Help with carb settings on Xt 600 43F

[Pawlie]

Hi Folks,

Looking for a bit of carb help. I searched and searched other posts but couldn`t get to the bottom of my carb setup issues. My carb is the old style with the piston type secondary.

I have never messed with the carb settings as the bike has run well but has always suffered from the dreaded hiccup when the secondary kicks in. I have always just worked around this as backing off the throttle a bit from wide open typically allows the bike to rev out as it should.

My problem is the bike seems to gradually run richer over time. Typical fuel consumption was 60mpg now it`s proabably 50-55mpg. Also cold starting is suffering. The bike has always started 2nd kick when cold 1st when hot. Now it takes 5-6 kicks when cold. Hot remains at 1 kick.

I have recently completed a full teardown for new rebore,piston,rings. I am paranoid that the rich condition is going to wash the oil off the cyl. walls and result in a premature rebore the next time. That`s my motivation for getting the jetting right.

I am trying to baseline the carb settings to recommendations in the manual and Aukeboss who often seems to chime in on carb questions.

The Clymer manual talks about a Carburetor full open adjustment. Basically, setting the throttle valve(primary) to stop once the throat of the carb is fully exposed. Problem is my bike doesn`t seem to have the necessary adjusters as depicted in the manual.......and it does not stop where the manual suggests it should.......what to do.

Aukeboss has recommended to set the secondary to open at 7mm vs. 5mm as suggested in the manual. Is this correct for the old style carb. The manual also recommends to do this adjustment with the throttle cables attached. Is this necessary.

The manual says to leave the pilot air screw alone. Aukeboss recommends adjusting it. Currently it is 4 turns out from fully in. The bike is rich, should I be turning it in or out to lean.

The mains are both 130 and very likely stock, is this ok.
Aukeboss suggests needle in the 4th position. Seeing as my bike is kinda rich, would it be wise to drop the needles 1 position.

Is there some way to test that the secondary (vaccum operated) throttle valve is actually opening as it should. Does the throttle valve piston ever wear out. When operating it by hand it is nice and smooth.

The viton tip on my float valve is showing its age but......canèt get a replacement. Is this a problem.

Sorry for the lengthy discussion but I have zero carb tuning experience. Kedo says they are working on a rebuild kit for the 43F carb but not available at this time. Some of the stock Yamaha rebuild parts are becoming discontinued for this carb......getting a little worried.

Has anyone else suffered this gradual richening condition over time. What was the solution.

Sorry about the lack of proper question marks, my computer does ééééé when I hit the question icon for some reason. Wierd

Many thanks for your time and assistance,

Pawlie