'87 vfr700 fuel pump help PLEASE

Well to reiterate, I ran a 1000cc '88 CBR1000F for as long as I owned it with the fuel pump discarded and running gravity feed. I don't think I'd go racing with it like that and I was commuting so I wasn't running it to the redline all the time, but it ran just fine. So a 750 should do OK too.

 

Not that I'm disputing the fact on a 750, but how much is supposition and how much is actual fact ? If a couple of guys said they have tried it themselves and it didn't work, then that's good enough for me.

 

Norcal- you sure you have taken a fluids class or really understand fluid dynamics? A tank on top of a refrigerator 6 foot high would have more static head than a tank only 1 foot off the ground with lines attached. Also if you add dynamic pressure in to either one of these tanks you would have more pressure, period.

Bernoulli's equation- look it up.

 

That is not what I meant.
If you have fuel injection, you have to have a fuel pump.
If you have carbs you do not need a fuel pump as long as the gas tank will feed the carbs.
Some bikes will need a crossover line between the two sides, depending on the design of the gas tank. Read that TWICE.
All gravity feed bikes have fuel filters.

 

Not the stock gas tank. Right.
I have two 1/4 petcocks on each side feeding one 3/8 line to the carbs. With a filter.

 

Yes I did look that up and as a former jet engine mechanic I understand some of those principals.
But he is refering to inviscable fluids at mach speed.

Anyway this is just a gas tank on a motorcycle. If the gas tank is above the engine and there is a petcock on each side it should work.
And I like to keep things simple. Why add a fuel pump if you do not need one.

 

Sounds reasonable to me.

But I would still want to know WHY it did not work. For instance would it work if the fuel tank had a crossover line and another petcock?
But do not add a petcock to a gas tank if you do not know how or do not have the skills.
NEVER weld on a fuel tank even if you washed it out.

 

Yes I understand. I did not know other owners of that same bike had already tried to eliminate the fuel pump. Everybody should just calm down. We are all just trying to help.

 

Tink, sound reasoning for sure - though I do wonder why Honda used a fuel pump on the '84 & '85 VF500F when it is not needed.

 

Kawasaki did that also in 2004 when they changed to fuel injection from carbs.
They still retained fuel pumps from an earlier attempt from fuel injection that was a failure, and then tried again in late 2004. So they could use the same wiring harness.
But they wanted to have fuel pumps because they could use a mercury switch to automatically shut off the fuel via the fuel pump relay. In the event the bike was in a crash.
With manual petcocks that was not possible.
My feeling is that if the accident is so violent that the fuel tank splits open all those fancy switches won't do much good.
The fuel can get ignited by the hot exhaust pipes, even if the ignition is off.

 

hallelujah....the mr. gasket pump had a fitting that was too small for my fuel lines. i needed a 3/4 inch fitting so i returned it and went to napa auto parts and got another fuel pump ($51) that was 3-5 psi with two 90° fittings($11). the pump works and the bike it back to purring like a loin. thanks for all the help. now i need to jack up the bike and put my pirelli sport demons tires on now....i can't wait to hit the mountains again

 

Wish you could have posted a photo of the fuel pump just to help your fellow VFR'ers.

Anyway on to the tires!