Hi all,

Im building a bike and need some downdraft carbs, does anyone know all of the differences between MC21 TA carbs and MC28 TB carbs?

I know they are both 32mm downdraft.

Has anyone successfully bored out MC18 or MC21 or 28 carbs?

Cheers
Jared

rick porter here in nz said he bored his carbs out to 34mm on his mc21

Difference? They are completely different. The needles and main jets *may* be interchangeable, but everything else is different. I would bet that the 28 carbs are *easier* to overbore since the bore is round, while the 21 carbs are an offset kind of oval bore. Even then, the needle-jet on the 28 is non-removeable so you cant get a boring device to go through without hitting it.
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Paul Herr
'88 FZR4/GSXR/YZF Frankenbike
MY BIKE PICS

Thanks.

We will be running a vortex electronic ignition that will talk to the tps and power-jets, so the mc28 carbs may be the go.

As for boring out the carbs, we can possibly bore up to the needle-jet from each side and then hand finish the rest.

What about the mc28's pgm system which apparently "opens solenoids at appropriate times which in turn control specific air passages into the carbs"(quoting a magazine article here).

Anyone got more info on this carb set-up for MC28's?

Cheers
Jared

Hey guys

what about NSR250SP's what carbs to they have?

Cheers
Jared
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If all else fails - gas it!