Episode 19: Top End Rebuilds Part 1
Episode 19 is part 1 in our series about rebuilding the top end of your motor. This episode will cover disassembly of your top end, and goes over the important components of the motor top end as well. Make sure to listen to Part 1 before moving onto the new Episode 20, part 2 of Top End Rebuilds. Check out the notes below for the important points to follow.
Episode 19 Outline/Notes:
What is a Top End?
The top end of a motor is anything from the cylinders and up
Why?
To replace worn or damaged parts
Performance upgrades
Burning oil
She's just tired
Engine in or out?
Not all bikes require you to remove the motor from the bike
May be easier to rebuild it on a workbench
Where to start?
Remove gas tank
Remove air intake and carburetors
Remove exhaust
Remove cables (clutch cable, tach cable)
Drain fluids (oil, coolant)
Disconnect battery
Remove spark plugs and wires
If it's connected to the motor, disconnect or remove it
Removing the head:
Check manual for proper process to relieve pressure off of valve train
Remove cam(s), rockers, or cam followers
Remove head bolts/nuts
Remove heads
Removing valve springs and valves:
With the appropriate valve spring compressor, compress valve spring
When valve collars are exposed, remove them with needle nose pliers or a magnet
Make a char to organize valves
Removing cylinders/jugs/barrels:
Slide cylinder off piston
If motor is removed from the frame do this while the motor is tipped forward
Cover case opening with towels/rags
Removing pistons:
Remove wrist pin clip from one side
Slide wrist pin out
Remove piston from connecting rod
What to look for:
Pistons:
Clean thoroughly and inspect for excess wear, cracks, or any damage
Measure the diameter of the piston on the skirt 90 degrees from the wrist pin guides
Refer to manual for proper piston to cylinder measurement
Replace if needed
Valve Train:
Inspect valves for damage (cracks, bent or excess pitting)
Measure valve spring tension
Check cam lobes and guides for scoring or heat damage
Check that valves move freely in valve guides
Cylinders/jugs/barrels:
Check for scoring/scratches, grooves, or corrosion
May need a re-bore
Heads:
Check for warpage or corrosion
Check guide surfaces
Inspect valve guide seats