Okay, I want to throw my petcock into a busy highway

[breckenedge]

I think I have the same problem. Just to clarify people's comments: there is no fuel filter except the one IN the petcock? There was one installed on my bike when I first bought it (20k+ mi), but I'm having similar issues after replacing it. 1979 GS750L

[jspencer241]

Just got my 550L out of the shed this morning. Rinsed and drained the tank, pulled the bowls and hosed everything down with some carb cleaner. Petcock was a little stiff but managed to get loose with some pliers. Runs great on 'prime' but will die after 5 minutes in the 'on' position. Nothing in line with my fuel or vacuum lines. I replaced the petcock last year. Thanks to this post I'll be checking the vacuum line in the morning.

[robertbarr]

wonder if I can use the following for carb syncing if I got 4

http://www.harborfreight.com/fuel-pu...ter-93547.html

It used to be common to see such an arrangement -- a bank of four of these to sync 4-carb engines. However, at $60 + shipping for 4 of them, you're really just a nudge away from the cost of a Carbtune, and you have no available means to normalize them (to make sure they all read the same, given an identical vacuum source). Maybe they're consistent, maybe they aren't. Either way, you're out $60+

I've used the gauge-type and the mercury, and the Carbtune is much easier to use than either of them. Since it's easy, it gets done a little more often, and I'd bet I get more consistent results.

... and when you're done with it, some day in the future, the Carbtune will have a decent resale value. Effectively, you're just renting it long-term.

(Now excuse me while I go collect my shill royalties from Morgan...)

[castlekin]

actually robertbarr, I was just curious if they would work only if they had them at the nearest Harbor Freight.

[castlekin]

Okay, so here is what I did, I replaced the battery. Now, everything is working just fine.

So, it looks like the battery was the issue. Conclusion, leak spark gets low compression when running. Low compression gets low vacuum. Low vacuum gets low fuel pull from the petcock.

Everything seems to be working fine now on the stand, time to take it out tomorrow for a short test ride.

Could this be the actual problem?