Motorcycle Repair: Honda CM450E loss of power in 5-6 gear, honda cm450e, vacuum leak

Question
Hi Chris
I bought a Honda cm450e for my wife about a year ago and it runs great but there is a power loss in the higher gears and it will carbon file plug #2 right side at about 80 miles of travle.There is a little black that come out the left pipe some times as she shifts.Do you have a clue on what I need to look for to fix this problem or where to start?
Thanks
Ken  

Answer
Hi Ken.

You have a really old machine there.  Because of that and based on what you are describing, I would check the following;

1) Manifolds - good seal to the head and to the carbs.  Check for leaks in the manifolds themselves.  A vacuum leak could cause problems like you have described.  Visual check will only tell if there are major cracks in the manifolds.  Use prescribed testing methods to find "invisible" leaks.

2) Carbs - clean and make sure that the mixture hasn't been changed.  If mixture has been changed, then you may want to get it into a shop, unless you know how to properly adjust mixture.  Also make sure that the needle valves haven't come loose.

3) Valve timing - not the most likely issue, but worth checking if all else is good.

Good luck and ride safe.
FALCON