Topic: '82 CB650SC Intake tuning tips

[NateTheBookie]

Hey All,
   I have an '82 Nighthawk with a 4-2 Vance and Hines system, the PO had put some pods on it, but that caused it to have huge flat spots in the acceleration curve. I've replaced the stock air box, and it runs much more smoothly at low RPMs, but chokes and loses power past about 75 MPH on the freeway. I read somewhere that if you take off the airbox covers and just use Fender washers to hold the air filter in on the CB650s it really improves their performance, so I tried it. The performance on the freeway now is great! it pulls strong all the way up to redline in top gear and easily tops out my speedo at 85 MPH, but it's performance around town suffers, and lower RPMs feel very flat. Is there a way to tune this so I can have both the linear throttle response at low RPMs, and good power on the freeway? I was thinking about leaving the airbox cover off and then running the idle jets super rich (2 to 2.5 turns out), do people think that could work? Or is there a better trick to get good performance out of these old 650s that I don't know about yet?

[trueblue]

Make sure your emulsion tubes on both your idle jets and main jets are clear, if they are clogged, which is common, it will cause bogging and flat spots.  On the 82 the idle jets screw out just take a little care when removing them, it is easy to damage them, you need to use a small flat blade screwdriver, just make sure it is a really good fit before cranking on it. The emulsion tube for the main comes out with the 7mm hex just above the main jet.  Another thing to consider is your ignition advance mechanism may be stuck, also quite common, but usually only cause problems at the top end of the rev range.