Need help with Virago carbs

[fjrjonesing]

This, on my son's 86 Virago. It sat up before he bought it. I went through the carbs, soaked, then kitted both with K&L kits. Started right up but was leaking gas into the crankcase. Put a stopcock in the fuel line, replaced the needles and seats with ones from Mikuni ($65 a pop!), and bench tested it. Seats were holding. Floats were operating properly.

Starts and runs smoothly, but the aft header is getting seriously hot (blue-ing), the fore header is cool to the touch.

Both bowls have fuel. Both plugs are firing but are black. Gotta be gas getting blown into the exhaust and combusting, right?

Appreciate any help...

Jim/jonesing

 

[FJRMGM]

no problem - I load up with carbs quite often.

 

[charismaticmegafauna]

....was leaking gas into the crankcase. Put a stopcock in the fuel line,Appreciate any help...

You shouldn't need a stopcock in the fuel line if the stock petcock is operating properly. Is it a vacuum operated 'automatic' petcock? If so, and you think everything else is ok, it may be fuel leaking through the rubber diaphragm in the petcock and into the intake?

Does it start without the choke when cold? It shouldn't.

Just a couple thoughts -- long distance diagnosis ain't easy.....

 

[JasonB]

Did you remove and clean the jets, specifically the pilot or (low flow idel) jet? The vacuum passages for the low pass fuel system easily gets clogged. Secondly you might have the pilot (idol) jets set wrong. Sometimes counting the turn settings prior to removing can give bad results due to dirty or blocked passages. Try resetting to 1 – 1 ½ turns out from dead stop.

Just a couple thoughts, I am not an expert or familiar with the carbs on a virago.

Good Luck

 

[FJRay]

Some of those used a vacuum operated fuel pump. If there is a problem with the vacuum diaphram it will suck fuel in through the hose and raise hell with fuel delivery. It will run without the fuel pump as long as you keep the fuel level above the carbs. You can disconnect and plug the vacuum hose and run it to see if that solves the problem. Those pumps are a catalog item.

 

[JasonB]

Forgot this earlier. Black plug = rich fuel mixture

Lean it out. Typ. turn in the A/F mixture screws or pilot jets.

 

[fjrjonesing]

....was leaking gas into the crankcase. Put a stopcock in the fuel line,Appreciate any help...

You shouldn't need a stopcock in the fuel line if the stock petcock is operating properly. Is it a vacuum operated 'automatic' petcock? If so, and you think everything else is ok, it may be fuel leaking through the rubber diaphragm in the petcock and into the intake?

Does it start without the choke when cold? It shouldn't.

Just a couple thoughts -- long distance diagnosis ain't easy.....

You're right. I shouldn't need it, but I did. My understanding is that this is a typical Virago deal. (The "fix" is a Kawasaki petcock.)

The petcock doesn't use vacuum, and leaked even after being re-kitted. So, I stuck the stopcock in line. Problem solved.

Jason, I cleaned all the passages thoroughly. I owned a used XS1100 for 5 years so this is not my first carb rodeo. I really think that it is something like FJRay suggests: fuel delivery. Gas is overflowing the bowl and running into the exhaust. Can't figure it other than needles, seats, and floats, and those are all working.

Thanks for the suggestions though.

Jim

 

[ROADHAZARD]

have you checked the float height ?