The All Too Common Bogging Down

If it's broken or just needs tweaked

Moderators: Volker_P, tidd650

cattman42
Posts: 14
Joined: Sun Jul 10, 2016 10:01 pm

The All Too Common Bogging Down

Postby cattman42 » Tue Apr 11, 2017 12:27 am

Hello everyone, I have a 1981 cb650c with ~ 36,000 miles on it.. The pipes were changed from stock to 4-2 straight pipes, no baffles..I am running it without the airbox cover (I've tried with, too, same result) with a k&n air filter.. The bike starts fine, and idles great.. however, in all gears, it bogs down right around the 6500-7000 rpm mark, it will NOT get passed 7k under load. if I pull the clutch in the bike gets right to red line with out any problems.. To describe the way this sputtering sounds, it spits in and out and will continue to do so from 3/4 - full throttle (at 6500 rpms) until I release the throttle enough for it to breathe.. the bike can cruise at about 65, 70 is when it starts having these problems, will not get passed 75.. I'm not sure what size jets it has, as I'm trying to avoid digging into the carbs.. spark plugs are looking carmalized, just a tint of brown. Any and all advice is appreciated, thank you!

cattman42
Posts: 14
Joined: Sun Jul 10, 2016 10:01 pm

Re: The All Too Common Bogging Down

Postby cattman42 » Tue Apr 11, 2017 12:32 am

I forgot to mention, my bike back fires (very slightly) at idle, and even more so at the high rpms in deceleration

User avatar
Folsoml
Posts: 1351
Joined: Sat Apr 07, 2012 9:02 pm
Location: North Florida

Re: The All Too Common Bogging Down

Postby Folsoml » Tue Apr 11, 2017 12:56 am

Dig into the carbs. The problems you describe could be a couple of things, but the carbs are the most likely. How is your charging system? If your charging system is not working properly, it can cause these problems as well.

Your backfiring problem is likely an airleak in your exhaust system--probably near the head. I would wager that whoever swapped out the original system for the exhaust that is on it now did so without using new copper gaskets. They are not reusable, and will cause air leaks if you try.
Have a problem with your CB650? Have a technical question? Click here!

Want to know how to post pictures? Click here!

My Current Bikes: 2005 HD FLHTCUI Electra Glide Ultra Classic, 2007 Yamaha Vino,

cb650
Posts: 2902
Joined: Fri Mar 03, 2006 7:20 am
Location: Denver CO USA
Contact:

Re: The All Too Common Bogging Down

Postby cb650 » Tue Apr 11, 2017 4:43 am

check the pulse generator air gap to. easy check. I bet the jets are to fat too.
Did you clean the tank out?!?!?!?!

cattman42
Posts: 14
Joined: Sun Jul 10, 2016 10:01 pm

Re: The All Too Common Bogging Down

Postby cattman42 » Tue Apr 11, 2017 9:52 am

Thanks for the responses guys, the charging system seems good, however I haven't tested it, what is the best way to? I think I recall the guy I bought it from saying it still has stock jets, with straight free flow through the exhausts could it be needing larger ones? Also, it does have an exhaust leak right near the head, you nailed that.. only on the rightmost exhaust, it seemingly goes away after the bike warms up, is this something that could damage the bike?

User avatar
Folsoml
Posts: 1351
Joined: Sat Apr 07, 2012 9:02 pm
Location: North Florida

Re: The All Too Common Bogging Down

Postby Folsoml » Tue Apr 11, 2017 1:38 pm

To check your charging system, make sure that your battery is fully charged. Hook a multimeter to each terminal on your battery. It should read about 12.7 volts at this point. Start the bike and rev it to 3000 RPMs. The reading should go up to 13.5 to 14 volts. Note: This engine is air cooled, so make sure you do not have the engine running for more than a minute or so without have a couple of large fans blowing across the engine.

You are really going to need to clean those carbs.
Have a problem with your CB650? Have a technical question? Click here!

Want to know how to post pictures? Click here!

My Current Bikes: 2005 HD FLHTCUI Electra Glide Ultra Classic, 2007 Yamaha Vino,

flatlander80
Posts: 12
Joined: Fri May 05, 2017 9:08 pm

Re: The All Too Common Bogging Down

Postby flatlander80 » Tue May 09, 2017 8:07 pm

Any time you have popping on deceleration you more than likely are running lean. Opening up the pipes and running without the airbox will lean out these bikes. As well, and passages/jets in your carbs that are plugged, or air leaks on the intake side will cause the bike to run lean...


Sent from my iPhone using Tapatalk


Return to “Technical Discussion”

Who is online

Users browsing this forum: Bing [Bot] and 9 guests