Motorcycle Repair: hi speed hesitation, honda shadow spirit, cylinder head gasket

Question
Hi, I have an 05 Honda Shadow Spirit with 1230 km on it.Bought it new from a dealer 13 hours away. Last week when I took it to 100km/hr it hesitates and refuses to go any faster.I drained the carbs several times to see if there was any water. The plugs are a nice tan colour. I added gas line antifreeze to dry up any moisture in the tank. I still have the problem. It starts good and acellerates well in the lower gears but in 5th gear at 100km/hr it hesistates. Thanks for your help.

Answer
Hi Tony,

Check for air intake restrictions. Check the following...

Poor Running or No Power at High Speed:

Firing incorrect:

Spark plug dirty, broken, or maladjusted
Spark plug cap shorted or not in good contact
Spark plug incorrect
IC ignitor trouble
Pickup coil trouble
Ignition coil trouble

Fuel/air mixture incorrect:

Starter plunger stuck open
Main jet clogged or wrong size
Jet needle or needle jet worn
Air jet clogged
Fuel level in carburetor float chamber too high or too low
Bleed holes of air bleed pipe or needle jet clogged
Air cleaner clogged, poorly sealed, or missing
Surge tank duct poorly sealed
Water or foreign matter in fuel
Carburetor holder loose
Fuel tank air vent obstructed
Fuel tap clogged
Fuel line clogged

Compression low:

Spark plug loose
Cylinder head not sufficiently tightened down
Cylinder, piston worn
Piston ring bad (worn, weak, broken, or sticking)
Piston ring/land clearance excessive
Cylinder head gasket damaged
Cylinder head warped
Engine not sufficiently warmed up after lash adjuster installation
Valve spring broken or weak
Valve not seating properly (valve bent, worn, or carbon accumulation on the seating surface)
Hydraulic lash adjuster damaged (worn, seizure, or spring broken)
Hydraulic lash adjuster oil passage clogged

Knocking:

Carbon built up in combustion chamber
Fuel poor quality or incorrect
Spark plug incorrect
Coasting enricher trouble

Miscellaneous:

Throttle valve won't fully open
Carburetor vacuum piston doesn't slide smoothly
Brake Dragging
Clutch slipping
Overheating
Engine oil level too high
Engine oil viscosity too high
Drive train trouble
Final gear case oil viscosity too high
Air suction valve trouble
Vacuum switch valve trouble
Balancer mechanism malfunctioning


Respectfully,
Mark Shively