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(Reposted from Somethingawful.com forums)
Engine teardown time, and I found the problem.
OK. First thing you're going to notice is the amount of **** inside the cylinders. I'm pretty sure that was this engine's downfall. All that dirt and hair and **** was just laying inside there, eating away at everything. Although, the cylinder walls do look pretty good to me, and all the bearings seem tight EXCEPT..
#2 piston. (Facing forward, the cylinder on the left). The main bearing on the crankshaft is ****ED. How do I know this? Well, when lifting up and down on the piston, the con-rod/crankshaft journal has about 1/8" of play and makes an audible "pop" every time you do this. Now imagine that spinning at 7,000 RPM and... You get the idea. Basically, the crankshaft and conrod wanted to make sweet love to eachother, but everytime they got close, the main bearing kept cockblocking. "I've had enough of this" said the conrod, and with one mighty thrust it punched the bearing in the face, destroying it and thus securing the rod-on-shaft but****ery.
...I feel dirty.
...
...
Moving on, here's what I'm thinking happend to cause this:
Most likely a piece of dirt got inside the engine and clogged the oil passage for the main bearing, starving it of oil and blowing it up. Ever other part of the engine seems well lubricated and smooth (the camshaft caps even fissed out high pressure oil when I took them off). After blowing up, it got so much clearance that it lost oil pressure completely and that's why my oil light came on.
I have not split the cases yet and I'm not sure where to go from here. These are my options:
A) Scrap the entire bike and start anew.
B) Find a used engine somewhere (gonna be $200+)
C) Fix it. How do I fix this? I imagine the connecting rod and crankshaft are both fubar, so I would need to find a used crankshaft & conrod. Would a GS450 crankshaft work? What gives the GS450 the extra 50cc's?
(click to make them bigger)
Engine teardown time, and I found the problem.
OK. First thing you're going to notice is the amount of **** inside the cylinders. I'm pretty sure that was this engine's downfall. All that dirt and hair and **** was just laying inside there, eating away at everything. Although, the cylinder walls do look pretty good to me, and all the bearings seem tight EXCEPT..
#2 piston. (Facing forward, the cylinder on the left). The main bearing on the crankshaft is ****ED. How do I know this? Well, when lifting up and down on the piston, the con-rod/crankshaft journal has about 1/8" of play and makes an audible "pop" every time you do this. Now imagine that spinning at 7,000 RPM and... You get the idea. Basically, the crankshaft and conrod wanted to make sweet love to eachother, but everytime they got close, the main bearing kept cockblocking. "I've had enough of this" said the conrod, and with one mighty thrust it punched the bearing in the face, destroying it and thus securing the rod-on-shaft but****ery.
...I feel dirty.
...
...
Moving on, here's what I'm thinking happend to cause this:
Most likely a piece of dirt got inside the engine and clogged the oil passage for the main bearing, starving it of oil and blowing it up. Ever other part of the engine seems well lubricated and smooth (the camshaft caps even fissed out high pressure oil when I took them off). After blowing up, it got so much clearance that it lost oil pressure completely and that's why my oil light came on.
I have not split the cases yet and I'm not sure where to go from here. These are my options:
A) Scrap the entire bike and start anew.
B) Find a used engine somewhere (gonna be $200+)
C) Fix it. How do I fix this? I imagine the connecting rod and crankshaft are both fubar, so I would need to find a used crankshaft & conrod. Would a GS450 crankshaft work? What gives the GS450 the extra 50cc's?
(click to make them bigger)
only thing i have figured so far was that bearing was either under/oversized and packaged wrong or maybe even defective material or some such thing. I lubed everything and measured everything on my first rebuild. I'm a machinist by trade and i got access to all the good tools 
. I'm from ohio not idaho. If your going to rebuild I'd check in the for sale/parts section and even do a search on ebay. I got quite a few parts for mine there. if this motor is really all that crappy inside I'd agree with sqdancerlynn and look for a good used motor complete and part out your old one for good used spare parts for future use.
. I'm not sure exactly what cycle you got.
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