Mikuni VM26 Round Slide Jetting Equivalence?

[Wheelman-111]

Greetings:

Flash was running an OKO 26 with 46/122 jets. Pretty close to perfect there.

Never content with close, I have a Mikuni Old School VM26 on the way. Have a 35 Pilot and down and. 180-down mains. Any idea where to start?

[motormike]

I have no beneficial input, only this question;
Why not start with the same sizes that work so well in the OKO ?
Seems logical since diameters are the same....

[Wheelman-111]

Greetings:

Alas and alack; Mik and Keihin numbering systems are not the same. Flash 3 ran 165-180 Mains in the TM24, for example. OKO equivalents were in the 130-140 range.

[mousewheels]

Mik and Keihin numbering systems are not the same. Flash 3 ran 165-180 Mains in the TM24, for example. OKO equivalents were in the 130-140 range.

Right, they are different numbering systems. Getting input from someone running the Mik will be helpful. Yet your experience to run smaller for the Mikuni is backed up by the table below:


Secret jet chart link --> http://hondaspree.net/wiki/index.php5?title=Carb_Jets#
Only reason I have not yet published to the main wiki is to run spot checks sometime... Wheelman-111 testing counts!

[LMH]

What a wonderful chart you made!

[Red Eft Performance]

Not only is the numbering system different the vm carb has a round slide vs the flat slide of the oko. So that changes things as well.

[Wheelman-111]

Greetings:

Seems to me the Mik takes bigger, not smaller numbered Mains.
Here's the VM installed:

Mik26Install[1].jpg (111.87 KiB) Viewed 6498 times

Started with my biggest pilot, a 35, and a 160 Main. It started & ran, just not too well. Almost rideable with fat needle at full rich.
Put in 40/155, idled well but ran worse. Hard to "jump the gap" off idle. Lost RPM unless I opened the throttle gradually and tickled it. Moving the needle didn't seem to do much. Temps stayed way cool I'm thinkin it's rich all over. Ran out of time.

[mousewheels]

Seems to me the Mik takes bigger, not smaller numbered Mains.

That's because you have a 26" Mikuni - it won't fit my monitor
I remember Mikuni jets had two calibrations like RedEft posted, wonder if that's what's up?

Wheelman's pic rescaled to 50% then cropped...

Mik26Install_sm.jpg (135.76 KiB) Viewed 6512 times

[Wheelman-111]

Greetings:

Thanks to always-helpful Mouse.
I'm really starting from square 1. Nobody but Nobody has ever installed a VM near as I can tell, not even TreatLand customers despite $85 price for Legendary Mikuni Quality,

Bad news: its pretty big physically, maybe 1.5 oz heavier than the OKO 26.
Good News: no screws to lift the slide and change needle clip position. Just spin off the cap.
Bad news: 4 screws to drop the bowl, but at least it lifts straight off.
More Bad: I have absolutely NO idea where to start jetting this thing.

Somebodycan post that link to a step-by-step carb jetting tutorial?

[dun rite]

this one? http://enigma.lhosting.info/carbtune.html

[Wheelman-111]

Greetings:

Dat Be Da One, Thanks Dun!
I'll be sorting out the Pilot Sunday and Monday. Evidently worse going from 35 to 40 - needing at least 2 turns out on the air screw to idle - so I put the 32.5 in and see if it takes throttle without nearly stalling - BWAAaaaaaaa.

Where's The Bear when we need him?

Fixed that wacky pic. Snug fit.

[Wheelman-111]

Greetings:

This has turned out to be a Tuning Saga. Testing 32.5 Pilot with stupid-big Main tonight. I just need to get it ride-able so I can move on to testing to find the optimal Main. Working in the da'k ovah heah.

[Wheelman-111]

Greetings:

Illustrating the size difference between the Mik and my OKO, both 26mms. Mikuni can hold almost half a fuel tank's worth of gas in its bowl...

4OKO26+VM26.jpg (194.07 KiB) Viewed 6470 times

The Mik's fuel inlet barb is a full 1/4-Inch.
Cool Float mechanism:

MikVM26FloatSystem.jpg (172.15 KiB) Viewed 6470 times

The floats are mounted to those posts. They push up on the U-Shaped brass pivot to close the needle. Only issue may be if the needle gets "sticky"; Unlike the OKO, the needle isn't clipped to the float pivot and relies upon gravity alone to open. The Folklore of tapping on the carb if it won't start may have its basis here.
Popping the cap off to change the slide needle needs no tools.

MikVM26.jpg (135.2 KiB) Viewed 6470 times

Throttle cable took up all the slack I could generate, and the smaller spigot needs a different Treats donut. Not quite a Hermetic fit like it is on the OKO, which needs some persuasion to POP on. Otherwise, pretty easy to adapt to Flash's Engine Bay.

[fastplastic]

In my experience from oko to my round slide kehin its night and day everything seems to be designed to benefit the user and preform well also good luck and happy trails

[Wheelman-111]

Greetings:

Thanks for the encouragment, FastPlastic. I could use some right now. I couldnT get it even moving with 32.5 pilot/165 Main and ran out of daylight. Symptoms were contradicting Rich/Lean. ANY hint whatsoever, even just telling me your jet setup in your application, would help. A LOT.