KH500 Refurbishment: Engine (part 1)

This is Part 1 of the KH500 engine story.  I can already tell this will need to be split into multiple posts, due to the damage I found this past week :(

I am still hopeful that I won't have to go into the bottom of the engine.  It remains to be seen if that will be necessary.

Below, the right cylinder has been removed.  The studs were nasty with rust (since cleaned up)

Center cylinder off

All cylinders off, pistons have the typical two-stroke oil deposits

Oil drained into the left section of the crankcase via the oil injection system.  This would certainly hydro-lock the left combustion chamber and damage the engine if not drained out.  It isn't a four-stroke, so oil doesn't belong in the bottom of the engine.

Pistons removed.

OUCH!!  Center piston is gouged.  So is the cylinder, at the transfer port.  A circlip holds the piston wrist pin in place.  The circlip came off and probably did this damage.

Scored middle cylinder at the transfer port.  Not sure if there is enough cylinder sleeve remaining to machine this out :-(  It's already bored 0.040 over.  I think you can only go to 0.080

The circular clips shown below are what I think did the damage seen above...

On the bright side, I cleaned up the cylinders and straighened out several bent cooling fins.  This is a before view of the exhaust side of the right cylinder.  Don't like the black paint-it's not original.  The cylinder head at right is how the engine should look.

Below, bent fins - since straightened out.  I tried using paint stripper to remove the black paint, but it wasn't possible to remove paint deep between the cooling fins.  I'm going to need a bead blaster.  But before I do that, I need to talk to a machine shop to see if the damage on the center cylinder can be machined out.  Notice I polished carburetor inlet at the left!

I ordered a bunch of parts before finding the engine damage.  If it weren't for that damage, I would be on budget.  Kinda wish I had waited on the other parts now...  It's probably going to be a while before I can get the engine completely back together.  I can at least replace the side covers when my gasket kit arrives.

On the other hand, I've always wanted to have race-ported pistons and cylinders.  Since I will have to send these out to have machine work done, maybe I will get Stage II porting done at the same time...