I found the problem with the Petcock on my 89. The PO must have been in there at some point as the spring was missing behind the diaphram. No wonder it didn't work on run.
So looks like I need to replace it. Anyone have any experiences good or bad with the K & L unit?
Been there with my '90, not sure what was exaclty the issue, but my petcock was causing an impropper fuel level in my carbs.
Probably due to K&L replacement needle that I replaced, that has a stronger spring compared to OEM needle. But I took care to propperly set the float tab to allow for propper level.
Probably too, because my engine is around 100.000Miles and valve wear does not cause a propper suction to propperly open the petcock.
Probably too, because I replaced the tank-petcock-carbs rubber tubes with vinyl ones, that use to reduce diameter after some time in contact with fuel.
I could see that newer GS use a different petcock, with larger diameters. I purchased a used petcock and it solved my problems. But that newer petcock will not bolt right in the older model room. Some modification is required.
My advice: Mess with a single thing a time. Now I'm mad because I don't know if the K&L needles are OK, float level is OK, valves are ok?..