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Offline thomasp48

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Why no petcocks on fuel-injected motorcycles?
« on: March 31, 2015, 06:09:18 pm »
Having the engine stop running and then start after switcing a petcock to reserve was an unmistakeable sign that it was time to start looking for a gas station. Fuel gauge and low-level warning lights are the rule with fuel-injected engines. What are the dire consequences that prompted manufacturers to switch from petcocks to keep users from allowing their engines to run dry. It might be as reasonable to ask why automobiles, with at least one exception, have used fuel gauges, even when their engines were carbureted, as all of ours once were. One suggestion is that contaminants settled to the bottom of the fuel tank will damage injectors. How is that worse than having them pass through carburetor jets? Is that the reason, or does it have something to do with possible damage to the fuel pump, or maybe both?

Offline gwcrim

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Re: Why no petcocks on fuel-injected motorcycles?
« Reply #1 on: March 31, 2015, 06:55:27 pm »
Motorcycles use gravity to feed fuel to the carb.  If the needle valve leaks and the petcock is left on you'll have a puddle at least or a severely flooded engine at worst or even a fire.  Cars use a fuel pump.  That eliminates the risk of carb leakage because there is no pressure when the engine isn't running. The fuel pumps in a motorcycle tank act as a shut off valve when the engine isn't running.

I agree that a petcock is nice for offering a reserve amount of fuel but they're kind of obsolete with fuel injection.
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Offline w8d4it

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Re: Why no petcocks on fuel-injected motorcycles?
« Reply #2 on: March 31, 2015, 07:04:15 pm »
I can think of two other factors right off. 1) fuel pumps are cooled by the gas running through them.  running them dry can't be helpful.  2) although I've never run a fuel injected motorcycle dry I do know that a fuel injected car that has been run completely dry can be hard to start. 
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Offline Coconut

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Re: Why no petcocks on fuel-injected motorcycles?
« Reply #3 on: March 31, 2015, 07:34:56 pm »
Then there's the shape of the tank - Petcocks are usually istalled in the lowest part of the tank,
and as has been mentioned are gravity fed, and don't have a fuel pump.

Have you seen the shape of the Trophy Fuel Tank ?

You need a pump to suck the fuel out of the different sections,
and pump it to wherever on the tankthe Petcock was fitted,
and the Petcock would have to be capable of withstanding the pump pressure  :087:



 

Offline thomasp48

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Re: Why no petcocks on fuel-injected motorcycles?
« Reply #4 on: March 31, 2015, 07:45:01 pm »
So that's how they keep the weight low and maintain a large fuel supply. Part of the tank is under the seat. I had no idea.

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Re: Why no petcocks on fuel-injected motorcycles?
« Reply #5 on: March 31, 2015, 08:03:33 pm »
Had a total loss house fire at 2:30 am in Houston once, and the insurance company's investigator traced it to a failed relay on the car which was later verified by a lab.  Funny how much you can discover with deep enough pockets to get some testing done.  Anyway, when I questioned his suspicions he informed me that there are failed relays all over vehicles all the time, and he even investigated one on a Corvette that had kept the fuel pump running after it was shut off and forced fuel through one of the injectors, filled a cylinder, crankcase, ran fuel out on the floor of the garage where there was a gas water heater, and at 2 am, BOOM, house went up.  A doctors house, and Chevrolet ended up paying big bucks, fortunately no one injured from it.  My garages have smoke alarms now, but didn't in the past.

Sorry for the hijack, if the moderator would care to move or delete this as unrelated, please do so.
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Re: Why no petcocks on fuel-injected motorcycles?
« Reply #6 on: March 31, 2015, 08:08:36 pm »
if the moderator would care to move or delete this as unrelated, please do so.

Looks OK and related to the topic to me !

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