air/fuel mixture??

Hey guys, i found this site recently and it looks awesome. I have a 1981 XJ650 that i recently cleaned the carbs on. I installed new needles and needle seats. The floats looked fine and i have no gas leaks. I think the problem now is it's running rich. A fair amount of black smoke and the plugs are black. It also seems a little sluggish and starts to open up at about 3500RPM. i also seem to be using too much gas. Does anyone know where the air/fuel mixture screws are on the carbs and what the factory settings might be? Thanks !!!! Eddie

 

I could be a result of many different things:

-your air filter is dirty

-your fuel levels in carb bowls are too high, you should adjust your floats to specs

-your choke cable doesn't return all the way back so your choke is always on

-you run the wrong type of spark plugs (too cold)

-your mixture screws are too far out, 2 1/2 turns out is a good start, they are located here:



They might be hidden under brass caps, though, then carefully drill these caps and remove them with an extractor.



Don't forget to run a big fan in front of your engine while adjusting your mixture, these airheads can get too hot.

 

. . . and "step #1" is always "get valves in spec" if you haven't done this already.

Welcome !!

Safety warnings \/

 

Québécois that rack should be the poster child for The Church of Clean.
Nice! 8)

 

I can't take any credit for that, I got it on ebay as is!

I will probably sell it though, because I don't own my MAxim 750 anymore...

 

Good advice here. I would add that you should get a colortune plug to help set the pilot screws. I realize that 2 1/2 is the standard starting point but for me that resulted in a rich conditions and sooty plugs. I used the colortune plug to first set the pilots to a lean position and then open enough to get a good blue color and smooth idle. Then I put in new plugs and tweaked the pilot screws to get the right color on the plugs. My pilot screws are all less than 2 turns out, and probably closer to 1 1/2. By adjusting from a lean setting I was able to easily see the change of color on the plugs. That said, this isn't going to work until you get the valves set, the carbs adjusted as above and synced.

 

Perform a: "Clunk Test"

Refurbish and Polish the Diaphragm Piston Bores.

"Scrub" with ScotchBrite Pad (Gray)

Polish Bores with Dremel Tool using Jewelers Rouge's #5 & #6.

 

Thanks alot guys.... Will do.. Eddie

 

This might help: http://www.xj4ever.com/setting%20fuel%20levels.pdf

Plus: http://xjbikes.com/Forums/viewtopic/t=14827.html

And: http://xjbikes.com/Forums/viewtopic/t=29209.html

 

old thread reply.
I just received colortune.
Carbs were tore down 3 times and cleaned. Except the fuel/air screw was never removed.
I have bench synced them and set float heights to spec
Once back on bike, I synced carbs with a set of guages
Colortune resulted in all carbs to be approx 2 1/2 tuens out, except #1.
The only setting to get the blue was with the fuel/air screw turned all the way in. Anything other than that went to an orange color

My question is, can this be run for awhile until parts get here?

 

Please don't do this. There is no need. Clean is fine.