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Author Topic: Carburetor size and fuel economy  (Read 461 times)

jedaks

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Carburetor size and fuel economy
« on: September 25, 2012, 02:09:01 PM »
Hello all
I'm considering upgrading my Mikcarb VM28, since I have an Ace Canister and a goldstar style exhaust. I have a question about how a larger carby will effect fuel useage.

Does a bigger carby use more fuel at any speed/RPM, simply because it is bigger? Or does it only really use more fuel at speeds/RPMs higher than the 28mm can currently manage? I hope that makes sense.

ace.cafe

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Re: Carburetor size and fuel economy
« Reply #1 on: September 25, 2012, 02:28:18 PM »
It depends on how good you are at jetting it, and your riding style.

The Fireball with the TM32 on it, in proper tune, gets 70mpg at 70mph in highway cruising. That's US gallons. In Imperial gallons, it would be 85mpg.

With more normal cylinder heads, you might expect somewhat less, perhaps around 60mpg. If you are very heavy with the throttle, it might be lower yet.

Home of the ACE Fireball 535 Bullet,  Ace GP Hi-Lift Roller Rocker Head . Pistons, cams, etc. Highest performance Bullet engine mods available .  AVL mods. Redditch 700/750 Twin mods. UCE kit soon.

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jedaks

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Re: Carburetor size and fuel economy
« Reply #2 on: September 25, 2012, 02:51:11 PM »
Thanks for such a quick reply.

Carburetor jetting..my nemesis. You have patiently helped me get my mikcarb in tune and I salute you.

I have things tuned just right at the moment and I'm enjoying my Bullet. The mikcarb is satisfactory for 90% of my uses. I don't generally ride fast or hard. Sometimes however, especially on long hills on the highway with trucks behind me, I have the throttle wide open and am doing 65mph. Having that little extra giddyup would be beneficial.

A set of your clubman cams wouldn't go astray either!

mustangdave

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Re: Carburetor size and fuel economy
« Reply #3 on: September 25, 2012, 10:29:54 PM »
Jedaks,

I run the VM28 rejetted...with the ACE canister and Goldie pipes...get 60-65mph...LOL...when the bike is in proper form...took Justin and I a couple of tries to get it properly jetted, but when it runs it runs REALLY nice.
I rode Japanese bikes as a kid...then I grew up and got some British Thunder