Topic: 74' CB550 Running issues.

[74CB550CafeNick]

Hey everyone, new to the forum and a new and proud owner of a 1974 Honda CB550. Bike looks great, just need it to run right. First the need to knows: New plugs, oil, Filter, chain and Battery this last weekend. Bike was gone through/tuned in 2013 last including being updated to Accel Electronic ignition, with pod filters and Mac 4 into 1 exhaust, jetted/synced to that. Last owner put on maybe a couple hundred miles since he purchased in 2013. Stored in heated Garage, stored with stabil during winter. Issues: Rough idle/run lack of acceleration under 3,000 RPM, and will barely hit 6,000 rpm and maxes out about 70 mph and just does not have anything more. I have been running seafoam in the tank with 93 octane Premium grade gas for about 25 miles (Maybe need more miles to let it work). Has spark to all cyls. My assumption, being new to this, is that the carbs need a good clean. Will listen to ANY help. New beautiful bike and I want to be happy, but the running issues have be down. Thank you in advance!

[Trad]

Do you know what the carbs were jetted to?

I would check your tappet clearance. .002" intake .003" exhaust. Then double check your ignition timing.

Once that's done pull your carb rack and do a thorough cleaning.

Is the bike hard to start? do you notice any spitting from the intake filters or backfiring from the exhaust?

[74CB550CafeNick]

The bike is hard to start when cold, 36 degrees here this morning, killed the battery had to pop start it after kicking didn't work, took about 45 minutes. Some minor backfiring nothing majorly noticeable, mostly slowing down/backing off the throttle. Between 3,000 and 5,000 pm she purrs.

[Tews19]

Hey are you in WI? I've seen that bike on CL for a while. If you are in WI. Feel free to hit me up. I'm in waukesha.

[Tews19]

Do a full 3k tune up. Never believe the previous owner. Many members will tell you that here. Backfire or popping on decel? I bet the bike needs the carbs cleaned and rejetted. What did the PO say he changed the Jets to?

[74CB550CafeNick]

Yes I am in Wi, in West Bend, Yes it was on CL for a while, guy WAS asking way too much, we changed that. Custom built from Combustion Cycles in NC. Clean bike for the age, just the killer is how much it has been ridden in the last 2 years, which is very little.

[74CB550CafeNick]

Unk what the previous owner jetted too as it was built by a company out of NC, I contacted them as it was some time ago all they could tell me is that  it was one of the better running 550's they had in. A friend of mine test rode it before purchase and said the same, since then the gas was run out and it runs poorly. And it lightly pops when slowly.

[Tews19]

Ah cool. West bend has some nice back roads for riding. Can you upload a video of the bike running?

[Tews19]

Popping on decel means it's lean. May have to drop the needle to the 4th notch on each carb. May have to clean the carbs if you rode till wmpty. May have debris in the jets. 

[74CB550CafeNick]

So low grade, 87 octane is fine to run? I just filled with Premium this morning. I will not add any more Seafoam, though I have had a lot of advice TO run it. I am going to attempt to remove the bank of carbs this weekend, looks easy enough and do a "quick clean" and to familiarize myself with it. Just soak em down in carb clean, remove bowls and check floats, not sure how in depth I am comfortable with from there. 

[74CB550CafeNick]

Never took a carb apart, or where the emulsion tube even is, but my plan is to remove the bank this weekend and take a look at it all and see what I can see I guess, unless Tews wants to make a house call! LOL

[sinister902]

Cal hit all the right nails.

beyond that, the MAC system shouldn't really influence jetting past the stock sizes, but the pods surely do. When I had a 1975 cb550 and Uni pods on it, I ended up with 40 pilots and 118 mains, and forever played with needle clip position trying to dial in the mid range. I ended up giving up on it and just dealt with a somewhat choppy mid range. In my experiences, the 77-78 carbs responded far better to pods and were much easier to tune for rideability.

[74CB550CafeNick]

Yeah mine is upper end range, and lower end when riding , mid range is great, just gotta keep it there.

[Deltarider]

Do not run 93 octane in your bike, its too high for the ignition and valve train to properly combust

I don't know where you got that 'wisdom' from.
Could there be water in the fuel?
Some popping on decel is not uncommon after a long period of sitting.
I read there's an electronic ignition so we can rule out a faulty condensor.
Sure about the timing?
Carbs can be cleaned without removing the rack. Remove the float bowls and all jets are accessible and can be removed, even the needle jets (aka emulsion tubes). Once you've removed the floatbowls I recommend to change the 16 screws for little allen bolts. They're much easier for future removals if needed.

[DaveBarbier]

You also mentioned the chain was replaced. Chains and sprockets should be replaced together. If you put a new chain on worn sprockets the chain will wear quickly as it mimics the sprocket's wear.

As far as cleaning carbs, with pods it's super easy to remove the carbs. Remove the pods, fuel line, throttle/choke cables. I unscrew the two manifolds from the motor (10mm nuts) and remove with the carbs as opposed to wrestling with the surprisingly strong rubber boots. Just make sure the o-rings between the manifolds don't get pinched when reinstalling.

And don't do just a quick clean. Clean them so you're 100% sure that's not the issue. It sucks to second guess yourself and think you could have gone further if the problem persists. And don't clean them on the bike, it's much easier to spray carb cleaner while having the rack in your hands. Oh, and when spraying in the jets and jet's galleries in the carb, WEAR SAFETY GOGGLES! Carb cleaner burns badly!


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1978 Honda CB550K

[Deltarider]

Aaahhh... 'numerous studies'. I could have known.
Calj, I'm sorry but it is crap, nonsense. It is fought before in this forum and not only by me. It is no use debating with those that can't tell detonation from burning.
Mark Twain... he was an expert on engines... steam engines to be precise. Read his Life on the Mississippi. It's one of my favorites. The Innocents Abroad is another one. I used them both when I gave classes in writing and when we were on the topic of Irony. The Innocents abroad... I like that title more and more.