Yamaha TRX850 Enthusiasts Forum

My petcock appears to have 3 positions.

I think they are On, Off and Prime.

I've always got mine set on the Prime position, so I was wondering if anybody knows what it means.

I've heard of On and Reserve, but what is Prime?

throttle wrote:My petcock appears to have 3 positions.

I think they are On, Off and Prime.

I've always got mine set on the Prime position, so I was wondering if anybody knows what it means.

I've heard of On and Reserve, but what is Prime?

You got on, reserve and prime....with prime you flood gas into the carbs (don´t need fuelpump).
I use it when i missed to quickly switch to reserve...otherwise it takes a while to start the tractor!

Thanks for the info. I've had it in Prime mode for almost a year now. I guess I should change it to On.

BTW, anybody know how far the bike can go after it you need to switch it to Reserve?

Hi throttle,

a further advantage of keeping it in the ON position is, you have a reserve!
Because, in PRI position you don't ...

Depending of course on the riding style, with reserve you should be able to do about 50 km (as far as my memory doesn't let me down).

my petcock has way more positions than 3,oh you meant..................

You guys have pet cocks? Do they do tricks??

Sorry, I'll shut up now!

You shouldn't leave it in prime. If you have a leaky needle valve in the carb then you could fill the float chamber of the carb with fuel and potentially pour fuel all over the floor. Also there may be a chance that you could pour fuel into the combustion chamber which could lead to all sorts of expensive consequences.

Plus of course in the prime position, if you take the tank off then fuel will flow out all over your boots. It shouldn't if you leave it in the 'On' or 'Res' positions.