Yamaha TRX850 Enthusiasts Forum

Thanks dicky.

I will probably need to replace the manifold boots on the carbs as they are starting to crack.

I’m thinking I will give the air box a go first.

I tried posting a pic of my fuel tap to see if it was replaced already but the board can’t handle it. Do you mind if I pm you?

The stock tap is Res/Pri/On, no Off position, and has a vacuum line connected to it.
With no vacuum, ie engine off, the internal rubber diaphragm should block the flow of fuel in Res and On positions.
In Pri the diaphragm is bypassed so fuel can flow freely.
What actually happens is that the diaphragm always leaks and lets fuel flow out.
This is a pain if you take the tank off and fuel always dribbles out of the tap, but more so if you have leaky float bowl needles, because now fuel can flow out of the tank, through the carbs and into the cylinders. Next time you hit the starter button you get hydraulic lock. In the worst case you crack the heads and bend the crank. It happens.
So, ditch the tap for a cheap Res/Pri/On tap that eliminates this problem completely. Who cares if the float bowls weep a bit of fuel, as long as they can't keep on weeping all weekend.
Pretty much any aftermarket Yahama tap will fit, but the 5JJ is a tried and tested option. You simply replace the tap, remove the vacuum line from the inlet manifold and then block the port with a rubber bung.
Rinse, repeat, wipe hands on pants.