S
Simonator
Guest
The only damage I know of right now is the piston siezed in the cylinder. The crankshaft still wants to turn. I might take some pics when I disassemble it.
The only damage I know of right now is the piston siezed in the cylinder. The crankshaft still wants to turn. I might take some pics when I disassemble it.
S
Simonator
Guest
I just installed my new motor. She's a runner. Yay!
S
Simonator
Guest
how did you blow yours at 500 miles??
ZnsaneRyder
Member
- Local time
- 10:40 AM
- Joined
- Jun 19, 2008
- Messages
- 805
WTF?!? The piston is locked, but the crank still tries to turn? WOW you must have a LOT of play on your piston rod from bad wear!
What was the engine doing the last moments before it locked up? Maybe the engine is still salvageable or repairable. Do they sell new piston/rod replacements?
S
Simonator
Guest
The day the engine locked up it was lacking alot of power. that is the only warning sign I got. I did not notice any unusual sounds.
I just disassembled the engine. The crank is fine. Either the wrist pin roller bearing is completely shot, or the rod wore out. I am not sure which. There is EXCESS EXCESS play. It's ridiculous. That is obviously why it seized. I kept this engine very well oiled. I can salvage it. It requires a new cylider, piston, bearing (obviously), and possibly rod. I might rebuild it for something to do. The question is, is it worth it? If I buy parts from dax it will cost me: $50 for the cylinder, $20 for the piston, $11 for the rings, $10 for the bearing, and $9 for the head gasket. The rod isn't even offered. This brings the total to $100 SO FAR. I guess its not realy worth it. I can get a used engine for around $100 on egay
Last edited by a moderator:
arceeguy
Active Member
The rod is part of the crankshaft. The crank is two pieces that are pressed together, along with the rod, to form one assembly.
Maybe the top roller bearing let loose and the shrapnel got caught in the ports, locking up the engine.
S
Simonator
Guest
that would explain the excessive play...
I just took apart my other broken HT as well. I wanted to take a close look at the wrist pin and roller bearing assembly. These roller bearings aren't all they cracked up to be. I noticed the rollers in the bearing left some nice deep indentations on the wrist pin. Hmmm
I am not real familiar with small engines like alot of you guys are. This is all new to me. I have only worked on car engines. Here is what I don't understand. Why is there a roller bearing on the wrist pin anyway? Why isn't the wrist pin pressed into the rod and spun freely in the piston like car engines? is that just the way 2 strokes are because there is no oil pump?
S
Simonator
Guest
Another question. Is the roller bearing supposed to be pressed and or fit tightly in the rod? When i removed the piston it the bearing slid out with ease.
S
Simonator
Guest
yep, wrist pin roller bearing did let loose. That is why the engine seized. Another one bites the dust....
arceeguy
Active Member
Engines can use pressed in wrist pins (pressed into the piston, not the rod) or "free floating" wrist pins with keepers. The roller bearing is employed because of the scant lubrication available in a typical two stroke. It requires very little lubrication to function, and the open cage design allows more of the oil/fuel mist in the crankcase to contact the load bearing surfaces. The disadvantage is that the cage holding the rollers will break the moment you hit the "critical RPM" point, so they aren't tolerant to over-revving. In your case, with 3000 miles, maybe the bearing was substandard and failed, maybe it was weakened from a "high speed blast" down a hill and failed under "normal" use. Who knows?
Similar threads
