Hard Starting 1980 GS550E

[elkapower]

Well being new to the board, where do I start.
After rebuilding the carbs, the ones with the plug on top hiding the air fuel mixture screws that get frozen in, all parts are new and rebuilt. Have dialed the bike in with an IV gas bottle, put the tank on, won't start.

So, rebuild the petcock valve, nothing insanely wrong, just a small bleeder hole plugged, it's together, still won't start.
Full choke on, nothing; choke off, nothing.
Engine turns over, sometimes after choking it, waiting 2 -3 hours, she might catch and fire, but most often, won't stay running. javascript:emoticon(':dunno:')
It has to be the valve, haven't balanced the carbs since I can't get it to stay running. Is there an aftermarket petcock solution to this piece of s*#t.
Help, want to ride this girl.
Thanks for any suggestions, heard of many others having this problem, never a salient solution that I haven't already tried.

[scratch]

Welcome,

Most common prob has been pinching the fuel or vacuum lines when putting the gastank back on. Try opening the gascap, too.

[elkapower]

A pinched tube would be so sweet, but not that simple I fear, have been thru the easy stuff, and the carbs have been off multiple times, such a pain. Has anyone had experience with a pingel shutoff as a cure?

[scratch]

Have dialed the bike in with an IV gas bottle, put the tank on, won't start.

So, rebuild the petcock valve, nothing insanely wrong, just a small bleeder hole plugged, it's together, still won't start.

It has to be the valve,

Thanks for any suggestions, heard of many others having this problem, never a salient solution that I haven't already tried.

I think you've already answered your own question, but did you check fuel flow to the float bowls? In the On position? In Prime? In Off or Reserve?

[JamesG]

Clarify:
The bike ran fine with a pony fuel tank?

The bike won't run *at all* with the bike's gas tank installed? Not even for a little while after putting it on?

[Blueknyt]

yeah, was gonna say even with tank /vavle messed up, should still fireup with whats left in bowls from IV tank