'86 1200 stalled on the freeway

[Tarkus]

Greetings,
Yesterday coming home after a ~300 mile ride, doing 75 in a carpool lane suddenly experience a loss of power. Carefully started changing lanes and while doing so the symptom keeps getting worse, bike starts sputtering and in the first lane stalls as I pull the clutch and roll to the shoulder. Cranked it several times with no luck, sounds like there is no fuel, however the tank is 3/4 full. While on the phone trying to summon help, tried one more time and the bike starts. I immediately jump on it and thanks to FJ's powerful engine reach freeway speed in couple of seconds  .
   About 3 miles away from home I get the same problem, wait for 5 minutes the bike still won't start. Out of ideas I pull the choke out and the bike starts as if nothing happened. Rode the bike back home with the choke pulled.
  Any ideas?

I have a new OEM petcock, that I had installed 2 days prior.

[racerrad8]

Gas cap vent.

You need to do the infamous "flapectomy".

Randy - RPM

[Tarkus]

Scared to ask, but what is "flapectomy" and how does one perform it.
I am very new to FJ, only about 2 months.

By the way, thanks for the quick shipment of the petcock Randy.

[big r]

It is in the files section. You need to dismantle the cap and remove the orange rubber pieces to prevent a vacuum from happening. Works wonders and dont ask how I know

[racerrad8]

I have the file attached from the old Yahoo files.

I only remove the two screws for the lock assy and the one screw on the plate retainer.

I do not remove the detent screw, spring & ball. (something will get lost...)

I also remove the complete plastic piece with the orange discs and discard it.

They can be re-installed incorrectly and cause the same problem as the flappers...right monkey...?

Randy - RPM

[giantkiller]

Sounds like the famous flapectomy alright. But If after you perform the flapectomy. You have the same problem again. Ask yourself if you have a fuel filter on your 86. And if you do...remove It...

[racerrad8]

Also, make sure the fuel line is routed correctly. It is counter intuitive, but it is supposed to run under the Y.

Randy

[Tarkus]

So I scrounged the forum on more info on the "flapectomy" and if I understand correctly it prevents the possible vacuum in the tank.
But if that's the case shouldn't opening the gas cap immediately alleviate the problem (which is the first thing I did)?
I have also noticed that when I have little below 1/4 tank left the bike won't start until I fill it. It almost seems like I need the "full" pressure of the full tank to get the gas through the plumbing. Could there be a blockage somewhere? I checked all the lines, nothing is pinched and the routing is correct (no fuel filter either).

[Pat Conlon]

Ok, so....Gas cap venting, nope. Fuel line routing, nope, Petcock internal malfunction, nope, new petcock.

Check your vacuum line to the petcock. Make sure the hose is in good condition (no cracks, no kinks) and that it's long enough. I say 'long enough' because after trimming the cracked ends of my oem hose for 20 years, I ended up with a hose that was ~3/4" too short. The line fit fine (I thought) only to partially seperate off the petcock during a long ride.

My symptoms were exactly the same as yours. I thought it was the gas cap too, only to rule that out when opening the cap made no difference. I was able to identify the vacuum signal problem on my '84 when I put my petcock into the (P) prime mode and I was able to continue the ride. Unfortunately this is something you can not do on your 86/87 petcocks.

Also make sure both sides of the vacuum line is clamped.

If the vacuum line is good, the only other thing I can think of is that something is happening on the electric petcock. Like this : http://www.fjowners.com/index.php?topic=17122.0



Please report back. Hope this helps.  Pat

[FJmonkey]

They can be re-installed incorrectly and cause the same problem as the flappers...right monkey...?

Yes, this part is worthless without the silicone flappers so just toss it out. Upside down it will seal the cap and prevent venting. My other problem on my '86 was solved after doing the Suck test. The petcock was not holding vacuum and was also not allowing proper fuel flow. The lower the fuel level the worse it was.

[Tarkus]

Thank you all for your help.
Since the petcock is new I doubt that's the problem.

I will check the vacuum line end-to-end.
Could it be something with the carbs, like a punctured diaphragm (I had that problem on my tankless water heater  ) ?