CB 550 overheating, some weird timing issues too... with some bike pics!

N

nestcraft

New Member
I have a 1978 CB 550 that I have been working on over the last few months, basically got it for free and am converting it to a cafe. (pictures attached) I have put almost 1,000 miles on it over the last 1.5 months and it has ran pretty good, the last few weeks I have been dialing in the carb jetting. She ran a bit warm but not so much that it ever overheated. I rode many times for 2 -3 hours with no issues.

About a week ago I changed the oil, I was running Honda Brand 10w40 and I switched to Bel Ray EXL Mineral 20w50 and added Rislone Zinc additive as recommended by several on this forum. I also replaced all of leaking O rings in the oil pump, replaced the shifter shaft seal, counter sprocket seal, brake lever seal and changed the clutch plates.

I also realized I had a massive vacuum leak at the intake manifold so I replaced those O rings, while the carbs were off I decided to "fine tooth comb" everthing internal and found out that I had overlooked some build up inside the idle jets.

Seems like this should all be good right? Well, it has been downhill ever since!

Right now my set up is this: (bike has about 18,000 miles on it)

#40 Idle Jets (OEM ,although one of these four seem to have a slightly smaller hole than the others....)
#105 Mains
Uni "short" foam pod filters- oiled
Mac 4 into 1 Exhaust
NGK D8EA plugs
Stock points and condensers
Stock coils

My plugs are telling me that things are running rich, I have not done a formal plug chop yet and won't be able to until I get the overheating figured out. What is driving me crazy is that I fixed some major air leaks and cleaned a bunch of gunk out of the idle jets so this thing should be running much richer right?!!! No, now it is overheating... within 10 minutes of riding.

I have set the valves and rechecked the valves. I also ran it a bit with the tappet covers off to verify that oil is getting moved through the top end. It is!

I have synched the carbs everytime after any jetting changes or fiddling. It idles great when cold, and runs great until it gets too hot, then it detunes itself.

I checked the timing the other night and it was advanced a good deal... hmmm. I got it set dead on, checked the points gap, dead on. I ran the bike for a bit... rechecked the timing, 1/4 was off again.... hmmm. It must have been something I did, do I reset it again. Ran the bike for a bike, checked the timing and it seemed OK. Today I took it out for a spin and it got hot enough to detune itself again after about 10 minutes of not very aggressive riding. I put it on the lift and checked the timing.... it was off again, slightly advanced. So I set it.... dead on. Ran the bike for a bit and the timing was off again. I pulled the plate off and checked that the springs and everything were in good shape behind the plate and they were.

I don't have a timing light so I have been setting the timing with the static method.

WHAT THE HELL IS GOING ON!!!!!!!!!!

Can the timing make a bike run that hot?
If the timing is advanced will the bike run strong?
Can my jetting be that lean even after the air leaks have been fixed and if my plugs are black and sooty?


I am at my end of what to do next, someone please lend me a few next steps.

I love reading this forum but now I guess I AM THAT guy with the crazy, possessed bike.

Thanks in advance. If you need other info please just let me know!
Mike
 

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buy a chinese timing lite.

check and monitor cam timing.

pull stator to see if the key has sheared . . if yhe f;ywhee; is slippimg on the crank, your timing will appear to change even though it isnt.

dont try to jet bike until timing is fixed because timing affects jetting

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This might sound stupid to the oil experts but why not change back to the oil you were using when it didnt overheat, and see what happens. You are having a cooling issue, not a jetting issue.

Iff the bike ran great before, stop messing with the jetting! If it idles fine and doent chug when applyi g throttle, stop messing with the sync! Jetting requirements do not suddenly change unless significant engine damage is beginning to occur. These things are only going to make you pull your hair out for no reason.

There is no reason to add zinc to an engine that has been broken in.
 
Although I don't use it, ZDDP/ZDTP are recommended. Vintage oil had these additives in greater quantity than modern engines and given the propensity of these engines (Honda twins, especially) to take a while to get the oil up into the valve train, ZDDP will help alleviate wear on the cam and followers.
 
Recommended by some, not all. And the oil war rages on.

You switched oils, switch weights, and added something it was fine without, and it started overheating. Oil is a major part of your cooling system. I'm not magically solving this issue and neither will anyone else, but would be ignorant to pass over these facts.
 
Yeah, I would switch back to the original oil you were using. If the bike is running slightly rich after re cleaning the carbs (makes sense if they were a bit dirty could have less fuel going places and have it tuned before but now its rich) then the overheating thing could definitely be from timing. If you feel like forking out a few more bucks, you could always slap an EI in...what clip are your needles on?
 
Did you ever get to the bottom of this problem hope it was as simple as the oil
 
Always and forever is one of my top 5 favorite albums of all time. There are more than 5 top fives, but they all belong there.
 
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