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Discussion Starter · #1 ·
HELP! I don't know how to do this, but I was out for a 300 mile ride today, and just cruising home, and the bike started surging at moderate throttle. Remindend me of a carburetet motor running out of gas. What is happening??????
 

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A few possibilities but you may want to tell us more about the history of your bike.

Check the vent in your gascap. Some have been known to clog with dirt sucked up the vent tube.

Have you recently lifted the gas tank for some maintenance and perhaps pinched a fuel or vaucuum hose when you bolted the tank back down?

Maybe a throttle body synchronization would solve the problem.
 

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Hey Doc, sounds like dirt or air. Check the fuel for contamination, the air filter for excess debris. Then the lines running to the injectors. If all of the above are OK, then for me it would be time for the pro's to look at it.
Good luck.
 

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Discussion Starter · #4 ·
Thanks--
Well, it's a '05 with 10,000 miles, a PCIII with the zero map, Two Brothers mufflers. I synched the throttle bodies at about 4000 miles, and it's run perfectly since day one. No engine codes coming up on the LCD display, ever. Havent been working on it or raising the tank lately, the problem came on all of a sudden. Will idle fine and runs smooth when hard on the throttle. Been riding it every 1 to 2 weeks, and on a Battery Tender the rest of the time, sits out in the cold, but under a carport and bike cover. I run Chevron Premium exclusively, almost always from the same station. Feels almost like it's running on 2 or 3 cylinders when it happens on the highway. The throttle bodies can't go out of synch all of a sudden, can they? Is there a fuel filter I can replace easily? Dang....
 

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Vetman, two Aussies have had trouble with irregular running. I am not sure if they inculded surging.

Atlas, registered here (last posted under Aussie ride outs, I think) traced his to leaking vacuum hoses under the tank - PM him to get details.

Fastdevil, AKA Butts (you'll also find posts from him in the Aussie section) also had trouble recently with irregular running that was very hard to diagnose. Trace him and PM him, maybe he also has some tips.
 

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Friend of mine has a PC unit. I have a PC unit. His went south, sounds similar to what you are saying.

Take your PC unit out of the circuits. See what happens.

vetman said:
Thanks--
Well, it's a '05 with 10,000 miles, a PCIII with the zero map, Two Brothers mufflers. I synched the throttle bodies at about 4000 miles, and it's run perfectly since day one. No engine codes coming up on the LCD display, ever. Havent been working on it or raising the tank lately, the problem came on all of a sudden. Will idle fine and runs smooth when hard on the throttle. Been riding it every 1 to 2 weeks, and on a Battery Tender the rest of the time, sits out in the cold, but under a carport and bike cover. I run Chevron Premium exclusively, almost always from the same station. Feels almost like it's running on 2 or 3 cylinders when it happens on the highway. The throttle bodies can't go out of synch all of a sudden, can they? Is there a fuel filter I can replace easily? Dang....
 

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Just noticed you also said you use premium. DON"T! No need. I used to use premium in all my vehicles. Finally read enough articles to convince me not to. One of the final ones mentioned a fellow running premium and getting dirty looking pipes, weird running and such, switched to regular, and the bike cleaned up it's action.

FJR runs just great on regular and PC unit. In my last note I said my friend's PC unit went south, they replaced it under warranty fortuneately.

vetman said:
Thanks--
Well, it's a '05 with 10,000 miles, a PCIII with the zero map, Two Brothers mufflers. I synched the throttle bodies at about 4000 miles, and it's run perfectly since day one. No engine codes coming up on the LCD display, ever. Havent been working on it or raising the tank lately, the problem came on all of a sudden. Will idle fine and runs smooth when hard on the throttle. Been riding it every 1 to 2 weeks, and on a Battery Tender the rest of the time, sits out in the cold, but under a carport and bike cover. I run Chevron Premium exclusively, almost always from the same station. Feels almost like it's running on 2 or 3 cylinders when it happens on the highway. The throttle bodies can't go out of synch all of a sudden, can they? Is there a fuel filter I can replace easily? Dang....
 

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I'll revise my list to:

Disconnect your PCIII. (Always suspect.)

Blow out the vent tube from the gas fill to where it dangles under the bike. (Easy to do with an air hose or canned air.)

Fill up with 87 octane fuel. I was going to say to replace the fuel filter but I couldn't find one on the parts fiche. May be part of the fuel pump (in the tank) or pressure regulator. (Eliminate the possibility of contaminated or incorrect fuel.)

Check your vacuum hoses for leaks, cracks, or loose connections. (Vacuum hoses suck, no, really. When you take your car in for diagnosis, the mechanic usually starts playing with the vacuum hoses.)

Check your throttle position sensor. These are one of just a few weak links on the FJR and a search on the old board will give you enough info to tell if yours is bad. (Many FJRs have suffered this malady and your symptoms warrant a TPS examination.)

Replace your sparkplugs. If they were replaced at 8000 miles (doubt it since you said you had not lifted the tank) do it again. Sparkplugs are more fragile than you think and an invisible hairline crack in one can cause enough problems to make you want to sell your bike. (This is the first on the list that isn't free, but a look at the plugs will show if just one or all of your cylinders are affected too.)

And no, your throttle bodies will not go out of sync all of a sudden unless a screw falls out. This is unlikely, but not impossible if you had to back one of the screws out quite a ways in order to sync a cylinder. I had a screw that was very loose when I finished, so I developed the Unauthorized TBS and it solved that. You can find info on that with a search on the old board.

If the bike is not fixed at this point, put down your tools and step away from the bike. It is time to take it to a professional. With all the money you are throwing away on premium gas, the money spent for a real mechanic shouldn't be a big deal. :)
 

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Discussion Starter · #9 ·
Well, I went out for a couple hundred miles in our beautiful sunny Arizona weather the other day, and guess what? The bike seemed to run fine again! Maybe just my imagination now, but only a VERY slight roughness at idle. Went to iridium plugs at about 4000 miles, so maybe I'll switch them out and check all the wires and hoses and synch the thing again. Maybe just some bad gas, or temporarily plugged hose?? Ya got me.....
 

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I run a Iridium plugs. They are supposed to last a long time. Someone once posted that he checked his at something like 20k miles. Were still looking good. Replaced them cause he already had a set ready to go. Said next time he's going to wait about 30k miles. I understand in cars they can do somthing like 100k miles. :lol:

vetman said:
Well, I went out for a couple hundred miles in our beautiful sunny Arizona weather the other day, and guess what? The bike seemed to run fine again! Maybe just my imagination now, but only a VERY slight roughness at idle. Went to iridium plugs at about 4000 miles, so maybe I'll switch them out and check all the wires and hoses and synch the thing again. Maybe just some bad gas, or temporarily plugged hose?? Ya got me.....
 

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Discussion Starter · #11 ·
So out I go yesterday for a couple hundred miles, was re-fueling at a location about 2000 feet lower in elevation, noticed a WHOOSH noise as I opened the gas cap, don't remember hearing that before. Is that abnormal? Clogged vent? Which one, if any?
 

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@vetman

You don't say your location/what current ambient temperature is...

Very hot weather/very hot bike obviously expands the remaining air in the tank, this can cause your problem.

But, a big BUT, it can also be a clogged gas tank vent, which will create a vacuum as the fuel level goes down, which gets worse the more the fuel level drops, which will then implode your tank. This has happened to someone very recently on this site.
 

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Based on your discription, I'd bet money on the TPS (throttle position sensor). They tend to be very intermittant when they start to go bad. Sometimes going weeks between incidences. When they exihibit the problem it is generally just when slightly applying some throttle. Idle no problem, decel no problem, significant acceleration no problem, very light acceleration such as when maintaining a certain speed, significant stumble or surge. How do I know? I dealt with the problem for about 9 months before it got bad enough that the dealer was able to diagnose it and replace the TPS. Haven't had a stumble sinse.
 
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