Running Rich???

I bought a 1981 Maxim 650 from a guy. It has 29k on it. The guy I bought it from said that the carbs were gummed up. So I bought a rebuild kit and cleaned the two jets, replaced needle and seat, and cleaned out the bowl along with the float. I put everything back together, and started it up. It runs, but at an Idle, I get white smoke thick, and when you rev the motor up, you get black smoke.



So then I replaced the plugs thinking it was bad spark and the plugs were junk. That didn’t solve my problem. I tightened the timing chain. That didn’t solve the problem. SO I pulled the diaphrams off, and check each one of the, cleaned the slides along with the needle. That didn’t solve anything.



The next thing was to pull the carbs off again, to check if the choke plunger was stuck. Pulled them all apart and cleaned the. Nothing there, SO I pulled the bowls off again to check if I was missing something. Everything checked out just fine. I reread the manual, and noticed it says not to mess with the air adjustment screw, and saw marks on that screw. SO I pulled them all out, and cleaned the needle, spring, o ring, and washer. Now I had to guess where to put them in. I started with all the way in and 2 turns back out.



That didn’t work. So I went all the way in, and tried ½ turn in increments until I got to 4 turns. I did all 4 carbs when I was doing this. That didn’t make a difference. My new plugs were black as coal. Then I ran a compression check on each cylinder. I was at about 152 on each on.



I also noticed when I had my sync tool on, I was getting gas floating on top of the mercury on all of my tubes.



I did a vacuum test on my fuel pump. That all checked out.



During all of that, I took it for a ride. It seems to pull just fine up to 9000 RPM. It does seem like it is running rather good while riding the bike, but the exhaust burns your eyes.



All in all I have had the carbs off 3 times and they all check out. I looked up the jets in it. It has 110 and 40 in it. From what I understand, that was stock.



I also made sure that the timing was correct on the bike per what the manual lays out. At this point I am out of ideas. Mostly because of the symptoms don’t make sense on what to do next. I don’t see it as a valve lash problem or a timing problem like it may have jumped a tooth on the gear.



If you have any insight, please let me know. I have about 15 hours into these carbs now. Thank you.

 

I also want to mention that I checked the fuel level in each bowl and that all checked out per the manual.

 

You might have done it already, but did you wet set the floats?

With the carbs off the bike, and perfectly level, connect a clear fuel hose to the bowl drain holes. Rig up some sort of auxiliary fuel supply. Hold the hose up to the carb body, and open the drain screw. The fuel should be level with the washer on the carb bowls, 3mm from the carb body. I have also read that you are supposed to repeat the procedure with the carbs on the bike while the bike is running... Search the forums, there are much better write-ups for this procedure...

Did you check to see that the correct jet sizes are installed?

Also, somebody is going to say it so it might as well be me... Are your valves all within spec?

Maybe a clogged air filter?

I'm by no means an expert, but it seems like the carbs are letting to much fuel in...

 

Your carbs aren't completely clean, or you have a leaky float even though the "level" has been adjusted;

and you will need to have the valves in spec to get a decent vac sync.

 

I did replace the air filter. As for when I checked the fuel level in the bowl, I hooked up clear line. I opened the drain plug and it measured about 2mm from the top of the blow on every bowl. I marked my line, and did all 4 bowls, and the level was the same. From what I have read, I see I need to re shim my valves. Would that cause so much fuel going into the motor and blacking out my plugs??

 

I had some problems getting my Seca to run well after a carb teardown and cleanout. Turned out that the air jets under the diaphragms were put back in the wrong position due to a misprint in my Haynes shop manual. Ran 'very rich' however ran pretty well. To check, the main jet that is on the center line of the carb should be a 50, and the pilot ahead of the main should be a 195.

...and yes, you will be told often that XJ's are very sensitive to carburetor and valve adjustments.