Yamaha TRX850 Enthusiasts Forum

Hi all,
Was just wondering what needs to be done to delete the vaccum setup and install a gravity petcock?

I have already bought the new petcock and was just wondering what needs to be blocked off on the carbs, i.e vaccum lines.

Is it as simple as running a fuel line from the new tap straight to the t-piece on the back of the carbs?

Thanks in advance

A gravity fuel supply will work until the fuel in the tank drops down to the level of the carbs, then it will need a pump. The function of the vacuum pump is to lift the fuel UP to the carbs from the bottom portion of the fuel tank.

Rip out the old tap and replace it. Smash it to bits with a hammer and then set fire to it, just to be sure no-one else will ever use it.
Keep the fuel line running via the pump, you need it to get all the fuel out of the tank. The pump has not been a problem (so far).
Block the vacuum line that was connected to the tap, it should be connected to the LHS inlet manifold, but you might want to double check in case it has been swapped around.
The fuel pump runs from the RHS manifold.

Just a question, does many Yamaha motorcycles use same mounting to the fuel tap as on the TRX? Witch tap will fit?
Interested in same modification

keny72 wrote:Just a question, does many Yamaha motorcycles use same mounting to the fuel tap as on the TRX? Witch tap will fit?
Interested in same modification

It's a standard 34 mm fit. Almost every Yamaha use it, from WR's to R1's. Using a 1:st gen R1 tap is popular, and if you do a cross check, that one is used on a lot of other bikes as well. I'm using a cheap copy that I think was specced for WR400 or some such...