I'm stuck at 4500 rpms

[thatdood]

Most of the time I've owned my GS, it's been sitting in my living room waiting to be let loose. So I still don't really know The Goose yet.

Last night, I learned some more.

I finally got it outside, started, and running after some minor charging issues (that good ol' regulator).

Now, there's something else.

I was finding that my bike wouldn't rev too much higher than 4500rpms. Late last year, I had the carbs rebuilt by a local shop (never doing that again) and they told me they were having trouble with a lining in the fuel rail collapsing and restricting fuel flow to the outer two carbs, 1 & 4. (Did they tell me the truth?) But eventually they said they figured it out, I paid them a small fortune, and went on my merry way.

So last night I start it up, and she seemed to be idleing (did I spell that right) pretty well. I could even rev her up to 8 or 9 grand in the yard. But when I took her out and tried to get on the throttle a little, she would get to about 4500, and that was it. She didn't rev higher, and there was no power after that. She didn't cut off, and that was good. But ultimately, I could do any more than 45 or 50 mph, even in 5th gear.

Is this a fuel thing? Is she too rich? Is there not enough fuel flow from the carbs (bowl, jets, needle valves, etch.)? Has anyone even heard of this weirdo problem?

All in all, it was nice not having it just sitting in the living room.

Thanks everybody,

thatdood

[Dave8338]

Most of the time I've owned my GS, it's been sitting in my living room waiting to be let loose. So I still don't really know The Goose yet.

Last night, I learned some more.

I finally got it outside, started, and running after some minor charging issues (that good ol' regulator).

Now, there's something else.

I was finding that my bike wouldn't rev too much higher than 4500rpms. Late last year, I had the carbs rebuilt by a local shop (never doing that again) and they told me they were having trouble with a lining in the fuel rail collapsing and restricting fuel flow to the outer two carbs, 1 & 4. (Did they tell me the truth?) But eventually they said they figured it out, I paid them a small fortune, and went on my merry way.

So last night I start it up, and she seemed to be idleing (did I spell that right) pretty well. I could even rev her up to 8 or 9 grand in the yard. But when I took her out and tried to get on the throttle a little, she would get to about 4500, and that was it. She didn't rev higher, and there was no power after that. She didn't cut off, and that was good. But ultimately, I could do any more than 45 or 50 mph, even in 5th gear.

Is this a fuel thing? Is she too rich? Is there not enough fuel flow from the carbs (bowl, jets, needle valves, etch.)? Has anyone even heard of this weirdo problem?

All in all, it was nice not having it just sitting in the living room.

Thanks everybody,

thatdood

The part about the lining in the fuel rail has me confused. Not sure what they are talking about. The fuel rail on these bikes are integrated into the carb bodies proper and are connected by inline tubes with orings or rubber coated tubes with the orings built in, it depends on year and model, on the #1 and #4 carb bodies. The #2 and #3 are connected in the same fashion only instead of connector being a straight inline unit, it is a tee. This is the primary fuel feed for all the carbs. You are having fuel problems alright, but by what you explained, it sounds like you are running short on fuel in the midrange. This can be caused by several factors.
1) Petcock issues...have you checked to see that the fuel screen inside the tank is clean? Do you have an additional inline filter on it?
2) The petcock itself...check to see that your petcock is flowing free in the run/on position if it is a non vacuume actuated unit or in the prime position if it is a vacuume opperated type.
3) Air leaks...Start with the air box itself. Is the seal intact around the cover, stock filter (lightly oiled) greased at its' mounting point with the airbox, all connection points along the airbox side of the carbs and also on the intake side at the carbs and at the head. (some use orings between the intake boots "8-valve round cam covers" the 16 valve square cam covers do not.
4) Float level is another source of fuel restriction. If you didn't set it, you don't know where it's at.
5) Jet needle height, when all other areas are ruled out and you're still having issues, this would be the next thing to check.

Give it a try in the order listed and hold off on the jet needle option, if you're still running the stock air box.

Let us know what you find.

[Otto]

Just a thought, could it be the ignition advancer there is stuck?

[nabrams]

Before you start tearing things apart (which you will almost certainly need to do), do some more testing:

1. Check that 1 & 4 spark plugs are firing, both at low and high RPM (visual verification - if you don't know what I mean, do a search on how to verify spark). 1 & 4 are connected to the same coil - the coil may be just fine at low RPM and fail at higher RPM (see Wikipedia explanation for degrading coil performance at higher firing rate). With no load the bike will easily rev high on two cylinders, but bog under load.
2. Run the bike at its max RPM (now 4500) for a few minutes and hit the kill switch and coast to a stop. Check the plugs. Are 1&4 black? - If yes, then they're not firing or the mixture is way too rich. Compare plugs 1&4 to 2&3.
If 1&4 plugs are white, then either too little fuel or too much air is present. Air leaks are VERY common on these old bikes - see the TONS of posts on this issue.

Once you've done these tests and read othere posts, you'll know where to start.