Oh great, another issue with my bike...

[JimmyR]

So I have the carbs (I think) pretty much sorted on my '82 GS1100G. It mostly runs, and when warm runs pretty well. I have done the tappets, sorted the timing and have new ignition, stator and plugs. I have both bench synched and vacuum gauge synched the carbies. Carbies are scrupulously clean and I have rebuilt them a few times now, checking that all the parts are the right value. Exhaust is pretty stock and I am using the airbox.

So I gave it a test run today ahead of tomorrow's rego inspection. It runs ok but not brilliantly at the moment. If I set the (brand new) petcock to "on" it runs for a little while then bogs down and stops. But if I set the fuel to "prime" it runs just fine. Last week it ran ok on "on". So I guess the vacuum hose is to blame? All the lines are clear. Any ideas? Float levels are good - I checked. I get no leaks anywhere either.

This is really starting to get to me.

[tkent02]

How much gas is in the gas tank?

What condition is the vacuum hose in?
Is it kinked?

[TheCafeKid]

How much gas is in the gas tank?

What condition is the vacuum hose in?
Is it kinked?

What he said. Depending on the model, if there's not at least a gallon to a gallon and a half in there (dunno what that is in liters ) you should put the tap on the "REServe" setting instead of ON.

[JimmyR]

Well it isn't a full tank - I'll check. And no, the vacuum line isn't kinked. I already got caught out by that one!

Thanks guys - how cool if it's just the fuel level.

[JimmyR]

I think you guys nailed it! I just didn't have enough fuel in the tank. That's a bit embarrassing! It seems to be running quite well now. Thanks. I'll just go stop wining now...

[hikermikem]

This has happened to me more than once. As TCK implied, you need more gas in the tank than you think to completely cover the petcock outlet.

The angle of the tank on the bike makes a big difference too, sometines keeping all the fuel near the back of the tank, and not over the petcock.