When I first rebuilt my GS500 carbs to go on my GS450, I set the float height according to the service manual (14.6mm +/- 1mm) with the normal routine: carbs not mounted to the bike / tilted at an angle / touching the float needle but not "pushing" it, etc. Everything seemed to be running well although I knew I was on the rich side with my jetting from the start (GS500 jetting on a 450cc motor.....). Recently I swapped my stock 2-2 exhaust with a 2-1 exhaust w/ a Supertrapp muffler and that's when I started having real problems. Seemed like no matter what I did with the jets I had the same rich stumble between 4 & 5k rpm. I double checked the float height using the tube method and my left carb's fuel level was above the gasket surface.......
Basically, I've been in and out of the carb multiple times now bending the tab that the float needle rests on and it seems to make little difference with the actual float height. Anything I could be missing? Anybody have a sinking float, or a float needle that "drifts" on that tab?
89-00 floats drift, but not in the time span you are talking about. You may have a bad O ring in the spigot, or the float retaining O ring is bad.
Cool.
Buddha.
Thanks Buddha. I should have said: every bit of rubber inside the carbs was bought new about a year and a half ago. Maybe this week I'll swap the floats and needles between the left and right carbs......and if it rains like they are calling for I'll pull the rack and try and set them to spec again.
First thing, did you use OEM needle valve sets? I had bad luck with K&L.
Second, you could check for a sunk float. Is there any fuel inside one of the plastic floats. One good way to test is to submerse them in water and look for bubbles that indicate water entering the float.
Oops.... I forgot to update this.
It was a simple case of: messing with the carbs, and the carbs mess with you. Somehow in my foolishness I bent a slight "U" shape in the tab that the float needle rests on. Once I pulled both float assemblies out at the same time, I noticed the difference between each side.
But thanks gentleman! Always good to have a place to bounce ideas and troubleshoot.