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TRX850 Fuel Tap

Posted: Tue May 26, 2020 4:54 pm
by Fastdags
I know I Know, I'm willing to bet that if this forum had a £ for every time this question gets asked the Moderators would be minted!

First things first. I just bought a '96 TRX850 and quite frankly I'm in love already. The Wife is not impressed believe me. Always had Japanese 4s up until now, so this is my first twin and boy what a difference. Serious amounts of fun and character.

On with the obvious and stupid question, the TRX850 Fuel Tap (on my bike anyhow) shows directly up = "RES", directly down = "ON" and halfway (facing directly rearwards) = "PR"

So, firstly do I ride with it in "ON" and then switch to "RES" when the spluttering starts? And what on earth is "PR".

Kind thanks in anticipation of being put right as a TRX850 Newbie :oops:

Re: TRX850 Fuel Tap

Posted: Tue May 26, 2020 7:29 pm
by PeteJ
Hiya dags, you are right on the first two but PRI means prime, as in the tap will let fuel flow without the engine running. The fuel tap works via vacuum in ON and RES settings, the only difference is that the ON setting sucks in fuel from a higher level in the tank than RES does. As you probably guessed, RES is reserve and it will let the remaining fuel in the tank out of the tank after it can't get any more from the ON position.
Like many others here, I switched the vacuum operated tap for a regular gravity feed version with only ON and OFF settings. I tried to find one with a RES as well but couldn't find one fast enough so stuck with this simpler model instead. So no reserve option for me then, I just gotta keep resetting the tripmeter when I refuel and remember to keep an eye on it.

Re: TRX850 Fuel Tap

Posted: Tue May 26, 2020 8:07 pm
by Fastdags
PeteJ wrote:Hiya dags, you are right on the first two but PRI means prime, as in the tap will let fuel flow without the engine running. The fuel tap works via vacuum in ON and RES settings, the only difference is that the ON setting sucks in fuel from a higher level in the tank than RES does. As you probably guessed, RES is reserve and it will let the remaining fuel in the tank out of the tank after it can't get any more from the ON position.
Like many others here, I switched the vacuum operated tap for a regular gravity feed version with only ON and OFF settings. I tried to find one with a RES as well but couldn't find one fast enough so stuck with this simpler model instead. So no reserve option for me then, I just gotta keep resetting the tripmeter when I refuel and remember to keep an eye on it.
Thanks PeteJ, really appreciate your reply. That's sorted it for me, so now understand much better what the settings mean etc.

Have likewise read horror stories about the stock Fuel Tap since being on the Forum, so my next job is definitely going to be to change out for a much simpler Fuel Tap. Do you have any recommendations of what Tap to fit? Which one did you go for?

Just come back in after an evening's ride in this beautiful weather we're having - it quite honestly doesn't get much better !

Thanks for your help and advice.

Regards dags.

Re: TRX850 Fuel Tap

Posted: Tue May 26, 2020 8:55 pm
by PeteJ
Well, as long as the bolt holes line up with the tanks, you could put any kind of tap you want in to replace the stock one. I went for an early model R1 tap because it was cheap and then rebuilt it with new seals to eliminate any risk of it leaking in use. Later I did find an aftermarket tap with a reserve option but the outlet pipe diameter was half that of the R1's tap. So I put that tap onto the shelf and just used one of the sieve filters from it to replace the R1 tap filter. A lot of older Yamaha taps will fit this tank so finding replacements is easy, just remember to block the old fuel tap vacuum hose if you do change the tap.

Re: TRX850 Fuel Tap

Posted: Wed May 27, 2020 12:01 am
by dicky