Just wondering if it would solve the syphoning problem when the key is off.

It's a bear trying to turn the fuel off on my AC650. they put the stupid valve up and under a fairing.

I was thinking of solving it 2 ways:
1) Replace the stock check valve going to the carbs with a stiffer one. My only concern is if the valve is too stiff, then it could reduce the fuel pump life. I'm wondering if it's weak so you can pull start the machine with no electrical -- so no fuel pump??????
2) Mount a 1/8" normally closed fuel solenoid across the shut off valve (they're sold for all the NOS setups). That way, you'd leave the fuel in the "off" position all the time. The solenoid would open with the key on, and close when the key off. Should you loose power, you could just turn the fuel to "on" to start it with no electical. Only downfall is the solenoid is a little pricey ($60US range).

 

Hmm, I am not aware of a check valve between the tank and the carbs on the P650. There is a check valve in the tank breather line. Some of us have had to remove it. Some have sent the breather hose up to the handelbars with the other hoses. Others just replace the check valve with a small fuel filter (keeps mud out but lets air thru).

 

It's on the Kawi parts page:
P/N: 49116-1126

AC P/N: 3201-055

It mounts just before the "t" that feeds the carbs. Reason I'm wondering is ever since I got my AC650, I've been pretty discouraged about how hard it was to start. You could crank for an eon before it would fire. I did some searching, and the Prairie guys were talking about syphoning fuel from the tank.

I started turning off the tank valve when stopping (but like I said, it's not that easy to get at), and what a night/day difference! It fires right up now, no problems at all. It's just awkward trying to reach up and flip it. To verify it, I ran it, shut it off, came back a couple of hours later (without cranking it), and pulled the plugs. They were soaked!!!!!!

I know ALL manufacturers "SAY" you have to turn the fuel off when you park, but I've never did that on any other machine I've ridden in the past.

Just glad that I know what makes it happen.....

 

That is a good question. The diagram calls the part a "valve assembly". I wonder what it does? BTW - I removed the check valve at the top of the fuel tank, it did help the flooding problem. Not a complete cure, but better.

 

Yup, there is a valve there. I can't why it would be a check valve, but if it is a spring loaded check valve it could be acting as a pressure regulator to prevent fuel from flowing it the pump isn't on. Unfortunately gas flows when pressure is in the tank.

That solenoid idea you have is a dang good idea. I would probably mess with the tank vent and see if that worked first, if not I would get that solenoid and put the problem completely to bed.

 

I am a little confused though. Shouldn't the floats in the carb rise and seal the bowl valve when the fuel bowl fills up? That's how every other carb I've ever played with works. If so, how does it flood? Does the engine tend to suck fuel out of the carb, and then it syphons back in from the tank? If that's the case, the solenoid would be the best fix.

I love this power plant, but the "choke" and this syphoning thing really baffles me!

 

I got you on H.L. ... but IMO, the gas tank can build up enough pressure ( from the heat of your engine, after a short ride, or from inside storage, etc )... the pressure relief valveon the Kawi tanks is very restrictive, & if the tank builds up enough pressure, rapidly enough, it will force it past the seats... I also use a very fine inline filter, to eliminate any particals in the gas, & always run a product like Stabil, to eliminate any gumming or varnish build up on the seats... no problems ever for me, & I have never shut off my gas...

 

Thanks for the tip.

 

Turns out the fuel breather is a really stupid design. Behind the tail light is a little breather box. One one side is a check valve. The valve lets air into the tank (to prevent a vacuum), but doesn't let vapor pressure out. After you stop, tank pressure builds and forces gas past the carb seats and floods the engine.

Removed the check valve and the problem disappeared. Woo Woo! I was getting tired reaching up under the fairing to turn off the fuel.

 

Glad to help... man... happy wheelin...