Topic: CB550 Rough running

[hereforever23]

I purchased my 1975 CB550K about 2 months ago from a guy who had restored it after it had sat garaged since 1982.  It has an aftermarket 4 into 2 megaphone type exhaust.  It had no major issues when I obtained it.  I made a few changes.  He had installed pod filters with stock carb settings– I installed a used chamber to a bracket fitted with a K&N mono filter.

Yesterday as I rode to work the bike started to sputter and lose power coming off idle at a stop in first gear.  It got worse over several blocks and started idling very erratically and then sputtered to a stop.  When I tried to start it back up with the electric start it wouldn't start.  I had the battery charged assuming that perhaps low voltage was causing ignition issues.  I installed the battery and it started right up but wouldn't idle and died.  Cylinder 2 was cold to the touch.  I pulled the plug on that cylinder and it had carbon deposits, possibly fouled.  While I had that plug out I took a look at the others, too.  Cylinder 1 also had carbon deposits but 3 & 4 looked excellent.  Nice light tan in color. I put new gapped plugs in to Cylinders 1 & 2.  Cylinder 2 is now getting spark & hot to the touch just like 1,3&4.  Still though, the bike idles poorly.  After raising the idle the needle jumps erratically from about 1500-2000 rpm and as soon as I try to pull away from a stop it loses power and sputters out.

Just had a thought as I typed this up...the chamber I purchased on Ebay was pretty clean, but if there were any bits of dirt or anything that I missed it is possible that they would be sucked into the carb jets.  Perhaps this is just a fuel issue?

What would you recommend trying next...should I just bite the bullet and pull all the carbs out and start there next?

[mono]

after re-reading your post, i'd start with the points.  mine are on their last leg and get out of adjustment easily and cause similar probs. 

[Mooshie]

after re-reading your post, i'd start with the points.  mine are on their last leg and get out of adjustment easily and cause similar probs. 

+1 points and then adjust the idle after doing points and timing.  Had to do that to mine this week (adjusted points and timing and bike would not idle>turned the screw and checked throttle cable (it was loose at adjuster nut) and now all is well).  You may also have to look at carbs as stuff could be clogging jets but it is much easier to check points/timing IMO than work on carbs. 

[hereforever23]

Alright I will start there.  Gonna need a tow back...no easy way to get back home from where its parked except a bridge and don't want to die on my way across.  I have a Hondaman ignition sitting here that I haven't installed yet.  I think nows the time
Thanks guys

[phil71]

Did this happen after a rain?

[hereforever23]

It rained earlier in the week but had been driven several times since any rain.  It is always in my garage at night.  Also, I did open the points cover earlier today (did not make any adjustments) and there was no evidence of any water or condensation in there.

[mono]

The hondaman will prob solve future points issues, but you may want to carry a feeler gauge and matchbook in your toolbag with you in case they need adjusting on the road.   

Sent from my SPH-L710 using Tapatalk 2

[WarwickE36]

Ill admit I skimmed your post.  Does it have enough gas?  Is gas getting where it needs to go ... i.e. slow jets may be plugged.  Floats adjusted properly?  Did it run great until you podded it?

[hereforever23]

I have not taken carbs apart but previous owner says he rebuilt the carbs.  He put stock jet sizes in even though he had pods on.  I specifically asked him if he had rejetted for the pods and he said that he had not.  It seemed to run better after taking the pods off and putting a K&N mono filter on.

[WarwickE36]

The stock box will be easier to dial in, a carb sync and proper idle setting will make it run pretty well.  Pods and any other intake mod will require tuning.  I never trust the words of a PO.  He may have rebuilt them but who knows what he did.  He may have used improperly made keyster jets, he may have set floats wrong, who knows where he set the needle position.  Once you determine whether its fuel or spark related you will know youre next move.  If its fuel then you should really either plan on fully cleaning them (every orifice must be clean and clear of debris and varnish).  Nextly, if you plan on running pods you are going to have to play with jet sizing and idle screw settings as well as needle positions.  I recommends getting the manual from this site and familiarizing yourself with it. Especially the carbs and ignition for now. Good luck and keep us posted.

[hereforever23]

Thanks for your reply.
It was running great for the previous 2 weeks that I have been using it with the K&N mono filter installed.  Seemed to be running strong and very smooth at all throttle settings.
I have the manual.  I plan on cleaning & adjusting points and timing tomorrow and working from there.

[phil71]

what you describe sounds like fuel delivery anyway.. It's not the worst idea to look at the points, but I'd check that petcock and screen and check that it flows well when opened.

[Mooshie]

If you are installing HM ignition and decide to put on NEW points (not just gaping and timing your old set) then make certain you let the "goo" on the new points burn off or the backfire and misfires will scare the hell out of you.  I know they did for me.  Mark then informed me to ride it 200+ miles and re-connect his ignition.  Just an FYI.  If using your old points no worries. 

[hereforever23]

I cleaned the points and set the gap but the timing was good.  Still having problems and I think its in fuel delivery.  It gets better mid throttle and up.  I've been busy with other stuff but will keep updating as I make progress. Thanks

[Mooshie]

Sorry to hear it wasn't just the points/timing/idle.  Carbs are a pain IMO.  Good luck.

[hereforever23]

Well on my girlfriend's CB160 its not so bad, they come off really easy.  And to sync them you just hold your hands over the mufflers until you get equal pressure out of each. 
But on the CB550 theres twice as many and they are a real pain to get off with the stock air chamber.

[mono]

Pull the rubber "venturis" first, then remove the airbox.  The carbs will come right out. 

Sent from my SPH-L710 using Tapatalk 2