1981 CB650 Pilot Screws Adjustments

If it's broken or just needs tweaked

Moderators: Volker_P, tidd650

CBDCL
Posts: 14
Joined: Sat Apr 11, 2015 2:17 pm

1981 CB650 Pilot Screws Adjustments

Postby CBDCL » Fri Aug 28, 2015 8:26 pm

Carbs on this model can be a headache. You already have pressed recessed slow jets making cleaning hell. So perhaps anything helps us unfortunate carb owners.

Most of my trouble was in finding answers online, so I thought it would be nice to contribute pilot adjustments to help perfect your mixtures. If you have different direction, please share.

The factory / initial setting is 2 1/8 out from lightly seated. Rollin in this setting has you running lean. If your ride has a delayed acceleration or surges / stutters, you're probably running lean and need to rich your mix by going out. But this is the factory setting, where you start. Get a pilot screw tool to do this, unless you want to burn the shit out of your hands. Not fun. Been there. You also need a detailed tach. I didn't have this luxury but it's absolutely necessary.

1. Heat bike, ride 10 minutes, stopping and going.
2. Set to factory setting; 2 1/8 turns out
3. Adjust the idle screw getting to the ideal idle speed; 1,050 RPMs +/- -100
4. Turn each pilot screw OUT 1/2 turn. If speed increases 50+ RPMs, continue to turn each a 1/2 turn OUT until speed decreases by 50 RPMs.
5. Repeat step 3.
6. Turn IN pilot on carb #1 until speed drops by 50 RPMs, then turn it OUT one full turn. Then repeat step 3.
7. Do step 6. For carbs 2, 3, and 4.

Test ride and response from idle should be rapid without hesitation.

Hope this helps someone.

Rakestraw
Posts: 1
Joined: Thu Jun 15, 2017 9:05 am

Re: 1981 CB650 Pilot Screws Adjustments

Postby Rakestraw » Thu Jun 22, 2017 2:09 am

CBDeCL wrote:Carbs on this model can be a headache. You already have pressed recessed slow jets making cleaning hell. So perhaps anything helps us unfortunate carb owners.

Most of my trouble was in the Instant Knockout answers online so I thought it would be nice to contribute pilot adjustments to help perfect your mixtures. If you have different direction, please share.


Thanks for the super helpful guide CBDCL!


Return to “Technical Discussion”

Who is online

Users browsing this forum: Bing [Bot] and 20 guests