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 Topic: MC18 carbs - Air solenoid blocking (Matt - Tyga?) 







Matt@TYGA
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Matt@TYGA » Fri Apr 23, 2010 11:49 am

Waldo, don't mind Granty......he's missing the Happy times Wink

However, as he so rightly says, you'll have to suck it and see, as it's a little outside the norm.

What I've done before on an MC18 is not use the solenoids and fit main jets to the hoses. I'm not gonna get specific for fear of getting it mighty wrong as I haven't done the 16, and the 18 I did wasn't stock.

The MC21 I did was to replicate the F3 carbs. It seemed to work pretty well.

Steve and Andy (and others probably) will want to shoot me, but what I did was take a saw to a set of F3 carbs so that I could see and measure what was inside (orifices etc). From what I found it was quite simple to replicate.

Anyway, if you go this route, remember that the MC16 exhaust port is tiny, so bigger carbs without other mods may not be the way to go. But if you do, start by plugging the hoses with small jets, which will keep it rich (safe) and then adjust accordingly.

As a tip (not real numbers). Say you start with a #100 main jet plugging the hoses, this will give you a bench mark fuel flow. If you then increase to a #110 main jet then you will lean off the bottom end a little, but lean off the top end a lot.

If the engine feels good at the bottom but lean at the top, reduce the plugging jet size.

Good at bottom, rich at top, increase plugging jet size.

Lean at bottom, good at top, increase main jet, increase plugging jet.

Rich at bottom, good at top, reduce main jet, reduce plugging jet.

You're looking to get the fuel flow curve right with the plugging jets.

Feel free to post your finding and I'm sure there will be help and ideas offered.
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