Motorcycle Repair: yamaha wont start, spark plug wires, spark plug wire

Question
Thank you for your help.  I did a comprestion test and both cylinders were about 120.  Neither hold comprestion but i don't know if that is normal for a cycle or not.  After adjusting the valves it starts easier, but i still have no fire at idle on the right cylinder.  I also swaped the carbs back to the origial after cleaning them.  If i cover the right carbs air intake the cylinder starts to fire.  After thinking about that I took a shop rag and clamped it to cover the air intake.  Then had gas running out of tail pipe.  The parts bike I have for this is a '80 XS650G and am finding parts donot swap right.  So I am putting as much original stuff back on as I can.  If you have any other ideas I am happy to hear them.   Thanks again,
         Bill


Answer
Hi Bill.
 The fact that it is firing means that you have enough compression for it to fire, but the one cylinder not getting spark means that one side of the coil is not working.  Normally the entire coil goes as one unit, so I would start by doing a bench test on the coil as per the instructions in the repair manual.  If the spark plug wires are integral to the coils (not removable) and the spark plug wire is bad, then you will need to replace the coils.  Try replacing it with one off of the parts bike, but make sure the part numbers match first.

You will find many, if not most parts do not change over.  However, many will.

Hope that helps.
Good luck.
FALCON