Fuel tap question

[Homer]

On the TRX I bought recently, (see "My new TRX" thread in Central Forum) the previous owner/builder had severely modified the tank. So much so that there is actually no fuel tap at all, just a spigot welded on the tank which allows fuel to flow constantly to the fuel pump. I've just fitted a tank off a Yamaha XJ6 which normally runs an electric fuel pump mounted on the underside of the tank. I've blanked off the hole, but have to fit a fuel pickup of some description.

My question is, do I need the original TRX fuel tap, and if so, why? I never did understand how and why the tap worked on my first TRX. Why can't I just use an ordinary fuel tap which simply turns the fuel on or off. Why does the TRX unit have a Prime setting, and why.

So many questions and so little beer.

Thanks in advance again.

[trixynut]

Standard tap has 3 settings: res which is reserve, pri which is prime and lets fuel flow freely to carbs to prime them (or used for draining tank) and on which is controlled by a diaphragm so wont flow fuel unless the pump sucks it out.
The trx has a fuel pump as the tank is lower than the carbs iirc.
A simple on/off could lead to carb flooding.
A simple on/off should work if the xj tank is higher than the carbs, but as said, they could flood.
An electric pump would work ok instead of the trx one.

[Mincehead]

Dave`s right, the TRX tap has a diaphragm to check fuel from flowing without a vacuum acting on it. Ie, when the motor is running.
You can stick to an on / off tap but always turn it off after you stop the bike or you are relying on the float needle valves stopping the bike from flooding herself.

[Homer]

Thanks Mince, Trixy. That was what I was thinking. I'll price up a new TRX unit tomorrow. If its too pricey I'll go with an On/Off unit, Shouldn't be a problem as I've always turned off the fuel on all my bikes when stopped. The way the builder set it up it was relying on the float valves not too flood. Not an ideal setup by a long shot.

[M.V.]

Thanks Mince, Trixy. That was what I was thinking. I'll price up a new TRX unit tomorrow. If its too pricey I'll go with an On/Off unit, Shouldn't be a problem as I've always turned off the fuel on all my bikes when stopped. The way the builder set it up it was relying on the float valves not too flood. Not an ideal setup by a long shot.

Last I checked they were around $160 AUD for the tap form Mr. Yamaha. I'd say that's too pricey for me.

[Homer]

Me too. Can get used from a wrecker for $55. Might go that way.