Motorcycle Repair: 1980 honda cm400t carb, 1980 honda cm400t, necessary specs

Question
So are you thinking I got an electrical issue here?  I havent got a chance to dive into the bike yet, but the friend was pretty sure he had spark on the dead cylinder, but I know never assume nothing. If electrical, what are you thinking, coil?
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-----Question-----
I just purchased a bike from a friend. The bike completely misses on rght side; compression 105-110 both sides; he took carb apart and cleaned; spark on both sides; wondering what could be wrong here; maybe out of synch? I have never attempted carb synch, but was going to purchase a gauge set and manual and attempt;  What do you think and where would you start? thanks in advance jrw
-----Answer-----
Hi James.

 Sounds to me like you are on the right track.  Getting the manual is always the right first step.  It will have a troubleshooting section as well as all of the necessary specs for you to refer to.

Doing the carb synch is almost always very simple.  The manual will have instructions for it as well.  You will need to have the bike running to get the synch done right.

Check the plugs and see how they look.  You could have other issues that are not too obvious.  The manual will cover that as well.

Just remember that you need fuel, compression, and spark for the bike to fire right.  If one side is not firing, then the issue is electrical.  If it is firing, but not providing power, then the issue is either compression or fuel.

If it is firing, but not firing in synch, then the issue is either valve timing or ignition timing.

Good luck and ride safe.
FALCON

Answer
Hi James.

I gave you the likely possibilities.  You need to check each one out and determine what the real issue is.

To check if you have spark, remove the offending plug, reinstall it on the coil (just as if it were in the motor to run) and lay it against the engine so that it is grounded.  Try to start the bike and look to see if you have spark from the plug.  If no spark, then you have a bad coil.  Do this in a darkened area or at night.  That will give you the best view of the spark, if you get a spark.

 If you do have spark, then the issue is something else.

Good luck and ride safe.
FALCON