1983 CB650 bogs at 4K rpm then goes

[Handyman1018]

Hi, new to the forum, seeking some guidance.

1983 Nighthawk CB650.  Bike was running great but now when I am accelerating the engine momentarily just bogs down right around 4K rpm.  If I stay on the throttle and count in a few seconds it takes off like a bat out of hell.   This "bogging" does not happen all the time (maybe 50% of the time) so I don't think it is fuel related?  BTW I have cleaned the fuel filter and rebuilt the carbs a couple hundred miles back.  Have also run a can of seafoam and heet thru a couple of tanks of gas.  Bike currently has 23K miles.   

Appreciate any comments. 

Thanks!

[ak85lp]

I have an 1982 that did much of the same. I found a post online for an older CB650 that suggested taking off the cover that holds the air filter in and just keep the filter attached with washers. Worked for the most part for me. Also I have heard that the tube that hangs out around the center stand may need to be drained.

http://www.myhonda650.com/cb650problems.htm

[Handyman1018]

Thanks so much for the suggestion.  Unfortunately the air filter on the 83 CB650 is structured so that if I did mess with the air box cover (e.g. installing washers) it would allow unfiltered air to be fed to the carbs.  Still you have given me an idea that I will just loosen the airbox cover and see if this solves the problem... if it does I might just need to replace the air filter (I have no idea of the age of the air filter).   

Curious when yours bogged down did it do so only momentarily (like for a few seconds)?  It does not make sense to me that if air flow was the issue that it would go away by simply staying on the throttle.  javascript:void(0);

Again appreciate any comments. 

[biometrics]

This site, which I found using the link in the previous post, also has the entire Pre-1982 CB650 Honda Service Manual available on line, one page at a time. 

http://cosky0.tripod.com/

[ak85lp]

It would bog right down and then with just a minute twist of the throttle it would pick up again. My issue was not the exact same, but just to give you a few ideas.

[Laminar]

This site, which I found using the link in the previous post, also has the entire Pre-1982 CB650 Honda Service Manual available on line, one page at a time. 

http://cosky0.tripod.com/

But all of that is irrelevant to you, since the '82 and '83 are completely different.

http://www.amazon.com/Honda-Cb550-Nighthawk-1983-1985/dp/0892874201/ref=sr_1_1?s=gateway&ie=UTF8&qid=1285601692&sr=8-1

There's the Clymer's manual. You can search through it on Amazon's site. If you're looking to buy a manual, get the official Honda version if at all possible.

Please describe your process for "rebuilding the carbs."

Is your air filter new/recently cleaned?

Are your spark plugs new?

In what condition are your plug wires?

[Handyman1018]

I used the rebuild kit for my carbs.  Cost about $80 for all four.  Included float gasket, float needle and a few o-rings.   I took the carb rack off the bike, and worked on each carb individually removing the bowl, cleaning out the gunk, used a fine copper strand of wire to clean the jets.  I did not dare separate the carbs from their rack.  I think I did everything correctly and the bike was running fantastic for a couple hundred miles before the bogging started.  I do have the clymer manual. 

Bike has new spark plugs.  The plug wires look to be in good shape but are likely original to the bike.

Air filter cleaned with compressed air but it too is likely original to the bike.

Do you suspect an electrical issue or maybe the main jet is hanging up?

Thanks.

[Laminar]

Do you suspect an electrical issue or maybe the main jet is hanging up?

It really could be either. An intermittent issue like this is so hard to pinpoint. It sounds like you did the cleaning correctly, but you don't have to be scared of pulling the carb rack apart, it's not bad at all.

The first suspect is always the carbs, as it's so easy for a speck of dirt to get in there and ruin everything. Another possibility is bad insulation on your spark plug wires - this can be checked by running the bike in a dark garage and misting the plug wires with clean water from a spray bottle - listen for crackles and watch for arcing between the wires and any ground such as the valve cover or head.

Also try and remember the conditions each time this happens - are you at a particular fuel level? Is the engine always cold or always hot when this happens? Is it always right after a long stretch at high speeds?

[Munkey]

I suspect the plug wires. Old wires will leak voltage through the insulation to the shortest path to a ground. This will mostly show up under hard acceleration. They are not very expensive to replace. If they are original, then they are WAY overdue to be replaced.

[ak85lp]

They are not very expensive to replace. If they are original, then they are WAY overdue to be replaced.

Munkey is right. I took a complete wire off my bike into an automotive store. The plug boot looked the same after I went through a few boxes of Champion wire sets. Some wires were too long so I just cut them off and refitted the boot that goes to the spark plug. Total cost was around 20 bucks.

[Handyman1018]

Excellent ideas, thanks

The bogging happens weather hot or cold, gas tank full or not, and the intermittent nature of it has me leaning to electrical.  Agree the wires are over due for an upgrade and with your suggestion I can keep the cost reasonable.  So after some testing will likely go with new wires first and if that doesn't do the trick I will go back to the carbs.   Will report back soon as it stops raining up here.   Stay tuned. 

[Handyman1018]

Rain finally over here in PA.   Took the gas tank off and unplugged and cleaned the connections to/from the coils and removed/inspected/reconnected the original plug wires.  Specifically I noticed the secondary connectors on the coils were really badly corroded.  Hit them with a small wire brush till they shined.   Power drop off is GONE, and I am back on the road.  Another no cost fix on the NH thanks to the forum members!

[Laminar]