I just picked up an 87 CBR 600F and am trying to get it running. It's really lean when running on the pilot jet, even though the carbs have been rebuilt and cleaned multiple times. Is the air box supposed to be full of 1" holes? I'm guessing this must have been a "speed" mod back in the day and the bike was never properly rejetted. I'm at 500', any pilot jet size suggestions?

 

The holes in the box, if they are located at the top, under the gas tank, are part of dyno jet's stage 2/7 jetting instructions. If you do not have the dynojet adjustable needles and jet sizing kit, you will be lean no matter what. The stage 2 kit comes with like 40 jets in multiple sizing for both main and idle.

 

You need to verify what jets you have in the carbs.


It would also help if you posted what mods are on the bike like pipes, air filter, etc.