CB77 doesn't run well, bad compression?

[conbs]

Has anyone ever tried the 50/50 ATF/Acetone mix for loosening stuck rings?

[canadianCL77]

I have the exact same issue. 120 and 60. Cadman, thanks, you helped me earlier. I wish I had read this a few hours ago. On my neighbours advice I put oil in the cylinder, when I had a jug of Mystery Oil sitting right next to the oil. It brought the compression up to 100, I only let it sit for a few minutes. What next? Should I still try Mystery Oil? How bad do you think this is? Should I still try adjust the valves, I am assuming that it is worse than just that? The bike is new to me, so no history.

Any advice is greatly appreciated,

Nathan

[cadman]

The oil in the cylinder was good for a test but probably won't help "unstick" the rings if that is the problem. There are lots of things available to inhibit rust. I usually use PB which is normally used to free stuck nuts or bolts. If you can't find it I am sure there are others. (Note WD40 won't do it)

Remove the plugs and crank the engine to remove as much oil as possible. Put an ounce or two of whatever you can find in each cylinder. Wait a day or two and add more. Sometimes I do this 3 or 4 times. Somewhere along the line do another compression test to see where you are at. Make sure the valves are closed and the throttle is wide open when testing.

After a few tries clear the cylinders, replace the spark plugs and try to get it started. Run it for a bit and recheck compression.

[jleewebb]

[/quote] Should I still try adjust the valves, I am assuming that it is worse than just that? The bike is new to me, so no history. Any advice is greatly appreciated, Nathan[/quote]

A too-tight exhaust or intake valve can cause low compression...been there...

my advice for what it's worth would be to go ahead and check the valve clearances before you do anything else, especially since bike is new to you,...not that hard...

[canadianCL77]

Yup, it was the valves. Three of the four were too tight. Compression is now 150/150. Just doing an oil change, then on to tuneup and checking out drivetrain. Hopefully will have it roadworthy before the end of the summer.

Thanks for the advice.

Also, my rear sprocket is "hooked". Should this be replaced before it is ridden? The odometer only reads 3100 miles, could the sprocket wear that quickly, or is it likely the odometer isn't accurate?

[jleewebb]

Yup, it was the valves. Three of the four were too tight. Compression is now 150/150. quote]

Makes me feel good to get one right, thanks for replying... Probably checking valves first should be part of any compression test procedure.

In my case, trying to figure out why bike was so hard to start, I removed the spark plugs one at a time to check for spark. Replaced first plug before removing second. It got good spark on each side when I turned it over, but I noticed the starter was spinning the motor considerably faster with one plug out than the other ie, lower compression on side with plug installed. That led me to a tight exhaust valve I'd just checked 500 miles ago. After adjusting I went to turn the engine over with the starter to recheck, and VROOM. Good thing I'd taken the vice grips off the flywheel nut.

This was after cleaning carb jets, resetting float level, and replacing plugs and points and re-timing, of course, but I told myself all those things needed to be done anyway...

[jensey]

Also, my rear sprocket is "hooked". Should this be replaced before it is ridden? The odometer only reads 3100 miles, could the sprocket wear that quickly, or is it likely the odometer isn't accurate?

Does it matter how the sprocket weared out in relation to the question "replace or not" ?

The question if the bike really did 3100 miles or not doesn't influense the state of the sprocket, isn't it ? The answer to the question of the bike did 3100 or more miles is more likely to be found in the brake hubs, or in the engine, ignition points, etc.

But, yes, replace if something is weared out, no question about it.

And yes, a sprocket can wear out very quickly, especially when not lubricated at all and driving in winter or in the wet or and sand.