Topic: 74 CB 550 woes

[yooperlou]

Need a little help here, this bike is driving me nuts. When the bike is cold it runs/idles great. When it heats up it starts to miss, buck on what seems to be number one cylinder, (coming from left pipe).  I put in new points/condensers, coils, plugs etc and it still doesn't go away. I rebuilt and synced the carbs prior to this. I believe  it is electrical in nature because the fuel system is working flawless. Does anyone know where to go from here? I did time it using the static method not a light. Wonder if I received bad points? I'm lost and tired of replacing parts most likely not needing replacement. Any help would sure be appreciated. Thanks

[yooperlou]

Follow up question...could a sticky valve cause this?  I did have to adjust the valves, although minutely but I did tinker with them.  Thanks again.

[750goes]

A sticky valve could cause your problem, but from what you describe it could still be fuel, electrical or air related..

It could be a bad spark plug cap, clogged idle jet, not enough fuel, timing too advanced - do the 1 & 4 pipes run hotter than 2 & 3 ?

Is the air filter clean ??

clean or run through the points with a alcohol cloth (ignition off)...

[yooperlou]

Thanks for the reply.  The plug wires/caps are new, the carbs have been completely re-done two days ago, the timing I'm not so sure about because I never put a light to it.  Now that you mention it one and two seem somewhat cooler than three and four but I only did the "spit" test on the pipes with my finger after it cooled for a while    At the moment I'm not using an air cleaner, waiting on pods, although I don't think not using a filter is the problem.  When we first started this little project this was the major problem we have been dealing with no matter what we do, doesn't matter if the filter is in there or not. I'd put it back but my hands look like hamburger trying to get them damn boots on.  Thanks again.

[750goes]

I just replaced my air boot clamps, they were 30 years old and I could not tighten them up enough to secure the boots in place..

went to the local hydraulics franchise and bought eight new clamps, that I could do up with a ratchet driver.

apart from getting them on (while carbs were still on the bike (my hands are the same)), I got them in place and tightened down firmly, and my bike besides a few other issues - stopped backfiring....and it even ran a bit smoother when I put the pods on...

with no filter it will possibly backfire a little bit and run lean - causing HOT exhaust.....just a thought anyway...

[yooperlou]

the problem I have is when the carbs are on the only way to get the boots on is thru the air box.  Sharp s.o.b. to put it mildly.  There is no way that I can see to put the boots on any other way.  It's impossible to put the carbs on with the boots then put the airbox in.  Just won't fit that way because of the frame. The boots themselves are still quite flexible and the clamps aren't bad.  Am I missing an easier way to get these suckers on?  I really don't want pods but I'm not going thru this crap every time I need to get at the carbs.

[750goes]

Sorry,

I misunderstood your comment regarding the rubber boots, I was talking about the boots between the head and carb bodies, not the other side, also was in relation to a 750F not a 550...

there was a mention some time ago of how to mount the airbox/rubbers on the 550 and how to get enough learance, try and find it for you...

 

[750goes]

here is the text

I managed to get the carbs back on my CB500 without too much trouble...I assembled everything on the bench; carbs, isolators, manifolds & clamps...left the airbox boots off, stuck the airbox over the carb inlets, and pushed/twisted everything in place...snugged up the manifold nuts, pushed the airbox back against the frame, inserted the airbox boots into their respective holes 1 by 1, folding them to get them on the box first, then push over the carb inlets...no cussing, no breaker bars, and a minimum of skin lost (hey -  it grows back!)...not a fun job, but do-able...

Only problem is, now my carbs are slow/sticking again...argh!!!...

[yooperlou]

here's another thought out to the wind.  Could a fault petcock be causing this.  Never really thought about it until now.  While synching the carbs I pulled some gas from the tank, which was off the frame, and put it into my auxilary test tank.  For some time both tubes were giving gas freely then one side just stopped.  I remember now that some time ago while working on a kawa kz that I was told that during the run position only one side should work and only both sides should pour when in the reserve position.  Is this true with Honda's?  Just thinking out loud here, really frustrated I can't figure this out.  Thanks 750 for the replies, appreciate the help.

[750goes]

That's pretty simple to check--- just open the fuel tap with a container underneath it, and run it through all positions, and see if one way or the other shows some blockage - should be simple to fix as well if that is the problem.

let us know what the result is........hopefully no contamination issues

[pmpski_1]

I feel your pain about the boots from the airbox to carbs. I haven't found a better way. Luckily the carbs are ok and I only had to do it twice before I got it right.

1 - 4 and 2 - 3 fire at the same time. Not 1-2 and 3-4.

What makes you think it's #1? Also, why do you think it's electrical? I'm not saying that it's not, but you've replaced coils, points, condensors, plugs etc. You mention that the fuel system is working flawlessly - what configuration is causing the problem, with pods or air filter? If you use pods instead of the air filter you're gonna get different results.

I didn't have the patience for points and replaced them with a Dyna so I can't really comment there, but you should double check your timing. And valve clearances.

[clarkjh]

For some time both tubes were giving gas freely then one side just stopped.  I remember now that some time ago while working on a kawa kz that I was told that during the run position only one side should work and only both sides should pour when in the reserve position.  Is this true with Honda's?

You need fuel in both lines, one line goes to 1-2 the other 3-4, when the one closest to the bowl on the petcock is full it will overflow into the second and fill that line.  If you are not getting enough fuel through the petcock it will only feed one set of carbs in the "Run" position and will starve the other two of fuel.
When you cleaned your carbs did you install "In-line" filters?  If not it could still be a carb problem.  Also, once you get use to taking the carbs on and off more the thrice it gets easy.  Big thing is take your time and have patiance you will get it.

James

[yooperlou]

Thanks everyone I'll try to answer some of your questions.

When I say my fuel system works "flawlessly" that is just my assumption.  Everything appears to be working according to the vacuum gauges, etc.  I used to be carbing up the left pipe, fowling plugs, but it runs nice now, no burning rich or anything like that.  At the moment I have neither pods or the airbox installed.  With or without the airbox/filter makes no difference.  The problem comes either way.

When I did the carbs I didn't put in-line filters on, probably should have though.  My thoughts are turning to the petcock.  I will check that out before work today and see what develops.  With all the new electrical items it's starting to look more and more that it is a fuel related problem.

Just out of curiosity how does everyone like their Dyna's?
Thanks again.

[brad weingartner]

Unrelated, but where in Upper Michigan are you? I'm in Ishpeming with a CB550.

[Bob Wessner]

Continuing as unrelated, though we are "trolls," my wife and I love the U.P. Annually we go to Lake Gogebic.

[bryanj]

I know you have done it but you need to start at the begining and check that the points gap is 14 thou with the timing set atthe "F" marks for the relevant side. NOTE:- altering the timing WILL alter the gap so it takes some time and practice to get both right at the same time. Then recheck the tappet clearance and adjust the camchain after all that its worth re-checking the pilot jets and jetways whilst fitting inline filters after cleaning the petcock.
Having done all that then chen the carb balance with gauges.
As this occurs when hot i would suspect either not quite correct points; Plug or cap; jetways in carb

How did you change the plug wires as they are bonded into the coils? and are you using D7EA plugs --NOT DR7ESL.

As to the boots It is possible to fit the air cleaner box complete with boots and, with the inlet manifolds and rubbers fitted, get the carb bank in and onto the manifolds then the intake boots. I know it aint easy but with new insulators, (rubbers on manifols) that cost about £10 plus shipping for a set from Dave Silver, its not too bad. Also Dave noe sells just the rubbers for the airbaox at £18 a set. Both of those plus tax in UK and shipping

[yooperlou]

Thanks Bryan, good advice and exactly what is on the schedule.  My hopes of something as simple as the petcock went away today.  Going to start ONE more time from scratch and see what develops.  Thanks everyone for the excellent and fast feedback.  Best site for vintage bikes I have come across yet.  Brad..very cool I'm on Deer Lake Road.  Not sure but I may know you, the name is familiar.  Do you have the gold bike I see cruising from time to time?   I have the sandstone house on the sharp curve right before the carp river, the camper and at least one jeep will be in the side yard, swing by if you see me in the garage and have a brewski. I'm afternoon shift for a couple more days then midnights so having an eyeball and bs'ing may be difficult for a few days, send me a PM or email me I'd like to talk with you.