Author Topic: jetting at bonneville  (Read 6709 times)

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Offline kiwi belly tank

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Re: jetting at bonneville
« Reply #15 on: July 12, 2015, 07:25:40 PM »
Growing up in a place where SU's were pretty much everywhere we used to hang them on everything, I even had 8 on a flathead at one time but never without a float bowl. I hope it works out for you on the salt & you don't burn it down. Golden rule, start out fat.
  Sid.

Offline wobblywalrus

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Re: jetting at bonneville
« Reply #16 on: July 12, 2015, 09:54:59 PM »
You can get a constant fuel pressure with a gravity fed system with an intermediate tank between the fuel tank and the carb.  My recollection is this system was used on the AJS porcupine.  Maybe someone over there knows the details.  My recollection is about the concept.   

Offline dresda

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Re: jetting at bonneville
« Reply #17 on: July 12, 2015, 10:22:03 PM »
I don't have a problem with fuel pressure just need to know a % of who lean to go. The reason we don't use float bowl on the SU is because you can't get Methanol needle valves for it.

Offline Milwaukee Midget

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Re: jetting at bonneville
« Reply #18 on: July 13, 2015, 12:25:30 AM »
Growing up in a place where SU's were pretty much everywhere we used to hang them on everything

HS4s make pretty Christmas tree decorations . . .

But seriously, I'm confused as to how you're going to maintain any tune consistency without floats.  I realize that methanol will require more fuel than a stock float set-up might provide, but even with an intermediate tank, if the tanks gets warm and pressure builds, you could be rich in the heat of the afternoon, and then suddenly lean a mile down the course.

There are enough variables to compensate for with varying adjusted altitude - and the carb will compensate somewhat for that - but for what will likely be inconsistent fuel pressure for 3 or more miles with no effective measure to moderate it sounds . . . well, kinda scary to me.

It may work on drag bikes in Great Britain, but the distance is shorter, and the temps are cooler.

For Bonneville, I think you'd want to be looking at what road racing bikes are using, not drag bikes.
"Problems are almost always a sign of progress."  Harold Bettes
Well, I guess we're making a LOT of progress . . .  :roll:

Offline manta22

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Re: jetting at bonneville
« Reply #19 on: July 13, 2015, 11:14:30 AM »
It seems to me that without a float bowl to keep the fuel at a constant level relative to the jets, the air velocity won't be creating a low pressure venturi to suck the proper amount of fuel into the air stream. Using a pressurized fuel supply without the float bowl assembly seems to be converting it to a low-pressure fuel injection system. Does this sound plausible?

Regards, Neil  Tucson, AZ
Regards, Neil  Tucson, AZ