1980 XS850 Midnight Special Carb Issue

[knightops]

Hello Gentlemen,

I seem to be having some problems on my restoration with the carburetor. I am using a colortune and can't get the bike to run at all on Zero Choke. All cylinders fire at half choke but number 1 stops firing at full choke. At half choke, number 2 and number 3 fire with a blue flame. Moving the pilot jet does absolutely nothing to change the color. Full in or full out has zero effect. My spark plugs are covered in black soot with obviously suggests a highly rich fuel mixture.

I am by no means a carb expert but the only thing I can think is that possibly the floats are too high making the fuel so rich that the pilot jet has no effect. This would also account for the choke levels and the way it is running. Full choke, so rich that number 1 doesn't even fire (is this possible?) and number 2 and 3 are yellow. Half choke, everything fires at a blue flame except for 1 that fires with a yellow. Zero choke, everything dies. Although it would make sense that number 1 would continue firing.

I am hoping that you guys can help me out, I may be way off. I followed the book precisely with a caliper when adjusting the floats, but I am certainly not beyond screwing it up. Thank you gentlemen.

[motoman]

One question is, did you replace the float needles in all the carbs? Correct float adjustment won't keep the levels equal if one or more of the viton needles isn't seating properly. Other than that, more specific info needed on what exactly was done with carbs.

[jetmechmarty]

It sounds like maybe all four of the pilot jets are plugged. It only idles when you draw fuel through the choke tubes. That's what I think from the information given.

[knightops]

Thank you

Thank you both for your replies.

Motoman- The float needle valves were replaced with those that came in the rebuild kit. All gaskets and needles/jet were replaces with new ones.

Jetmechmarty- I certainly see what you are saying. I do have a question though, why would it rev higher/run better at half choke if it is starved even more for fuel at that point?

I've got the carbs off and the float levels look good. I used the clear tube out of the drain hole method. Any other ideas? I will be taking a close look at the pilot jets.

[knightops]

Update

I just got done with looking at the carbs further and all the jets look really nice. Nothing in them what so ever. I did have another question though. If the floats are set too high, how much lower would make a noticeable difference? 2mm lower? 3 perhaps? Thanks again.

[jetmechmarty]

Jetmechmarty- I certainly see what you are saying. I do have a question though, why would it rev higher/run better at half choke if it is starved even more for fuel at that point?

I said that because the choke is a circuit independent of the pilot.