GS550 Wont Rev Past 6000-7000rpm Under load

[octusis]

Bike seems to rev fine in neutral, 9k-10k rpm, as soon as you put it in gear and ride it around it doesnt like to go anywhere above 7k, it also seems to make some noise when its under load aswell, but only when it hits 6-7k, any help very appreciated!

[jaffa90]

Needs more fuel under load so does it have a vacuum operated fuel tap or a PRI position?
Has anybody tampered with the carbs?

[temeluchus]

Simple things first, drain the float bowls as if you have water i there it can cause this. Then the fuel tap and its operation.
____________________
Some shite cruiser. Now with guns and FREEDOM!

[octusis]

[octusis]

[temeluchus]

open the fuel cap and see if it runs properly. Could be a blocked breather.
____________________
Some shite cruiser. Now with guns and FREEDOM!

[octusis]

[jaffa90]

Has it got a good fuel flow to the carbs?
I`m assuming the fuel level in the carbs are correct when the float needles shut the fuel supply off!

[Robby]

It's only struggling under load because the problem is related to getting enough fuel, rather than related to revs. It takes very little power to get an engine to 9000rpm with no load. It takes ten times as much (rough figure, don't go autistic) to get there with a load on the engine.

It could also be electrical, but let's look at fuel first.

At medium to high engine loads the fuel is flowing through the main jet, up the emulsion tube, and around the side of the needle. If any of these parts are blocked, broken, worn, the wrong size or the wrong setting (for needle height), it won't make power.

In addition, if the fuel height is wrong in the float bowls you'll get problems, or if you have an air leak due to a poorly fitted or cracked inlet rubber, or a missing cap on one or more balancing ports (where you fit the carb balancers).

So, job number one, make sure the carbs are set up according to the factory settings and clean. Bits to check are:
1. Mixture screw position - not a problem in this case, but good to check while you're down there. Factory setting is normally around 2 turns out.
2. Needle height.
3. Jet sizes and condition.
4. Float height.
5. On CV carbs, is the diaphragm in good condition.

You could also have an upstream fuel supply problem - fuel filter or tap clogged. In that case it would probably start and have power for a few minutes, then lose power as the float bowls empty and aren't refilled quickly enough.

Finally, for added fun, I know the GS650 can be an utter bastard to make it behave when you fit a fuel filter. So if you recently fitted a fuel filter and it started misbehaving, try without it.

[octusis]

[octusis]

[jaffa90]

[octusis]

[jaffa90]

If you are happy with the fuel supply how about the spark advance and retard mechanism working ok?

[octusis]

[octusis]

Update: I'm pretty sure I've got the bike running better, I lowered the float level to make it more lean, it must've been dumping raw gas through the jet (i'm guessing) I appreciate all the help and if this helps anyone else going through the same issue then great

[Robby]

Did you guess the float height, or set it according to the workshop manual?

Good that its running better, but you should set up carbs properly. The settings will be in the Haynes/Clymer/Manufacturer workshop manual. If you can't find a digital copy from googling, it should be less than £20 on ebay.

[octusis]

[jaffa90]

Have you any SIDE pics of the floats hanging down and again with the carbs upside down with the floats in the shut off position?

Also are the float valves sprung loaded?

[Robby]

That sounds like the floats are in upside down.

Usually the bottom of the float is flat, and the top is profiled to sit into the carb body around all of its curves and protrusions.