Motorcycle Repair: CM450e Carb problem, rust problem, float bowl

Question
I have done a bit of work on the 1983 and it was running good for the summer but started back firing in right muffler and having hesitation problems.  Tank was rusting and i pulled and cleaned the carbs and added an inline filter but noticed that rust particles still getting to the float bowl.  I have already pulled and cleaned the carbs twice this summer but its starting to run rough. At its worst it has had difficulty starting and when pulling off whould stall unless i added choke.  Recently found carbs at local boneyard off of an 82 CM450E however once i cleaned and swap them, the idle speed was extremely high (idle speed screw had no effect.  turns out the 82 has differs by having both primary and secondary plus slow jets.  in the process i check plugs which seemed about right with a slight tanning on one point of the insulation. Where can i go from here?  Can the 82 Keihin carb be adjust, rejet or plug.  can the pilot screw (set to 2 1/4 turns out like spec) be tightened. If the back firing continued after second cleaning and swopping coil could the problem exist in valves or vaccum? Lastly standard, X, O-ring replacement chain?

Answer
I can't tell you the differences between the 82 and 83 models but in that time period there were a lot of changes driven by emissions so it's possible there's enough differences that the swap might not work.  However the jets don't control the idle speed so I'm betting you have a throttle cable adjustment problem.  The pull cable needs to be adjusted so there's about 1/8 of an inch freeplay in the throttle. If you crank the handle bars from one side to the other and the idle speed changes, you have a cable routing or adjustment problem.

You have to address the tank rust problem which is the root cause of your problems.  The carb swap may help for a little while but the new carbs will plug up too. If the tank wasn't plugging the carbs, the original carbs would probably still work after a good cleaning.

I, personally, prefer the o-ring chains because they are less temperamental about oiling.  If you forget to oil them every day they won't wear out as fast.  

Regards
Rich