Topic: Bike runs rich no matter what

[schwabbyboy]

I've had this bike about 4 months now and I am having some issues with it. A lot of the work I have done so far has been guided by forums, mainly this one, so I'm hoping you guys can help me out.

The bike is a 1972 CB750 K2 with 43,000 miles on it. My main issue is that no matter what I seem to do the bike runs rich, especially at idle. Any time I'm stopped at a light I end up with a gassy cloud around me. It's not pouring out smoke, but it's enough to have me concerned.

The bike ran after I cleaned the carbs the day I got it. Started up first kick, and I've put almost 3,000 miles on since. It runs, which I suppose is good, just not well. Today I changed the spark plugs, which were clearly carbon fouled. They looked like they hadn't been changed in quite a while though. I put 4 brand new NGK plugs in it. I know replacing the plugs is one of the first things I should've done ( still learning) but even after replacing all 4 plugs plugs there seems to be no change. I've also meticulously disassembled and cleaned the carbs many times, including bench syncing and setting the floats to the correct stock levels. I have (to the best of my ability) tried to tune the carbs via the air/fuel screws, and no matter what the bike runs rich. The bike came with pods on it, and a Polaris Pure quad exhaust that the PO welded on.

Please let me know if I'm doing something wrong or what I can do to correctly tune this bike.

[754]

Check to see if they drilled out the pilot jets.

[Don R]

 Most guys here will tell you to return it to a stock air filter and factory jets.  That's just because it is the best baseline to work from. I have no idea what the exhaust is but unless it's very restrictive is should be ok.
 I've seen bikes with drilled jets and plugged exhaust, bent float pivots, wet gas, junk in the gas making the float valves leak, Worn float valves and floats with wear points where the float rubs on the valve, floats upside down and slides in backwards.
 Just a few ideas.

[calj737]

I would determine what jets are in the bike and not presume they were drilled. If the bike had pods, someone certainly may have changed to much larger pilot jets to accommodate the lean condition of the carbs.

Once you sort out the jets, if the condition persists, a Clear Tube test of the fuel level actually occurring is needed. Resolve that so the fuel is 3-4mm below the bowl seam, and then see if the problem persists.

Lastly on your carbs, verify the choke flap is correctly set too and removed (set to full open) once the bike is warmed up.

If you still have issues, then you need to carefully inspect the ignition for weak spark.

But your problem is likely within this regimen.

[PeWe]

I have had similar problems 
1.) Sounds as flooding floats
2.) Ignition might have an influencce too. If the springs are too sloppy, full advance will happen way too early.
     Possible to fix by cut them.
http://forums.sohc4.net/index.php/topic,131339.msg1464986.html#msg1464986

[754]

Doesn't much matter what the jet size says, once they are drilled.
 Like the set on here the other day  double the size, which equals 4 TIMES the VOLUME..
Pretty hard to expect it to work..