Topic: New to Carb adjustments

[WiredForStereo]

My 1980 CB650 still has serious hesitation to about 3k rpm at all times unless piping hot.  Stock everything but pipes, I believe they are aftermarket pipes, and I doubt anyone has ever done anything to the jets.  Runs well at higher rpm's but may be running lean, I am not sure.  It just seems like it runs slightly better with a little choke.  It idles just fine, never smokes and the plugs look about as good as they can.

What can I do to tune this thing up?  It has slide carbs, can I adjust the needles, do I need new larger jets?  Can I drill out the jets?   If so, how?
Thanks
Sol

[eurban]

Is your acelerator pump working?  Have you adjusted the idle mixture?

[WiredForStereo]

Yes and yes, but the idle mixture's dont really seem to do much.

[AntiRiceCRX]

hey Wireforstereo, my bike does the same thing, not that bad of hessitation but it just feels really weak at low rpm but with lots of throttle at high rpm it takes off.

[eurban]

The mixture screws should certainly make a difference. If your idle jets are not clear, the mixture screws don't properly function.   The pressed in idle jets are a bit of a challenge to clean properly; my personal preference is to carefully pull them and give them a good soaking folllowed by some prodding with a strand of copper wire.  Clear the side holes on the jet too.  Don't waste your time "carb tuning" until you have gotten your idle circuit working properly. . . . .Your main jet needles probably have only one clip position but if you want to richen the mixture you can get small electronics washers from radioshack etc that can be used to shim the needle.  You could drill out your main jets but it would probably be better to order up a set in the size(s) you want. 

[ddmcnair]

Just worked on my 82 cb650 and can let you know what I did.

1.  K&N filter pods (two carbs to each pod).  Had to be modified significantly (with a box cutter) to clear the accelerator pump and the choke.  Also had to cut down the throats since the clearance to the frame is so small in the 650's.

2.  Stock headers and shorty mufflers with a slight baffle

3.  Dynajet kit using the largest main jets and setting the clip three from the bottom on the needles. 

Runs fast and smooth and completely eliminated any stall between 3K and 5K.

Also agree with "eurban" that cleaning the idle jets can be a big deal.  I use a short piece of guitar string and it and it works great.  You can set of the cleaning wires used to clean MIG welding heads - at least for the high speed jet, may be too thick for the idle jet.