Motorcycle Repair: Running between 5000 and 6000 rpm, exhaust leaks, throttle cables

Question
Hi I have recently had the carbs cleaned and the timing set on my cb250 k4 but now I notice that it pulls fine up to 5000 rpm and then pulls reasonably well from 6000 rpm well up to red line. However, between 5000 rpm and 6000 rpm is a struggle. It will pull through eventually but takes its time. Pulling the right hand plug lead off the bike seems to rev throughout the range but if I replace it and pull the left hand lead off I get the symptoms above. Do you have any idea why the right hand cylinder should show these symptoms just in that rev range. The only other thing that I've noticed is that the right hand cylinder does seem to run leaner.  Many thanks

Answer
Dex, the 250-350 carburetors need some careful care and correct parts to run properly.

http://www.cmsnl.com/honda-cb250k4-england_model8207/partslist/E19.html for a list of parts.

Poor running on one side could be a lot of things.....

Low compression... adjust valves and check for even compression on both sides.
Ignition point set contact faces dirty/worn
Weak Condenser
Spark plug cap with excessive resistance.. should be 5k ohms
Damaged coil secondary lead. They break off near the coil body
Bad coil primary windings.. should be 4.5 ohms on small primary wires.
Loose connections at coils for power/condenser leads.
Carburetor calibration incorrect for application
Carburetor diaphragm slide hardened or has a pinhole/tear in it.
Carburetor throttle cables are not synchronized
Air leak at intake manifold/cylinder head face.
Torn intake manifold rubber. I had one the other day on a CB350. Check the recess where carburetor spigot fits in.
Exhaust leaks between cylinder head port and end of exhaust pipe.

Bill Silver