Not a Yami, but damaged none the less...

killerklown

killerklown

Member
Joined
Jul 16, 2004
Messages
523
Age
48
Location
Wisconsin
700 Wildcat. Recent rebuild. Had cylinders mi'c and diamond honed. New Wiseco pistons, Boyeson reeds, all new CAT gaskets. Pre-mixed first tank of fuel. 400 Main jets. Always warmed up before driving. Alternated throttle position, no extended wide-open lake runs. Premium pump gas always. See the pics for damage. Pitting on head and piston, scoring on intake side of piston. Gassed up after a 30 miles cruise yesterday. Small back fire at the gas station, then ran for crap under 5000RPMs. And lost all ot of torque. What ya think could be the issue?
 

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Looks like a bearing came apart. I have had 2 dirt bikes that the crank bearing came apart and it looked the same as yours does.

Look at the crank breaing in between the connecting rods, some times you can use a small screw driver to turn the bearing to see all the way aroung it. Since you did not say anything I am sure the wrist pin bearing is fine.
 
Something deffinitly got in there. Broken ring, needle bearing, etc.
 
flatblack97 said:
looks like the ring broke and pieces got on top. Why would the ring fail so quickly though??
Click to expand...
Could be that the ring locator pin came out and allowed the ring to spin and catch a port? Maybe the ring end gap was incorrect? Or it could have been a bearring and not the ring at all?
Could be from something left in the cases from the rebuild. Why was the motor rebuilt?
The world, may never know!?!? LOL
 
I agree with both flatblack97 & Sno-Xr about it being a broken ring. Did you look at the cylinder any clues there, could you see if the ring caught on one of the port openings. It would be easy to tell if the ring pins came out.
 
Those cat 700 twins were not known to be reliable.

Something sure went south on that one though. What sux the most is that you just rebuilt it.
 
I see there are 2 small square shaped grooves, about 1/4 inch long right above one of the ports. Like a piece of something was sticking out on the piston and scraped upwards. I assume they will line up with the deeper ones on the piston! I Assume whatever that was finally made it's way above the piston and bounced around. Or maybe it started at the top? There was a little pitting in cylinder head when I put it back together...I don't see any pieces out of the ring, and the pins are both still there. Rod bearing looks good, everything turns over really smooth.
So maybe one of those old pits got hot and detonated a piece of metal off, into my moving piston?
Does the wash look alright to you guys?
 
So it looks kina rich to you too as well? What's up with burning down rich? Any significance to the most damage being on the intake side?
 
the thing is i see no detonation/melting of the piston from a lean burn,tells me a mechanical failure then.
 
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