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School me about CCK bottom ends


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Old 04-09-2017, 09:27:42 PM
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Default School me about CCK bottom ends

I just bought a welder project a Miller 250 trailblazer with an Onan performer 20 xsl engine. the guy took a head off 7 or 8 yrs ago. He remembered that it was running like crap and had low compression. Ill say it is low , the pistons don't move when cranking but the valves open and close!!! The one piston form the cylinder that I can see is about half way down the cylinder. Im not even sure how that is possible, the flywheel is at the front and the cooling fan is at the back and both turn when the starter is engaged and the valves open and close. It doesn't sound like bad mechanical noises when it is cranking , spins over fairly quick but the pistons don't move. So how does this work??. I have no experience with CCK style bottom end work. I did also get a Kohler engine from another Miller welder with it which might make it whole again but I am also puzzled about how the engine attaches to the generator on that one. But first things first. Cheers Dan
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Old 04-09-2017, 09:32:04 PM
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Default Re: School me about CCK bottom ends

Busted crankshaft?
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Old 04-09-2017, 09:33:44 PM
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Default Re: School me about CCK bottom ends

The connecting rod is broke? Your gonna have to open it up and see what's up
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Old 04-09-2017, 09:43:58 PM
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Default Re: School me about CCK bottom ends

Just looking at a CCK motor it looks like the flywheel is up front, as in not mated to the gen head so the start ring gear is there. From there it looks like timing gears and then the actual crank journals for the connecting rods. So if the crank is busted past that first main bearing beyond the timing gears than it might explain why you have valve train action but not any piston movement. Just a guess looking at how its all laid out. Or both con rods went kerplewy. Which means it got oil starved.
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Old 04-09-2017, 09:47:27 PM
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Default Re: School me about CCK bottom ends

Broken rod will be the problem. I am guessing right side looking from the front
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Old 04-09-2017, 10:14:33 PM
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Default Re: School me about CCK bottom ends

Either way, it sounds like it would be cheaper to find a RV set or whatever to donate an engine to the welder. That engine you have sounds like its expensively broken.
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Old 04-09-2017, 10:35:55 PM
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Default Re: School me about CCK bottom ends

Both pistons don't move, but yet the crank turns? I never heard of 2 out of 2 connecting rods failing, but obviously something is majorly and seriously wrong. Drain oil and look closely for small metal fragments. If you have a bore scope, look at the bottom of the pan after draining the oil. Look for metal chunks.

If the rod(s) are broken, you may also have scored cylinder wall(s) too. I bet if you tear down the motor, it will look as if a grenade went off inside the motor. Hey, did you notice any fine hairline cracks in the block?

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Old 04-09-2017, 11:03:20 PM
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Default Re: School me about CCK bottom ends

Quote:
Originally Posted by TLB01 View Post
Busted crankshaft?
second the busted crank , it has to come apart for any of the things that could be wrong with it
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Old 04-09-2017, 11:08:33 PM
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Default Re: School me about CCK bottom ends

One other theory and this one is a bit nicer:

The keys are sheared. The flywheel might be dragging on the crank timing gear enough to move the valve train. If the keys are sheared it might explain why it ran like butt. It jumped time. Of course, they don't just spontaneously break. Its not a lawnmower hitting a tree root.
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Old 04-09-2017, 11:14:34 PM
Wayne 440 Wayne 440 is online now
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Default Re: School me about CCK bottom ends

It has a broken rod. I would not assume that both pistons are not moving based on looking at only one.
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