Petcock Locating

[Fry]

Does the Stk. un-modified Fuel Valve have to be mounted below the tank but above the Carb Inlet?

Can the Valve be located below the tank and slightly below the Carb inlet?

Can someone please explain again why Vacum is supplied to the Petcock?

Do Line Lengths matter?

Would it be easier to use a Motocross Valve to simplify mounting? The standard location is not an option.


Would it be better to mount it in some fashion to the Gray Mesh or hanging from the Black Mesh in this picture?

[nastynate6695]

i say junk the petcock and just get a three way selector.  on off and reserve.  then reroute your lines so they work install an inline fuel filter and be done..Thats what a lot of people have done.   

[Fry]

So go with the CRF like mentionoed in some of the posts?

But does it have to be below the tank, above the carb inlet?

[scottpA_GS]

seems like it shouldnt matter where the shutoff is? as long as the tank is above the carbs  It may create a bubble in the line or something though 

[the mole]

Does the Stk. un-modified Fuel Valve have to be mounted below the tank but above the Carb Inlet?

Can the Valve be located below the tank and below the Carb inlet?

Can someone please explain again why Vacum is supplied to the Petcock?

Do Line Lengths matter?

Would it be easier to use a Motocross Valve to simplify mounting? The standard location is not an option.

Would it be better to mount it in some fashion to the Gray Mesh or hanging from the Black Mesh in this picture?

To answer your questions, the vacuum hose provides suction to the diaphragm in the petcock so that the fuel supply is automatically turned on when the engine runs. if you modify the fuel system, I can't see any problem with having your new petcock slightly below the carbs. As long as the tank is above the carbs, gravity will get the fuel there!

In the old days, bikes had a fuel tap(petcock) that fixed to the bottom of the tank and had 'On', 'Off' and 'Res' positions. If 'Off' no fuel came through. Normal running was on 'On'. You had to remember to turn the tap on before you started up, and off after you stopped although leaving it on was not an issue if the carb needle/seat was in good condition. If it wasn't, then you had a fuel leak. (But you could see there was a problem and fix it). I rode with this system for 30+ years and it was simple and no hassle.

Now we don't have to remember to turn the fuel on and off, but we have two petcocks, a diaphragm or two, a vacuum line and a bunch more problems judging by the number of threads here on petcocks! I guess that's what we call progress

My near new bike is working fine, but the second I have trouble with the petcock I'm modifying it to lose the vacuum system. Apart from anything else, if you get a leak in the vacuum hose and that cylinder runs lean you could do very expensive engine damage.