Topic: 74 CB200 No Compression

[CCypher]

Hiya guys, I recently picked up a project CB200T for next to nothing and have been attempting to get it running again. I've run into quite a snag however, after finally getting the right compression gauge for the job I've come to realize I'm only getting ~60PSI  or so in each cylinder, even after adjusting the valves.

My question to you guys is, are you aware of any other engines that would swap easily, or if there's anything common about these sorts of bikes that I might be able to fix easily and save the engine. I really don't want to have to part this out as it's only got 6600km or so on it.

Thanks!

[edit] After reading the post below mine, I think I may have administered the test wrong. I didn't know you should keep kicking until it tops out. Whoops. I suppose I'll post back if it still doesn't do well.

[Spanner 1]

Was the motor 'stuck' when you got it ?.....if so surface rust in the cylinder walls may have forced the piston rings into their grooves when the motor was turned-over and stuck rings = low compression.........

[Hush]

Sometimes (many times) it's user fault when the readings are low, with that mileage it better have a hole in each piston to read so badly.
I'm guessing it's a twin cylinder so try the old "thumb" over the spark plug hole instead, if it has enough pressure to blow your thumb out it has enough to run when gas and spark are added.

[patricke9]

Did you have the throttle wide open while testing?  Had the same issue, forgot when testing my CB550 & wound up with really low readings, did it over & compression jumped up t 145/cylinder.

[Bodain]

Why swap engines? You will never know the whole story until you disassemble it. I've picked up many bikes that had low compression. In some cases the rings are frozen in the grooves in the pistons. Sometimes you can remove those rings and clean everything up and reassemble. Now the rings can expand as they should and you have good compression.

Worst case, buy oversized pistons and rebore, that of course assumes it is the rings. You can know very easily if it's rings over valves... You have a compression reading of 60 PSI. Remove the plugs and drop a teaspoon of oil into each cylinder. Take a reading again. If the reading comes up dramatically, you have a ring problem. If it doesn't, you probably have a valve problem.

[Laminar]

Did you have the throttle wide open while testing?  Had the same issue, forgot when testing my CB550 & wound up with really low readings, did it over & compression jumped up t 145/cylinder.

Seconded.

[tbpmusic]

Take your time and do it right - they can end up like this if you do -
http://home.comcast.net/~tbpmusic/id55.htm

[Laminar]

And if you half-ass your way though everything, it looks like this:

[tbpmusic]

And if you half-ass your way though everything, it looks like this:

Mine was ten times worse than that when I started..........it was a disgusting, rusted out hulk, in that puke yellow they used to come in-ugh.....

[Laminar]

Here's what mine looked like:

[Bodain]

Well maybe it's just me. I like the BLACK rat bike, better than the red shiney one. Who's to say what's right as far as paint and looks go. I think most 70's bikes in stock form are downright UGLY...