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Discussion Starter #1
I recently bought 03 trailblazer not running (claimed carb was gummed up). Cleaned carb and still no start. Ran compression check and only had 60 lbs.

Tore apart and found it was out of round at 74.1 mm. So couldnt be bored. Went to shop and bought used cylinder that was checked and found that it was slightly over stock so bored to 72.5mm and matched to new piston and rings.

Installed these and still have no compression. I installed rings the only way they fit on with writing up and the ring gaps toward the carb. All new gaskets used and wrist pin bearing.

Pretty frustrated. Only part of top end not replaced was head.
 

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Welcome to the forum.

Did you align all of the ring gaps? If so, that's your issue. The ring gaps need to be staggered.
I know next to nothing about engine rebuilds, so forgive me if I am terribly wrong, but that's the way I heard it.
 

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Thanks!

I did stagger them, the ring pins are staggered and thats the only way they will compress to go in cylinder is if the gaps are over the pins
 

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Discussion Starter #4
Im wondering if I have a leaking head? Since that was the only reused part?
 

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I was just doing some Google searching on lining up piston ring gaps, and it seems that this is done differently on 2-strokes than 4-strokes, and that your bike is a 2-smoker.
My tiny bit of knowledge was from 4-strokes.
I now understand that 2-strokes have pins, and the ring gaps line up with those.
I also ran across some text that led me to believe that there are different types of rings and they go in a certain order, and they are shaped differently.
Found a photo to illustrate it: http://www.myronsmopeds.com/wp-content/uploads/2011/09/Piston-Rings2.jpg

But I'm afraid I am now way out of my element, so I'll just shut up before I show everyone how ignorant I am of these things.
Oops, too late. :)
 

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Discussion Starter #6
I am an idiot!!!!

I went through everything again and discovered I had only finger tightened the intake bolts. I tightened them and after a few seconds cranking and choking it lo and behold it started.

When I felt the carb before it was sucking air though the intake seal and not through carb. I can't believe I did something to dumb. Too many distractions I guess.
 

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Discussion Starter #7
Thanks for the input scoundrel! Ill finish putting it back together tomorrow and start the break in and hope everything is good. I only let run for a couple seconds just now but im glad I checked again or I would have a very sleepless night.
 

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Must have felt good when it fired up though.
 

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I have a 1997 xplorer, it lost compression and I put in a new jug,piston,head gaskets and still only 65 psi of compression. am desperately looking for idea's
 

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Discussion Starter #11
Jhayes. I would go backover everything. Check make sure rings are put on right side up. The piston is installed with ring pins towards intake. Have the cylinder and piston measured for bore size, taper, out of round. Make sure correct size piston and rings used for bore size. That head is flat and not warped. Check for cracks. Check make sure gaskets are good.
 
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