I've been working on getting the orange GP 150 back to running shape. (See Part 1, and Part 2). I previously replaced the stuck clutch, only to discover that the top end was locked up solid. It is time to investigate further. First, I took off all the extraneous body parts as well as the carb and exhaust. I removed the rear shock, so I could get the motor to pivot lower to allow me easier access to the top end.
Click below the jump for more exciting motor repair action!
I got all of the motor tin off, and then pulled the cylinder head nuts. The cylinder head popped off easily. I didn't see anything obviously wrong at the piston crown, so that is good. But still, it was locked solid.
Here is a view up at the bottom of the piston. Noting exciting here. No score marks, it all looks fine, more or less.
Here is the top of the piston. Note the goop, and what appears to be moisture at the bottom. That is bad. How did it get in here? I tugged on the cylinder, and it moved easily. Well, that is a pleasant surprise. I expected the piston to be totally rusted in the bore. Nope. So I pulled off the studs, and got the cylinder off.
Here is the inside of the cylinder. Water. Not good. The bore looks ok. I'll test out the spec, but it looks like I might get away with a hone and some new rings.
Now this is where it gets ugly. The piston would not move because the crankshaft is rusted. The big end bearing is completely locked up. Suck.
From this angle it doesn't look so bad, but trust me, this crank is toast.
I did all this work weeks ago. Since then, I've been spraying the big end with penetrating oil on a daily basis. It is still stuck. I'm hoping to get some time to really tear into this motor again this weekend. My plan is to hit it with some serious heat and a little "persuasion" and see if I can get the crank to turn. I need to get it to move so I can get it out of the crank case. It is stuck in such a way that it just won't clear.
Stay tuned for the next installment in the GP 150 saga!