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[turbobike] CV carb springs

Dave Morrill (david.p.morrill@fairchildsemi.com)
Mon, 03 May 1999 15:15:20 -0400

All,
    Took my CBR600 turbo for it's first ride this weekend.  It's
suffering from 2 carb related probs.  I have a baaad lean spot around
6-8000 rpm, off the guage on my 02 sensor.  If I can get it to cough
through that (scary) it pulls hard and runs OK, but I get a wicked
backfire between shifts (chase vehicle reported 3 foot exhaust flames
before I buzzed out of sight).

    I've been moving my stock needles richer each time and am getting
some improvement in running, but am always full lean at 7-8000.  It
makes 6-7 lbs of boost here and 10lbs above 8000.  Originally, the
slides were opening too fast and flooding the motor at about 3000, so we
plugged 1 of 2 holes in the slides at the suggestion of the mechanic
where we were dynoing.  I think this is my backfire problem, they are
slow to open and therefore slow to close.  So I will be removing the
plug and going to stiffer springs like y'all suggested.

    Where do I get stiffer springs, and how is the stiffness rated????
I'm planning to shim them tonight to see if I can get rid of the
backfire at least.

    Feedback?  I'm thinking I need a different taper needle to fix the
lean spot, but how are the tapers measured?  I made a see through cover
on my airbox, so I know approximately where the slides are at this rpm
under no load.

thanks,
    Dave.