Last kinks of my CB550. Trouble starting and problems with engine going out

[alexdecker]

Hey all

Alright, I have a few remaining issues with my CB550 F2 from 1977 that I wanted to run by you guys for advice. I have a feeling some of it might be related. I recently did the complete maintenance cycle (cam chain, tappet adjustment, timing, carb sync), and the bike seems to run great when warm. I am idling on around 1000RPM. But these are the things I am experiencing:

1. It still takes some effort to start up. Not a lot, but I’ve been led to believe that even when cold, these things can start up by one press of the start button. I would like my bike to get there. Right now it still needs some time and effort from the start motor, coupled with choker and small twists of the throttle. When it starts, I also have to give it a little throttle to get it to settle. Without that throttle, the engine usually dies again. Can it be a bad battery? Not enough spark? Bad coils? Bad wiring? Low compression? I am not using original Honda points. The ones I use can be a little hard to set so the firing matches up exactly. I usually have to turn the points to the outer limits of the plate and make the points gap as closed as possible (around 0.25-0.3 mm). I’ve heard that I don’t have to do this with original Honda points. Can that have something to do with the starting of the engine? I would love to get my bike to this point, where it just starts up: https://youtu.be/2k8U4bKgMjg?t=49

2. When driving on the highway and de-accelerating, sometimes the engine just go dead. Have to use the start button, and it starts immediately, but I find it weird that the engine gets killed like that sometimes. I thought the maintenance cycles helped it somewhat, but I still experience it now and then. What can the reasons for this be? Running too rich? I tried turning out the idle screw to 1 3/4 instead of the factory 1 1/2. The bike still runs fine, and haven’t experienced the engine going out since, but want to make sure it can’t be anything else either.

I wonder if these two issues can be related?

Some things to note about the bike: The spark plugs were a bit black when I took them out recently to check compression, which is another reason I turned out the idle screw a 1/4 turn more. The bike seems to run normal on this setting as well, although I seem to hear some more clunking sounds from the engine. Is there any reason for this, or am I just imagining things? The plugs are fairly new (3 years old and haven’t run that far) - should I buy new ones? Also, I measured the compression to around 25-30 on each cylinder, which makes me believe that my meter is broken. It had the same reading before I completely restored the engine, and I have no problems hitting around 180kmph on the highway. Also it idles fine and all that, so it seems unlikely that my compression is that low. But I don’t know what it actually is. Need to get a new meter.

I feel like if I can fix the start issues and not have the engine die when going 120kmph and de-accelerating, the bike runs almost perfectly (to my knowledge anyways), so really eager to fix these things, but fix them correctly so the bike won’t take any longterm damage.

What do you guys think?

[robvangulik]

Do you test compression with the throttle completely open?

[Trigger]

1000 RPM is too low, turn it up to 1150 . 25 to 30 PSI compression is too low, should be at it lowest 125 PSI. 175 PSI is good after a engine rebuild 

[Oddjob]

I'd check the connections and the contacts for the kill switch, does the electrics go out at the same time as the engine dies or is it just the engine dying that happens?

[alexdecker]

Do you test compression with the throttle completely open?

Nope. Am I supposed to? I test it cold. I take out one of the spark plugs, screw in the meter and with the kill switch on use the electric starter to get the engine to turn a few times.

[alexdecker]

I'd check the connections and the contacts for the kill switch, does the electrics go out at the same time as the engine dies or is it just the engine dying that happens?

I will test the control, but the switches are brand new. Also, the electrics does not go out. I can restart the engine while coasting just by pushing the Start button again (with the clutch held in obviously). But all lights are still on, to the best of my knowledge.

[Trigger]

Do you test compression with the throttle completely open?

Nope. Am I supposed to? I test it cold. I take out one of the spark plugs, screw in the meter and with the kill switch on use the electric starter to get the engine to turn a few times.

At 25 to 30PSI the bike should not even start. You are doing something wrong or the pressure tester is wrong 

[Oddjob]

I'd check the connections and the contacts for the kill switch, does the electrics go out at the same time as the engine dies or is it just the engine dying that happens?

I will test the control, but the switches are brand new. Also, the electrics does not go out. I can restart the engine while coasting just by pushing the Start button again (with the clutch held in obviously). But all lights are still on, to the best of my knowledge.

In that case the engine cutting out is most likely a bad connection on the kill switch or coils connection. Also, just in case, check the earth connection right by the coils on the frame.

[robvangulik]

Do you test compression with the throttle completely open?

Nope. Am I supposed to? I test it cold. I take out one of the spark plugs, screw in the meter and with the kill switch on use the electric starter to get the engine to turn a few times.

Yes, open the throttle completely, and let the engine turn over until the meter doesn't go up anymore. Now I'm curious what the meter will tell you....
And it works best with ALL the spark plugs out!