A friend of mine recently received a CB900C which has 4 into 1 exhaust. No history of the bike is known. It had a fuel leak so we installed 4 new carb kits but left the jets which were installed. There were no numbers on the jets. The bike starts easily and idles fantastic. We can rev the engine with no load and it revs with no issues. The current fuel mixture is 2 full turns. As we take it for a test ride the bike is popping/sputtering some until 4000 rpm which is when it bogs down. I assume the jets and needle are stock size. From what I have read the jets are primary - 68, main - 105, slow - 35 or 38. My guess from reading is that the main jet needs to go to about 125? Can anyone help confirm what jets and needle this bike needs with a 4 into 1 exhaust? The make and model of the exhaust is not known. The air filter is currently stock but my friend is willing to change these to PODs which would make it easier to play with the jets. My thoughts are that the popping/sputtering is lean mixture from the needle and the 4000 big down is the main jet. Help please.
