions as to what kind of jetting I should go with? Unfortunately, I don't have enough money to buy a bunch of jets, so I need too start off somewhere close. Thanks
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Old 06-27-06, 07:55 AM
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For Solex/Mikuni 44PHH two barrel side draft carb, used on street ported 12A with header and free flowing exhaust:

Venturi 39 mm

Main fuel jet #200

Air Jet #240

Idle Jet #62.5

Accel. Pump #90

Emulsion Tube OA


Note: you must have exactly 39mm venturies for the above jet recommendations to work. I used this setup in the early '90s on my street driven, street ported 12A. I still have a few Solex/Mikuni jets available for $5 each + shipping. I don't know what sizes I have on hand until I inventory them, so if you want them send me an email at

[email protected] and put the words "Mikuni Jets" in the subject line
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Old 06-28-06, 02:34 PM
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Hmm. That seems kinda lean. When I say aggressive SP, I mean like, as big as you can get
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Old 06-28-06, 08:36 PM
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Maybe I am wrong on the air jet size; maybe it was a smaller. My notes from 1991 are smudged on the air jet size.

What jets and venturies do you have right now? Have you even driven your car with the Mikuni PHH carb?

My street port engine back then was pretty strong. I still use a street port 12A for a daily driver now; only now I use a Weber 48 IDA downdraft carb.

Last edited by speedturn; 06-28-06 at 08:40 PM.
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Old 06-29-06, 12:13 AM
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I ran it on my stockport, which I believe it was tuned for, but I have yet to run it on my current streetport. I'm not sure what the numbers are.

I've actually decided to just rebuild the carb with the current jets, test the A/F with a wideband, then choose jets accordingly.
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Old 07-03-06, 05:54 PM
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That is always a good plan. Every race engine is always a little different, and tuning with a good A/F ratio meter is the best way for good results.
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