Topic: CB 750 carb help?

[slowjo]

I just recently cleaned the carbs on my 1971 CB 750 K2 and it is now running rich. While it sat over winter one of the carbs overflowed so I thought it was a good time to tear into them before riding season. So I purchased Hondamans book and cleaned everything I could. I opened up the emulsifier tubes. The jets are 40 and 120. The needle clip is in the stock position. The only other changes I did since last year is add one of Hondamans transistorised ignitions. Even if I run it without a airfilter it still blows black smoke out the pipes. I'm running the stock air box with a Mac 4 into one. Does anyone have any suggestions on what I should do next?

[hijynx]

I ran into the same thing last week. I checked my float heights - they were too "low" as in the fuel level was too high. also after also reading hondaman's book. on page IV-12 right below where he talks about drilling the emulsifiers he talks about how intake leaks can make the mixture rich instead of lean as conventional wisdom would dictate. I tightened the bejeesus out of the air boot clamps. between those 2 things that seems to have cured my rich running condition.

[Groover]

If adjusting the float level and tightening the clamps fails to do the trick I would inspect the jet needle for wear. Even a little apparent wear is enough to upset the mixture and make the bike run rich. Replace bothe the jet needle and the needle jet with genuine Honda parts. Hope this helps.

[slowjo]

Everything is tight. I checked for leaks and did not find any. If I run it without a airfilter and choke on it does not bog down like it does with the airfilter installed.   

[slowjo]

The weather for Northeast Ohio for the next 4 days is RAIN! So I'll have plenty of down time to play around with it. My friend has a set of pods that he said I could  use. Maybe the unrestricted flow of the pods with the rich running condition of my bike will balance it out?

[nancy]

I would suggest that maybe u should NOT be running the clips in the stock position - as u have 4-1 (right?) - not stock. In any case, over the years with wear and tear etc - stock sometimes doesn't cut it. I have stock 4-4 exhausts and jets for my K1 generation engine - it had rich sooty deposits on plugs. Changed my needle clip position on 3 of my carbs to make them nice and grey and left my no 3 at stock height as that cylinder was not sooty. Go figure...
Regards
Mark

[slowjo]

I'll try the pods first, if it doesn't help I'll move the clips. What clip position would be best? I know that every bike is different,  I'm just trying to get some ideas on what to do next.

[nancy]

Slowjo...if you're rich and sooty...and decide to try the needle clip change.. the needle needs to move down..so the retaining clip needs to move UP a notch... The stock position is 3rd or middle...on my generation bike...K1,2,3... So they will end up in the 2nd slot from the top or blunt/fat end of the needle. In other words you need to reduce the amount of fuel entering from the bowl. The lower the needle is the leaner things are.
I'm happy to be corrected of course..and frequently am!
mark

[slowjo]

I just took off my airbox to see what would happen. If its running rich now, would running the bike without a airbox lean it out? Just for a few minutes. The answer is no. It still smoked a little when I revved up the idle, and spit a little gas out the pipe. I might try to move the needle clip this weekend.