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I just did a compression test on my sled and I was a little dissapointed. 139 lbs both cylinders. The sled is a 02'zx800. I am looking for some opinions on the best way to do a compression test. Do I do it hot or cold? Also what should my compression be for this sled? Thanks
 

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It really depends on your gauge. Some will give higher
readings - some lower. What you want to make
sure is that you are less than 10% apart from cylinder
to cylinder and you have a decent compression.

I would say 139 is very decent. I believe mine was in
the 135 range after the piston recall. I'm at 150 now
but I run a different head. Again, that's with my gauge.
I've heard of another at 170 and others at 125.

Hot or Cold?? I've heard arguments for both.

Put the gauge on and hold the throttle wide open
and pull it 5 or 6 strong times. This should give you a true
reading.
 

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I was at 140 before piston recall and it is at 150 after the recall, it sounds a little high to me but i have checked it with 2 different gauges
 

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I checked the compression on my sled a couples days ago. I'm not sure how I should read it.

When I pull over engine, the needle on the gauge bounces up to 140-145 and then stops at 110 then I push the button on the gauge to reset. I do this on both cylinders with the same result. Is this the way the gauge works? Do I read the compression at the highest point?
 

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You don't want to reset the guage after every pull. Pull
it for 4-6 times strongly with throttle wide open and
I'll bet after 4 times it won't move any higher. This is
your final compression.
 

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139 lbs if just fine on the 800 twin. Right where mine was when it was stock.
 

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LadyK's 02 800 mxz gade is 140 lbs both cylinders with 5000kms/amsoil

I just checked my new 03 mxz800 gade with 1.5kms on it and the compression is 130lbs both cylinders. Heres my question is my compression going to go up or down after breakin. I would think up after the rings seat.
 

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Permafrost: Your compression may go up a little...You may want to check a measurement though...Measure from the top of the cylinder sleeve down to the very top of the exhaust port on both motors to see if that dimension is the same...if the exhaust port is a little higher on one motor than the other you may have a difference in compression...also check to see if you the same thickness base gasket on both sleds. I hope this helps...Al
 

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139 is fine. However, you want to test the motor when it is warm, not cold. Hold the throttle wide open, and pull it over 5 times. Make sure the pressure is close on the two cylinders (within a couple of psi of each other). Also, use the highest quality guages you can. Take a pass on the $15 special in the "tool bin" discount pile.
 
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