Topic: 1981 cb 650 running lean?

[tdtravis80]

Hi I recently was given a 81 cb650 and the previous owner cut the baffles off of the exhaust and it is not running right.  when you start it up it blows alot of smoke out of the exhaust and wont stay running even when the choke is pulled all the way out . Im pretty sure it is running really lean right now due to no back pressure on the exhaust anymore. any ideas on how to fix this problem? your input is appreciated!

[scunny]

put a temporary restriction on your exhaust and see if it improves.
smoke could mean running rich, pull the air filter and again see if it improves

[Frankenkit]

first off, clean the carbs. Even if you think they're clean and the PO says they're clean, they're not.   Pay particular attention to your idle circuit. I think even on the 81s, they're pressed in jets.  Someone will either confirm or correct that statement, though.  

We also need to know what color of smoke this is.  Are we talking white, water vapor smoke, black sooty rich-burning smoke, or blue-grey oil smoke?  If it's the latter, you might have valve seal problems affecting your compression and making your bike run 'rich' burning that oil.

Without the baffles, and because 650s are hard to tune carb-wise, you have a couple options.  Some of the guys here have been able to run straight pipes on their 650s with carb jetting.  I'll let them be the pros there.  The other option is to find a stock exhaust or an aftermarket 4-1 to provide some backpressure.

[tdtravis80]

I believe it a is more of a blueish gray but the p.o. said it was running fine before he cut the baffles off once he did that it went to hell. I really dont feel like putting a whole lot of money into this bike (new exhaust) so if you have any ideas on how to fix this cheap im all ears thanks!