Topic: CB550 Post top end rebuild... now runs badly and no power

[farr2gonn]

I did a top end rebuild on my motor over the winter and went to start it yesterday. I started but ran bad. It has no power and is sputtering. I took it for a short ride and by the time I got home the number three cylinder wasn't firing. Before I did the rebuild, the motor ran fine. I only did it to stop and oil leak, I know this isn't the greatest option, but what's done is done. While I was in the motor I replaced the piston rings, Tore the head apart and did the valve seats, new valve seals, and put all new gaskets. I am worried I may have not set the cam correctly when I put it in, but there is no binding. I thought it may be a really bad carb sync but there is only 5psi vacuum that shows on the dial. I recently tore the carbs apart and cleaned them including the other emulsion tube. Any help would be greatly appreciated!
1976 cb550k
Dyna coil 5ohm
Pod filters
Carpy exhaust
110 mains/ 38 slows/ clip 4th from top
Properly set the valve tappets
Set point gap, but when turning the points there are sparks coming from them..Is this normal?


If any other info is needed just let me know

[BigHoss]

Sparking points are the result of bad condensers. Perhaps this is, or is at least contributing to, your problem.

[TwoTired]

Do a compression check.  With that low a vacuum I'd worry about bent valves from improper cylinder cover installation.

Did you heed the manual's warning?

Did you follow the Honda shop manual cam install alignment instructions?

[TwoTired]

Sparking points is a normal occurrence and can't be prevented.

Excessively sparking is another matter.

[farr2gonn]

When I installed the valve cover I backed out the tappets all the way and used rubber bands to hold them back. They look to be aligned right. A compression check will be dine soon, I just can't find the right attachment that fits the spark plug hole. 

[drjeffreys]

pull the cam cover, rotate to tdc 1-4 and ensure the cam notch is facing sideways. No point doing anything else if you're unsure if you clocked it correctly.

[farr2gonn]

I pulled the can cover and the can was set in the right direction. What I found was the number three exhaust tappet came loose. I retorqued the head and put the cover back on. It took one kick to start and it is finally running smooth. Now its time to reject the carb and sync the carbs. It had to be something simple.

[iron_worker]

Did you happen to add pods during your "rebuild"? If you did and it now it runs poorly it's because your carbs are now way out of tune. The change in inlet restriction completely changes the jetting requirements of those carbs.

IW

[Duanob]

First off welcome to the board farr2gonn. There are a few PNWers on here.

The 550s are pretty simple and it is usually a simple fix unless people start modding them too much. Sound slike you fixed your problem with the #3? Give us an update.

[farr2gonn]

I've put about 200 miles on it since the rebuild, and the bike is running great. I tried several different combinations on the carbs to get it tuned just right.

1st setting
-105 main jet
-38 slow jets
-Raised the needle one notch
-Air screw 1.5 turns

With this it had decent low end, but no top end. The exhaust would pop like hell every time I let off the throttle. I also had no power 1/8 throttle from a start, and a flat spot at 4k rpm. I synced the carb and it did help a little bit on taking out the flat spot.

2nd setting
-110 main
-38 slow
-stock needle position
-1.6 Air screw

Great top, but no low end. The popping went away! Still a little sluggish from a stop at 1/8, and the flat spot went away. I of course synced the carbs again.

I do have a question though. After riding it in this configuration for about 150 miles now I feel the old symptoms coming back as in the flat spot and the 1/8 throttle is really sluggish now. Could it be due to the piston rings seating?
When I get the chance I am going to drop the needle down one and see how she feels. I am just waiting on a new chain to take her out again.

Thanks to this site I actually was able to get through my first top end rebuild on any motor!