Topic: hard start, runs like crap when cold.

[Jacob]

77 550k, takes full choke and playing with the throttle to get it to start, then sputters and will die unless you keep giving it throttle. But after 10 minutes or so of riding it settles down and runs good. I set the timing, carbs rebuilt, new spark plug etc. it does burn oil on start up, so maybe  are slightly oil fouled on startup but clear themselves after running?

[Duke McDukiedook]

Umm, what is your question?

Sounds like a normal bike of this vintage, if you are concerned about oil consumption after running through a full tune up you will want to run a dry and wet compression test to see if you have any problems.
 

[flybox1]

do you know where your idle set screw is?
have you adjusted it to help your slow-to-idle symptoms?

[Ira]

My 77 750K is exactly like this. I let it warm up for 3-5 min and it runs beautifully.

[GrandRapids750K3]

Same here... I have to adjust the idle screw every start... 3-5 minutes on the choke and throttle and usually stopping again at the corner to turn it down a bit more and she's ready to fly... All my friends don't get it... But I guess that's why their bikes have no character...

[Duke McDukiedook]

Adjust the idle screw only after the bike has sufficiently warmed up, then you won't have to fiddle with it at a later time.
Goosing the throttle a little until warmup is attained is something that is a part of owning these wonderful machines.

If you don't like it just buy a more modern bike.

[EricHa]

The CB550K that I bought has the same cold start issue as Jacob's. It's like the choke doesn't work, but I'm pretty sure that it is functioning correctly. Most old fours will idle up with the choke on, but this one doesn't seem to do that. It takes a steady hand and throttle fiddling to get her to start. So this is just the way that the SOHC fours start up?

[Duke McDukiedook]

I have to goose a little with choke fully on then take the choke off once it is running then goose at idle until it warms up.
If I keep full choke on for longer than startup it will die.

Nature of the beast.


 

[lucky]

We cannot help you unless you give us ALL the proper information.

1977.

DOES THE CHOKE WORK??? Yes or NO?
Do you have the 1977 carbs with the accelerator pump?
Does it work, and do the spray jets function?

If you have pods and a 4 into 1 exhaust you will need a larger idle jet.
Or it will be hard to start even WITH the choke.
I would bet that with a squirt of starter fluid it would start.

[TwoTired]

This is pretty sketchy information.  And, not enough detail for an accurate diagnosis.  I'll put comments in Blue.

77 550k, takes full choke and playing with the throttle to get it to start, then sputters and will die unless you keep giving it throttle.

The throttle has a coupling to choke on this model if stock (not mentioned).  It might need adjusting the choke idle speed screw.
Full choke on cold start up is routine.  And, it matters if it has the stock air filter and exhaust. So, tell us these details.

I set the timing, carbs rebuilt,
there is a very wide variance of definition about "rebuilt", including by who and what was done during.
new spark plug etc.
The number on the spark plug matters.  NGK D8EA is a colder plug and makes cold operation rather nasty for the CB550.  You should have D7EA heat range.
 it does burn oil on start up, so maybe  are slightly oil fouled on startup but clear themselves after running?

I suspect it has the same thing wrong with it my 78 does, bad valve guide seals (and possibly bad valve guides).
Have you seen any evidence of oil burning on the spark plug tips?
What is the mileage on the motor?

[EricHa]

I have to goose a little with choke fully on then take the choke off once it is running then goose at idle until it warms up.
If I keep full choke on for longer than startup it will die.

Nature of the beast.

Thanks for the info. I like the little beast. She's a keeper. 

[Jacob]

Wow thanks for the replies, this is a very passionate site.

It is the pd46a carbs, so to answer the accelerator pump question....I don't know.
Carbs were rebuilt by me...a noob. I took my time and followed a guide I found on this site but I can't promise everything is prefect.

Choke does work, if it didn't it wouldn't run. I do have an appointment with a shop to get it tuned, just trying to learn everything myself.

Mileage on the odo is 23k, but the bike was pretty haggard when I bought it so who  if this is accurate.

Anything else I missed? I'll gladly give as much info as I can for your help. I'm learning

[TwoTired]

The CB550 never had an accelerator pump as stock equipment.
The PD carbs on the CB750 and CB650 do, though.

[Jacob]

Also, no pods, it has stock exhaust. And new D7EA Plugs.

It is a K model but has the 4 into 1 exhaust from the F model.

There is a little oil on the plugs, I bought this as a project bike and just want it to run through the summer. I have an engine rebuild planned for this winter.

[TwoTired]

With the exhaust change, the stock pilot screw book setting is not to be relied on.  As a guess, I expect it would need a richer setting, which would help when engine is cold.  Still, the choke plates must reach full closure, and the idle speed to choke coupling adjusted for run speed, which will vary with the amount of choke selected.  This is a separate adjustment from the main idle knob which only dominates when the choke is fully off.

I'm surprised the 4 into 1 doesn't have interference problems with the brake arm and kick start lever.

[Jacob]

I'll try to richen it up slightly.

This idle speed to choke coupling thing you're talking about. Can you explain more, or it's there somewhere to read about it or do I just need to go look at it?

The 4 to 1 did interfere with the brake....until I bent the pedal out a bit. I feel like I would win the "how bad did t the PO screw up your bike" thread

[TwoTired]

This idle speed to choke coupling thing you're talking about. Can you explain more, or it's there somewhere to read about it or do I just need to go look at it?

See The Cb550 Honda Shop manual chapter 19.  There is a fast idle adjust procedure (pg179 in my edition).

[Jacob]

TwoTired, while I have your attention and expertise I have another question.
 I went to adjust my clutch by loosening the locknut and turning the screw. But it stops turning before all the slack comes out of my cable. I can take enough slack out at the handlebar but I have to turn that adjustment coMpletely out.

Is my clutch worn out beyond proper adjustment? Did my question even make sense? I searched but didn't come up with anything.

[750K]

Ive always found my 77 cb750 took awhile to warm up, but it always started easily. That was till after I had a local Honda shop rebuild my motor and carbs over the winter, while the motor work has been great the tuning just didn't seem right. I checked and adjusted my valves and points, that helped a bit on the hard start a bit. I then checked and adjusted the sync of the carbs and adjusted the mixture a touch, it fires up imeadiatly and warms up quicker than it has since I've owned it. Get the 3000mile tune up in order and I'll bet you find things are under control, or at least way better. In my dept the cold start and hard start were all carb tuning for the most, runs like a new bike now.

[TwoTired]

TwoTired, while I have your attention and expertise I have another question.
 I went to adjust my clutch by loosening the locknut and turning the screw. But it stops turning before all the slack comes out of my cable. I can take enough slack out at the handlebar but I have to turn that adjustment coMpletely out.

Is my clutch worn out beyond proper adjustment? Did my question even make sense? I searched but didn't come up with anything.

Do you have the Honda shop manual and study chapter 10?
The clutch cover adjustment is described in the owners manual and should be done before the cable adjustment, just to get the actuating lever in range of the cable length.  It also positions an over-center cam in the correct alignment so that the lever can be more easily moved as the springs in the clutch compress and get stiffer.

The cable adjusters ensure the clutch springs are allowed to apply full pressure to the plate stack when lever released, and position the actuation range to enable full disengagement.

If the clutch is worn, it will slip under power and load.  I've not seen one need replacement due to adjustment range issues.  On cars yes, but not on the SOHC4.

Cheers,

[phil71]

There's no point in dancing around this.. I don't care what model, year, engine size or color.. you've got carb issues.
If compression is even remotely in the ballpark, and the fuel tap flows like it should, it only means you've missed something in the carb cleaing.
Disassemble it to the last jet and screw, clean 'em 3 times.. (and I mean every single opening and circuit), and your problems will go away. They are a far more precise component that most people give them credit for, and as such, are more finicky than you would like to believe.
   (this coming from a guy who has missed plenty of things while rebuilding carbs).

[orange550]

I had my carbs out 3 times trying to get 'em working better, then realized I kept missing the cleaning of the emulsion tubes. No matter what you do, they will never get clean if already sludged up. I pulled them out, and they were plugged something terrible.

Also, my 74 550 fires up instantly when cold, but runs like crap for 5 or more minutes. I used to crank in the master idle, but then I'd end up having to crank it back out later. So now I just leave it set at optimal for when warm, and use the throttle to keep the bike running until warm. The joy of old bikes I guess.

[Duke McDukiedook]

Keep them on the rack when you clean them though, no need to derack them for a cleaning.

[AbbyRider]

My PO had a throttle lock on the bike. I always thought it was because he liked to cruise the long highways of this great country. I now suspect he just used it for startup.

[orange550]

Keep them on the rack when you clean them though, no need to derack them for a cleaning.

How do you get the emulsion tubes out if you leave the carbs installed? I thought about using something thin with a very slight hook on the end, but I was afraid I would score the top of the emulsion tube where the needle comes down thru.