Is it starving all the time or only when hot? If when hot only have you done the flappectomy?

Quote from: red on March 24, 2026, 12:55:49 AMMarioR,
Mouth suction on the vacuum line should be enough to make the petcock flow. Block the vacuum line, holding the vacuum, and the petcock should continue to flow. Otherwise, the diaphragm (or the vacuum line) is leaking. Releasing the vacuum should stop the flow of fuel.
Personally, I would replace a malfunctioning petcock, rather than repairing it. It has done enough years for you already. A new run of vacuum line to the new petcock would not hurt, either.
YMMV.

Will play with it today and if no good result, as Pat said, will order new manual petcock 84/85.

Thanks

Quote from: T Legg on March 23, 2026, 11:24:35 PMIt could be that your fuel line isnt routed correctly and is getting pinched off.

Fuel line is new and direct to Flat carbs, Mikuni's 38 so no pinch line.

thanx pat. I recently got a KTM 390 adventure plus my fjr 1300. it's getting difficult to ride all three of them and I hate a bike just sitting. needs to go to a good home

It used to be called a flapperectomy if i remember. Anyway scroll through this link > https://www.fj1200.info/carbtuning.htm and you'll find out about the thing. HTH.

The fuel filler door on the fuel tank makes a wheezing sound after I shut off my 86 FJ1200? If I open the door the sound stops but when I close the door the tank starts to wheeze again. It will make the noise for a few seconds then stop and restart again, Freaky huh? Any ideas?
Clogged vent perhaps? If so, where is the vent and how should I clean it? Is it a pressurized tank?

MarioR,
Mouth suction on the vacuum line should be enough to make the petcock flow. Block the vacuum line, holding the vacuum, and the petcock should continue to flow. Otherwise, the diaphragm (or the vacuum line) is leaking. Releasing the vacuum should stop the flow of fuel.
Personally, I would replace a malfunctioning petcock, rather than repairing it. It has done enough years for you already. A new run of vacuum line to the new petcock would not hurt, either.
YMMV.

Quote from: T Legg on March 23, 2026, 11:24:35 PMIt could be that your fuel line isnt routed correctly and is getting pinched off.

I agree with Travis...pinched fuel line would be my first choice.
It happens often,  that's why I have it in my signature line.

If it's not the fuel line, then it's that wonky electric reserve 86/87 petcock.
 I would throw it away and put in a new oem 84/85 petcock from RPM. It's plug and play.

It could be that your fuel line isnt routed correctly and is getting pinched off.

Quote from: RPM - Robert on February 24, 2026, 10:35:03 AMCorrect on the 86/87 model it should not flow any fuel until vacuum is applied. If it is flowing fuel the petcock is bad.

The 84-85 has a prime function which will flow fuel when the selector switch is in the prime position but in the on position it should not flow fuel until vacuum is applied.

So looks like I still have some issues with gas supply.
Petcock does not leak so I assume membrane is still good/or not??? However, starving for fuel - means issue with vacuum??? Vacuum hose looks good so solenoid doesn't work???

Thanks

Thanks