77 CB 550K Running on 2 Cylinders

B

bhorst

New Member
I have been a long time lurker here, but never signed up to post until I inherited a 77 CB550K that was essentially a barn find at my in-laws.

It wouldn't start, so I took out the plugs, kicked it over a few times to make sure there was nothing in the cylinders and exhaust and then cleaned the carbs and put new seals back in the bowls and cleaned everything at our local bike shop.

I have compression in each cylinder, 100 lbs or so. and each spark plug has spark when I ground it and crank it over.

I can drain the float bowls and know that each carb appears to have gas in it.

I can get it to run with full choke on, but only fires on 2 cylinders. I believe it fires on 2 and 4 (staring from top down left of the engine).

The rubber carb boots are in pretty good shape but they are original, and I am wondering about vacuum leak? I have not tried swapping plug wires around to see if they fire the other cylinders since I didn't want to mess anything up.

Any other reason it wouldn't fire? Or any other paths to eliminate some problems? Any suggestions?

Thanks!
 
If you have spark and compression I would say that leads us to fuel. Since there is indeed fuel in the bowls, that might lead me to believe this is a carb related issue. Possible causes: plugged pilot jets, carbs are not synched properly, mixture screws are out of whack, vacuum leak.

It would be beneficial in any case to go through the full tuneup procedure and check your timing, valve clearance, carb synch, etc.

If the bike is in rideable condition, you might take it down the block and see if it starts firing the non-op cylinders once you get on the main jets. That would indicate to me that the pilots are plugged up and need to be cleaned a bit more thoroughly.
 
everything coyote has said. spend a good bit of time cleaning the carbs and blowing them out with compressed air. if spraying some carb cleaner or starting fluid into the carb of the cylinders not running jumps them to life, you've got dirty carbs to sort.
 
Thanks for the help!

I will have to pull them off one more time. The carbs have PD and then 46AAOJ1 stamped on the sides.

Haven't found tons about them, or heard great things about them.

I have had them apart one time to clean in an ultrasonic cleaner and we did blow air back through them as well. I didn't even use my gas tank once they were back on. I just fed it out of a new aux tank just in case.

Currently if I have it running on the 2 cylinders and tweak the throttle at all it just bogs down and wants to die. If I use some magic I can make it rev up a little (4000), but that's hard to get it there.

I do have the shop manual, so will have to run through the steps and see where we are. I'm not a full fledged mechanic so there are some things that are beyond me. Good thing the shop manual has lots of photos.

Anyway to temporarily seal carb boots while it's parked?
 
Get it running and spray WD40 around the boots. If those cylinders suddenly come alive, you've got a vacuum leak
 
I got the bike running on 2 cylinders again.

I soaked the carb boots with WD-40 until it was dripping off and didn't hear any difference at all. Dead cylinders didn't seem to kick on.

Still running with choke only wide open. Cylinders 2 and 3 are cold still.

I randomly decided to shoot starting fluid into the carb while it was running and the engine revved up when I did that. Cylinder 2 revved up a lot and 3 revved up a little less although I could have not shot as much in there. The pipes on 2 & 3 were warm to the touch when I did that as well. I didn't want to keep going for fear of setting something on fire.

I would assume I need to pull the carbs again and reclean and reblow air. I am thinking there is something in there that is leaking or clogged right?
 
bhorst said:
I am thinking there is something in there that is leaking or clogged right?
Click to expand...

Probably correct.

Just FYI for future reference, your bike has two ignition coils. One coil fires 1 and 4, the other fires 2 and 3. A lot of times if there is a case of two cylinders not firing, that could indicate an ignition issue, one set either being way out of time, or a dead coil. This does not sound like the case in this situation since you do indeed have spark (though if the spark is weak it may not be enough to fire), just something to be aware of. I would still check that your timing is spot on to rule that out, it's super easy to do. If you switch plug leads from 1 and 4 to 2 and 3 and vise versa, you can check to see if your problem switches cylinders. That would indicate a dead coil.
 
Thanks for all the help!

I took the carbs back off and started to take them apart. I also tried swapping plug wires, but that didn't fire the cylinders.

Not sure, but I think this may have had something to do with it.

olUewq4.jpg


One of the overflow tubes had a leak, so I had JB Welded it at the base. The other overflow tube was cracked at the base and a drop on the workbench took care of the rest of it, so I also JB welded it back in there.

It would appear that JB weld doesn't like gasoline after all or I did something wrong.

I am going to break them down again and run them through the ultrasonic cleaner.

Any better solutions to repairing the overflow tubes? Solder, gas tank repair kit, duct tape?
 
What kind of solder would you just recommend? I have done soldering of copper plumbing. Same sort of approach?

Do you just run a thin drill bit down the tube once they are soldered?
 
Thanks for all the help. I finally got it all back together and have it hitting all 4 cylinders. Did a deep clean again, new float needles and actually used FASweld to seal the overflow tubes. It is holding well. Found a guy in town with an extra set of bowls too so I am going to buy them and keep locked away. Thanks for all the help!

Sent from my KFFOWI using Tapatalk
 
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