GT750 Fuel Tap - how does this work?

[Whit]

My GT750 does not get fuel from the tap in the ON position. Will only run in PRI or RES. I have taken it apart several times so I just figured I did not put in on correctly. Now that I look at it I really don't understand how it works in 3 positions.

I see four ports in which I will call North, East, South and West. When I put a straw on the North port and blow I feel air coming out of the 3 fuel lines. Therefore I believe this port must be uncovered by the tap to get fuel to the carbs.

Fuel will come out of the EAST port with engine off so I would assume this port must be uncovered by the tap when in PRI. That leads me to the conclusion the South and West must on ON and RES.

So since the tap can only uncover 2 ports in any position and can only be in 2 positions when North is uncovered I know that I don't understand how this works. Where am I going wrong with this?
Thanks,
Pat

[Coyote]

Is it possible you are suffering PO syndrome? To my memory, there is no west hole. Just a boss that one of the 4 hole gasket locates on. Sounds like someone has modified it for you.

[GT750Battleship]

Hi,the fuel tap should be a vacuum type in the on position,lever in straight position or NORTH,if you prefer, fuel only flows when the engine is running..engine stops...so does the fuel !! The same thing for reserve position...fuel will flow to the carbs in the prime position "all the time"..only use if carbs have been dismantled & are empty or if you suspect they maybe empty after standing for prolonged periods etc,important that you DON'T leave in the prime position as you run the risk of getting a crankcase full of fuel,then there is the very real threat of hydraulic lock which results in bent con rods (expensive) How many hoses are connected to you fuel tap ?
There should be two ? The one on the left is the vacuum hose..this is connected to the centre carb one end & to the tap at the other end.IS it there,& IS it connected to the carb OR maybe this hose is split OR there is a fault with the diaphragm rubber in the fuel tap ?
Cheers
Roger

[Whit]

The tap has 4 tubes, one for each carb and one for the vacuum. I can put a vacuum on it and get fuel in the reserve position only. The PRI is working correctly and pours out without a vacuum. The ON position is almost like an off. No fuel comes out even with a vacuum. //Pat

[GT750Battleship]

God knows what tap you have got there or what it's off
Looks like previous owner has "stuffed" things up ?
Definitely not off any Suzuki triple...Genuine Tap on Ebay USA for $110 Dollars,not cheap,but will work & be correct for the bike ? A photo would be good ?
Cheers,
Roger

[Barry S.]

It's a '73 with regular carbs, not CV carbs and one fuel line. Something messed up in the vacuum side not opening.

[Barry S.]

They are still available...........for $354 from Alpha Suzuki. Better work on that one.

[tz375]

Pull it apart carefully and see what's going on. The usual mode of failue is for the O ring to stop sealing and they weep. Yours sounds like a crack in the diaphragm or the pintle is stuck.

[Alan H]

The early triples (all of them - 380/550/750 - with separate carbs) had 4 ports on the fuel tap.
One to each carb and one to the vacuum connection on the inlet of one carb/engine connection.
PRI allows fuel to flow when (for instance) you haven't run the bike for some time and the carbs are empty.
ON for normal running but only when the engine is running.
RES for low fuel level in the tank (usually about a gallon or so), but only when the engine is running.
So if the carbs are empty, put the tap on PRI, start the bike, then put it on ON or RES depending on the amount of fuel in the tank.
DO NOT LEAVE THE TAP ON PRI WHEN THE ENGINE ISN'T RUNNING OR YOU HAVE THE CHANCE OF THE CARBS PASSING FUEL INTO THE CRANKCASES AND CAUSING A HYDRAULIC LOCK WHICH CAN CAUSE BENT CONRODS.
If you have a gallon or less in the tank, then ON won't flow fuel when the engine runs.
If the tank has more fuel in than that I would imagine that the fuel tap filter is bunged up (there are two filters on the tap, inside the tank).
To get to the filters, empty the tank (tap in PRI position) then remove the tank and lay it on its side (tap up) take the two 6mm bolts out and the tap should come away from the tank. You can then have a look at the filter stacks and clean them as necessary. I understand a tap/tank gasket from a GS750 fits and is cheaper!
Have a look at the diaphragm behind the large 'round' casting too and clean all the crud out of the tap and pipework. Might be a good idea to flush the tank out too in case there's some crap in the bottom. Use paraffin or diesel to flush the tank out, then when completely empty refill with petrol as normal.

[Alan H]

http://www.ebay.co.uk/itm/suzuki-380-55 ... 19efba85f7" onclick="window.open(this.href);return false;

Might be some good - especially at that price........