Topic: 1976 honda cb750f supersport. cylinders 1 and 3 are lean 2 and 4 rich

[cado007]

1976 honda cb750f supersport. cylinders 1 and 3 are lean  2 and 4 rich

so I have a 1976 honda cb750f supersport when I got it it was rough and I cleaned the carbs and used a 4 into 1 kit. The needles were shot so I used the kits needle. It was running good but rich on all 4. So I put the needles on slot 2 from the top instead of 3 and still rich. The 4 into 1 kit came with 38 slows and 105 mains. I bought new oem needles and reinstalled original kehin 40 slows and 105 mains and now 1 and 3 are lean and 2 and 4 are rich. I adjusted 1 and 3 cylinder air screws to 2 turns out and 2 and 4 to 1/2 turn out and that helps but this seems really weird. Maybe PO did something to jets. Has anyone ever encountered this. Should I buy new Kehin jets all around and try again. These are 064a roundup carbs with Mac 4 into 1 exhaust . I vacuum synced them and it idles well. I am just worried about the lean ones although they are 20 degrees cooler than other 2. Thanks in advance. also I have only gone about 20 miles so far to check the plugs.

[Jerry Rxman Griffin aka MuthaF'er]

Double check your float levels??

Rich/lean at what ranges?

[HondaMan]

Are the hose clamps on the carbs (or at the head) all the way closed up when the screws are tight? the hoses may well be shrunk by now, so the clamps don't seal them very well. This requires new hoses, usually. Alternately you can try the Oetiker clamps #050-09 here:
https://www.aircraftspruce.com/catalog/appages/oetiker.php?clickkey=23818
but do be sensitive with these, as they can easily be tightened too far, cutting the hose right off! (Don't ask...).