Topic: CB550K Loses Electrical Power in Upper RPMs

[VigCS]

Hi all,

I posted this in my other thread about jetting, but figured I'd start a new topic to get more exposure.  My CB550 is having an odd electrical symptom.  When you hold the throttle wide open it'll rev up to around 6,500 rpm and seemingly lose electrical power.  The exhaust will crackle and pop, and as soon as you let off the gas the power will come back and it will go back to idle.  This has been thoroughly confused.  Here's a video of it happening:

Any ideas?  Thanks!

[b52bombardier1]

Very bizarre.  Do you have a multimeter?  Connect it up to the battery and run a few DC and AC voltage measurements there with the bike running at idle and at that high rpm speed.

What does your meter say at those points?

Rick

Sent from my SAMSUNG-SM-N900A using Tapatalk

[BomberMann650]

At first i thought "points bounce" maybe...then I saw the indicator and headlight do that thing...yikes. 

Motor sounds good otherwise.

I'm with b52, suspect vreg and rectifier are getting out of whack once the stator/fc start ramping up.

Which reminds me, I should probably dial back my omp vreg some too...headlight wants to oscillate at upper rpm too...but it hasn't limited my revs like that...

Hmmm.

Are you using oem points breakers?

[VigCS]

At first i thought "points bounce" maybe...then I saw the indicator and headlight do that thing...yikes. 

Motor sounds good otherwise.

I'm with b52, suspect vreg and rectifier are getting out of whack once the stator/fc start ramping up.

Which reminds me, I should probably dial back my omp vreg some too...headlight wants to oscillate at upper rpm too...but it hasn't limited my revs like that...

Hmmm.

Are you using oem points breakers?

Yes, they're OEM breakers as far as I know.  I've got an extra ignition plate as well (with new points, condensor, etc...). 

Would a voltage regulator or rectifier getting out of what cause loss of power at RPM, or excessive power?  Or both, depending on the situation?

I'll give the exercises you guys suggest a try tonight and report back.  Thanks!

[seanbarney41]

I notice there is no key in the key switch...so you must have bypassed it somehow.  Are you sure you have done this correctly with good tight connections?...cause it really sounds to me like engine vibrations are disturbing a loose connection.

[Deltarider]

I notice there is no key in the key switch...so you must have bypassed it somehow.  Are you sure you have done this correctly with good tight connections?...cause it really sounds to me like engine vibrations are disturbing a loose connection.

That was my first thought too.

[VigCS]

I notice there is no key in the key switch...so you must have bypassed it somehow.  Are you sure you have done this correctly with good tight connections?...cause it really sounds to me like engine vibrations are disturbing a loose connection.

The ignition barrel recently broke - the glue on the little plastic rotator piece that fits inside the key barrel broke.  The plastic piece is underneath the key and I was just rotating it to the ignition position - but that may be worth checking out.  I need to order a new one. 

I also tried it again last night and, of course, couldn't reproduce the problem.  I did recharge the battery in the process, though, so maybe the battery was just weak?  I also checked voltages revving it up.  It was getting to 12.9 - 13.0 v at 3,000+ RPM (which honestly seems a little low). 

[VigCS]

I'll check again tonight, but I checked it through the rev range up to about 7,000 and never saw higher than 13V.  I may try another volt meter just in case since I was using a crappy harbor freight one.  Here's a video of me checking the voltage:

Looks like it doesn't go past 12.84V in that video, and I definitely revved it past 5,000.

[seanbarney41]

I would assume that key switch is the vast majority of your problem.  It is easy to bypass for checking, then check your charging system.

[VigCS]

I would assume that key switch is the vast majority of your problem.  It is easy to bypass for checking, then check your charging system.

I guess I'm not quite understanding how it can be a problem.  Are you thinking when it revs the vibrations jiggle it such that it's momentarily cutting the ignition out?  Either way, it seems like the charging system isn't putting out quite enough juice...

[BomberMann650]

I would assume that key switch is the vast majority of your problem.  It is easy to bypass for checking, then check your charging system.

I guess I'm not quite understanding how it can be a problem.  Are you thinking when it revs the vibrations jiggle it such that it's momentarily cutting the ignition out?  Either way, it seems like the charging system isn't putting out quite enough juice...

Yeah, bad vibes would make an intermittent short.  Its worth checking the connections anyway.  A simple loose connection could undermine the results of other charging system tests. 

[seanbarney41]

I guess I'm not quite understanding how it can be a problem.  Are you thinking when it revs the vibrations jiggle it such that it's momentarily cutting the ignition out?  Either way, it seems like the charging system isn't putting out quite enough juice...

I too don't think a bad ignition key is preventing your charging system from reaching its potential. More than likely, you have a loose ground or corroded connection somewhere thats not returning charge status back to the battery.

It sounds as though you might need to perform some diligent maintenance on your entire wire harness, electrical connections, and charging components.

yup