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Second Rebuild with no Compression

S

snowboatboy

New member
So last winter, about the end of december, I was riding my 2007 600HO rmk and completely grenaded the motor, about the end of december, I seized a rod bearing on the crank, as well as messing the pistons and cylinders pretty good. As I started to get going on the rebuild process learned that this is a slightly common occurrence with this sled as the crank bearing aren't as good as they could be. About a month later I was completely rebuilt and ready for the first fire up. I ran it through a heat cycle and let it cool like i was told to then i fired it up just because who wouldn't with a freshly rebuilt machine. When i started it i let it warm up then gave it some throttle to spin the track and it would rev up.
So i tried to figure that out and eventually got a compression tester on it and found it had about 60 psi i thought that cant be good than tried to figure out the next thing to do.
Skip forward through summer to September I pull the head off and cylinders off and find that the new piston have scuffed my new cylinders and screwed everything up pretty good. So i called the outfit that i got the cylinders and pistons from, Millenium Technologies, and started to ask questions, they told me to send them back to them and they would check them for irregularities. They ended up honing the aluminum out of the cylinders and sending them back to me. I ordered a new set of pistons put it all back together to try again.
Same thing happens again:frusty:. Except this time I've only got 40psi. At this point I am getting discouraged and wondering what am i doing wrong. Plus I'm not super motivated to work on the mystery machine as I've got a kx500 snowbike that i picked up in the summer, but i pulled the top end apart again and found this. I've had guy i know who has quite a bit of engine experience come look at it, and he was wondering if there is supposed to be that much clearance between the top of the cylinder and the piston at tdc. And as you can see, the piston is worn, as well as one of the edges of the power valve. Any thoughts on this would be greatly appreciated, Thanks for looking.

Oh yeah if anyone wants to buy a rolling chassis with quite a few upgrade give me a shout.:face-icon-small-win




IMG_7375.jpgIMG_7376.jpgIMG_7378.jpg
 
So last winter, about the end of december, I was riding my 2007 600HO rmk and completely grenaded the motor, about the end of december, I seized a rod bearing on the crank, as well as messing the pistons and cylinders pretty good. As I started to get going on the rebuild process learned that this is a slightly common occurrence with this sled as the crank bearing aren't as good as they could be. About a month later I was completely rebuilt and ready for the first fire up. I ran it through a heat cycle and let it cool like i was told to then i fired it up just because who wouldn't with a freshly rebuilt machine. When i started it i let it warm up then gave it some throttle to spin the track and it would rev up.
So i tried to figure that out and eventually got a compression tester on it and found it had about 60 psi i thought that cant be good than tried to figure out the next thing to do.
Skip forward through summer to September I pull the head off and cylinders off and find that the new piston have scuffed my new cylinders and screwed everything up pretty good. So i called the outfit that i got the cylinders and pistons from, Millenium Technologies, and started to ask questions, they told me to send them back to them and they would check them for irregularities. They ended up honing the aluminum out of the cylinders and sending them back to me. I ordered a new set of pistons put it all back together to try again.
Same thing happens again:frusty:. Except this time I've only got 40psi. At this point I am getting discouraged and wondering what am i doing wrong. Plus I'm not super motivated to work on the mystery machine as I've got a kx500 snowbike that i picked up in the summer, but i pulled the top end apart again and found this. I've had guy i know who has quite a bit of engine experience come look at it, and he was wondering if there is supposed to be that much clearance between the top of the cylinder and the piston at tdc. And as you can see, the piston is worn, as well as one of the edges of the power valve. Any thoughts on this would be greatly appreciated, Thanks for looking.

Oh yeah if anyone wants to buy a rolling chassis with quite a few upgrade give me a shout.:face-icon-small-win




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you have something wrong with crank . Piston should be about .030 from deck. Shorter wrong rods? wrong complete crank with shorter stroke or wrong pistons assuming the cylinders are stock.. Thats totally wrong. Where did the crank come from?
 
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This is just a guess; I have heard that at least the 800 CFI-4 upper cases were 0.200" shorter for a few years ('08-'09). So maybe the 600's were as well? If so maybe they did not send back your cylinder but sent a newer ('08-'09) which would be 0.200" taller? Again just a spitball guess as I was inquiring about the case differences earlier today and that is what I was told (CFI-4 VS CFI-2).
 
I got the crank from a guy off ebay who has a race shop. I pretty sure that it is the rods are the right length as i measured it when i got it and i measured the old one as well. I also measured the stroke as well and it was what it was supposed to be.
 
I got the crank from a guy off ebay who has a race shop. I pretty sure that it is the rods are the right length as i measured it when i got it and i measured the old one as well. I also measured the stroke as well and it was what it was supposed to be.

everything cant be correct if the pistons dont come to the surface. My bet is wrong crank . if you used stock pistons and cylinders then there is no exception, Wrong Crank.thats why little compression.are your cylinders you old ones?or replaced? one of the two are the wrong part.
 
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So my dad was looking at it this morning and decided to remeasure the rods and compare them to the old crank, why I didn't think of this a long time ago I don't know. But he found the rods in the crank on my machine are actually .243 shorter than my old crank. This answers a lot of question, but it doesn't really make me very happy. Any body got any really good cheap solution to this?
 
So my dad was looking at it this morning and decided to remeasure the rods and compare them to the old crank, why I didn't think of this a long time ago I don't know. But he found the rods in the crank on my machine are actually .243 shorter than my old crank. This answers a lot of question, but it doesn't really make me very happy. Any body got any really good cheap solution to this?

They sold you the wrong Crank, it must be pulled out , Id call the guy you bought it from and raise hell.get a re man and move forward.
 
No cheap solution, gotta get a new crank.

Are you putting the pistons in right? That exhaust valve looks like the ring snagged it.

sled_guy
 
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