81 Carbs

[Twobond]

Hello, rebuilt carbs in 81 750K did off bike leak test. no leaks. Installed carbs gas poured form top of #2 carb while cranking and once started. Took off checked. no leaks off bike. Installed and still pours from top of #2 carb while cranking and running. Is there a suction while running. I thought just gravity feed.
Walter Houston Texas

 

[mrtwowheel]

Do you still have the vacuum operated petcock on your bike? If so, do a search about it on this forum. Best thing to do about it is remove it, connect a fuel line directly to the carbs with a filter and plug the vacuum port on carb #2. I make a short plug with fuel line and a cut off stainless bolt that fits tight into the fuel line. Get rid of that SOB before you torch your bike. Also search SOS.

Edit......pretty sure you have a hole in the diaphragm of that SOB. This causes engine vacuum to pull fuel from the tank.

 

[Motogrady]

Mrtwowhl sounds like he’s on the right track.
CV carbs. Vacuum lifts the slides, not throttle cable.

 

[mrtwowheel]

Mrtwowhl sounds like he’s on the right track.
CV carbs. Vacuum lifts the slides, not throttle cable.

Every engine has vacuum??????????????????????????????????????????????????????????????????

 

[Motogrady]

The air sucking into the cylinders creates a vacuum.

The diaphragms are located under the domes on the top of the carburetors.

Very delicate they are.

 

[Motogrady]

They look like this.

 

[Walter]

Hello, rebuilt carbs in 81 750K did off bike leak test. no leaks. Installed carbs gas poured form top of #2 carb while cranking and once started. Took off checked. no leaks off bike. Installed and still pours from top of #2 carb while cranking and running. Is there a suction while running. I thought just gravity feed.
Walter Houston Texas

Thank you all for your feedback. Walter

 

[mrtwowheel]

They look like this.

That's a carburetor, not related to the OP's problem. Also the DOHC CV carbs have no diaphragms under the domes.

 

[Twobond]

anyone tell me what this is and where does it go?
Walter in Houston

 

[mrtwowheel]

anyone tell me what this is and where does it go?
Walter in Houston

Can you get a better picture with a quarter or ruler beside it for size reference? Very out of focus on my screen. Hard to tell if it is a hose or what from here, object on the end of it is very out of focus.

 

[mrtwowheel]

I put on my glasses........that seems to be your vent hose with a broken T connector. It goes between carb #2 and carb #3. If you take the tank off you should see two short rubber tubes, one on carb #2 and one on carb #3. The plastic barbs for that plastic T may be broken and still be inside of those two short hoses. After you verify that that is where it came from come back and we'll figure this out. Pictures help.

 

[mrtwowheel]

If those two short hoses are gone...........those are 6mm fuel line, nominal 1/4" fuel line, but 6mm is a tighter fit. So..........use the tightest 1/4" that you can find, it will actually be 6mm.

Edit........Orielly's works for me

 

[mrtwowheel]

Those rubber tubes are about 3/4" long

 

[Walter]

So, wher I have the clear hose is where this “T” connected gos

 

[mrtwowheel]

Yeah, that plastic T goes in there and the hose goes up over the airbox, there is a U shape on the right side of the bracket that holds the airbox for removing the carbs, the hose goes into that U shape to hold it, the hose continues to drape over the airbox, it hangs down to about the middle of the airbox and goes nowhere after that, no plug, just open to the world.

 

[mrtwowheel]

And the hose and middle barb of the T point UP.

 

[Walter]

leave this off and just turn the petcock off. Plug the vacuum port. Go. With gravity feed only

 

[mrtwowheel]

leave this off and just turn the petcock off. Plug the vacuum port. Go. With gravity feed only

Yeah, just like that. Be sure to use a filter or you'll be yanking those carbs off again. You may have to try different ways to route the supply hose and filter before you have good flow, a smaller dia. filter helps sometimes. Those vinyl port plugs at the box stores will just disappear, I use a piece of fuel line and plug it with a cut off stainless bolt, it stays even without clamps.

 

[mrtwowheel]

Congrats in advance. After removing and bypassing that vacuum operated petcock from hell, you have just done the best mod for these bikes. Safer and more reliable after doing that mod. These are GREAT bikes.

 

[Walter]

Thanks for your help! I agree great bikes. Walter