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

I use 2k epoxy for metal and plastic. Done.
But, extremely care if you spill a drop of brake fluid onto those plastics, it will crack in a 20 seconds, you will have plenty plastic to glue. This kind of plastic is disaster to save. 

We found new method how to put new diaphragms onto floaters!
Do not use any sharp tools to avoid cuts.
Just find proper strong rope with less than 1mm diameter.
Put the new diaphragm carefully onto place, adjust direction for groove, dip the rope into oil, press exactly on the edge and go all the way around  for few times. Just make sure once is done that is all the way inside (look for the membrane overall look assembly).

If someone needs more, i can send a photo how to do it exactly.

Best regards

Thanks Alan!

I never had any issue running 87, or even 85 octane in my 1200.
I rarely ever ran 91 in it. Never noticed any difference in the way it ran with regular fuel or higher octane fuel, even in the summertime.
5600-feet here in Aurora.
Compression is a bunch lower at altitude, so you can run lower octane fuels.

I always stored it with "Ethanol-Free" fuel though........Makes a difference.