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2005 KX250 130 psi and piston wobble/ need help

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So today I checked my compression on my 05 kx250 I just rebuilt, it is proly getting close to 9 hrs on the new top end. It had 130 psi reading on the tester. Held throttle wide open, air filter just cleaned also. And also, at tdc, I can take my finger and place it on the top of the piston and move the piston forward and backward. All I have done is take the head off so the cylinder is still on. Is this wobble ( not a huge amount of wobble) normal? I also had the cylinder re plated to match the new piston. Thanks guy!

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Something is definitely wrong . Compression should be around 200psi or more on a fresh rebuild . My 07 KX250 has 40 hours on it and still has 215psi .

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Something is definitely wrong . Compression should be around 200psi or more on a fresh rebuild . My 07 KX250 has 40 hours on it and still has 215psi .

I dont see how it could wear out that quick, I run maxima oils - 32:1, air filters always clean, I maintain it very well

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There's no way it's worn out already . You'll have to take the jug off and see what's going on . Perhaps there's a broken ring or the cylinder was honed out of spec for the piston size .

Take the jug off and measure both the cylinder and the piston diameter to see if the clearance is correct .

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There's no way it's worn out already . You'll have to take the jug off and see what's going on . Perhaps there's a broken ring or the cylinder was honed out of spec for the piston size .

Take the jug off and measure both the cylinder and the piston diameter to see if the clearance is correct .

So the cylinder when I measure it should be the same exact size as the piston. Do I measure the top, middle, or bottom of the cylinder?

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No, there is a clearance spec. Hopefully you have a service manual, the specifications are listed therein. Some movement of the piston will be evident because of the necessary clearance.

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So today I checked my compression on my 05 kx250 I just rebuilt, it is proly getting close to 9 hrs on the new top end. It had 130 psi reading on the tester. Held throttle wide open, air filter just cleaned also. And also, at tdc, I can take my finger and place it on the top of the piston and move the piston forward and backward. All I have done is take the head off so the cylinder is still on. Is this wobble ( not a huge amount of wobble) normal? I also had the cylinder re plated to match the new piston. Thanks guy!

Where did you get plated? I've seen places plate cylinders for the wrong size bore before.

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All you can do at this point is measure the piston and cylinder to see if it was done correctly . Then you'll know one way or another .

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Update: Took cylinder off and some how, a piece from the blown apart wrist pin bearing made its way to the top of the cylinder and that one piece got wedged in between the piston and the cylinder and put a little gauge into the piston and the top ring, and my dad thinks that made a bur and got the top ring compressed and stuck when it should have been sprung apart. that would explain better why I had 130 psi. Going to the shop tommorow and will talk to them and show them the little damage that was done. Will have update tommorow after noon/ evening

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Being from SC, you definately need to check these guys out. I used to deal with them when I had my shop. They are great. They actually supply many of the mail-order stores. They only deal with shops, but if you're a walk-in, they'll probably hook you up.

http://shopping.netsuite.com/ndi

Edited by SAPPERS

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Being from SC, you definately need to check these guys out. I used to deal with them when I had my shop. They are great. They actually supply many of the mail-order stores. They only deal with shops, but if you're a walk-in, they'll probably hook you up.

http://shopping.netsuite.com/ndi

wow I didnt know about these guys, thanks!

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Ok, so the guys at the shop said to take a razor blade, and scrape the bur that was made by the piece of metal that got wedged into the piston and made the top ring start sticking.

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Did you split the case after the rod bearing blew apart? Sounds like there was a piece in the crankcase that got sucked into the top-end. Hopefully there are no more pieces floating around in there or this will likely happen again.

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Did you split the case after the rod bearing blew apart? Sounds like there was a piece in the crankcase that got sucked into the top-end. Hopefully there are no more pieces floating around in there or this will likely happen again.

No I didnt split the cases, just flushed it out really good and that one piece musta been stuck in there, ive riddin the bike pretty hard since it was rebuilt so all the junk should be out of the bottom now.

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