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FJowners.com > General Category > Yamaha FJ1100 / FJ1200 Running Problems > Fuel Starvation
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Author Topic: Fuel Starvation  (Read 386 times)
CaliFJ
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« on: October 13, 2022, 12:24:15 PM »
I’m having an issue with fuel starvation in my ‘87.  It’s a completely stock bike with that original petcock.  That vacuum electric portion is inoperative.  It’s always on per the guy who rebuilt it and stripped/sealed the inside of the tank.

The bike runs perfectly fine for the first 100 miles or so of a full tank.  Then it sputters and ultimately dies.  Once that happens, a simple shake of the bike/tank from side to side a few times will bring it back to life.

Shall I be looking at that petcock as the issue?  I’ve seen they have manual retrofit ones available.

Any direction would help.

Thanks
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Pat Conlon
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« Reply #1 on: October 13, 2022, 12:45:15 PM »
You have the classic symptoms of a pinched fuel line from incorrect routing of the line.
When cold the fuel line stays open but when heated up, the fuel line gets soft and pinches off the flow.
The 84’-87 gravity flow FJ’s are very particular about the routing of the fuel line.
See my signature line below for a link to more info.

Invest in a new 84/85 oem petcock from RPM. 2 things I like about the 84/85 petcocks are 1) no silly electric reserve function and 2) the 84/85 petcocks have a ‘prime’ (P) setting where you can turn them on manually without any vacuum signal.

Welcome to our forum

Pat
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1) Free Owners Manual download: https://tinyurl.com/fmsz7hk9
2) Don’t store your FJ with E10 fuel https://tinyurl.com/3cjrfct5
3) Replace your old stock rubber brake lines.
4) Important items for the ‘84-87 FJ’s:
Safety wire: https://tinyurl.com/99zp8ufh
Fuel line: https://tinyurl.com/bdff9bf3
FJmonkey
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bono malum superate
« Reply #2 on: October 13, 2022, 01:27:59 PM »
Welcome. My first FJ is an 86' and I had fuel issues before the cracked case issue. As Pat mentioned, the routing is very important.

I am concerned with the vacuum bypass. When your engine is off, your carb float needles/seats are the only thing preventing your tank from spilling into the crank case or the floor. Anywhere near a gas water heater or ignition source equals FIRE!

The 84/85 petcock is the way to go. Sort out this first.
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The glass is not half full, it was engineered with a 2X safety factor.

'86 Ambulance - Bent frame, cracked case, due for an overhaul
'89 Stormy Blue - Suits my Dark Side
RPM - Robert
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« Reply #3 on: October 13, 2022, 01:43:30 PM »
Flapectomy time?
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CaliFJ
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« Reply #4 on: October 13, 2022, 02:45:30 PM »
Thanks guys.  I have a call into RPM to make sure I get everything I need in one order.

I appreciate the help,

Scott
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FJmonkey
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bono malum superate
« Reply #5 on: October 13, 2022, 03:04:08 PM »
CaliFJ, are you in Kalifornia?
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The glass is not half full, it was engineered with a 2X safety factor.

'86 Ambulance - Bent frame, cracked case, due for an overhaul
'89 Stormy Blue - Suits my Dark Side
fj1289
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« Reply #6 on: October 13, 2022, 04:59:57 PM »
Pat, I’m concerned about you.  Are you feeling OK?  You didn’t mention anything about the petcock from RPM being pre-safety wired!
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FJRacer
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Pat Conlon
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« Reply #7 on: October 13, 2022, 05:23:27 PM »
Quote from: fj1289 on October 13, 2022, 04:59:57 PM
Pat, I’m concerned about you.  Are you feeling OK?  You didn’t mention anything about the petcock from RPM being pre-safety wired!

Well Crap…you’re right…
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1) Free Owners Manual download: https://tinyurl.com/fmsz7hk9
2) Don’t store your FJ with E10 fuel https://tinyurl.com/3cjrfct5
3) Replace your old stock rubber brake lines.
4) Important items for the ‘84-87 FJ’s:
Safety wire: https://tinyurl.com/99zp8ufh
Fuel line: https://tinyurl.com/bdff9bf3
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