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Discussion Starter #1 (Edited)
Raptor 125 No Compression

Recently picked up a raptor 125 of craigslist for $1200 bucks. It's a 2011 so in my mind it was a good deal. First 2 weeks on the thing has great. Start's right up no problem and goes though all the gears. I did notice the machine did like to pour white smoke allot but im not sure if that is relevant to my problem. So the other day while out in a snow storm the machine simply started bogging down and stopped running and I cant start it since. The engine just cranks over and over and I don't get even the slightest sign off combustion. I did a very unscientific compression test with my thumb over the spark plug threads and noticed that the piston doesn't even have enough compression to push my thumb off the hole? Also it doesn't seem to be getting any fuel? The Plug is dry after cranking the motor trying to get it started.

Other things checked

1. Spark is Good
2. Carb is Clean
3. Valves were adjusted (in spec)
4. Doesn't Seem to Be getting Fuel/ Almost no compression?

Is it possible that the top end just needs a rebuild? aka no compression?
 

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Are there any modifications (air box or exhaust)?
If so, I suspect it has been ran hard and very lean.
 

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I may be getting older, but I refuse to grow up!
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Is the coolant level low? It could be a blown head gasket (white smoke), bad rings, scored cylinder, hole in the piston, bad valves, etc. Either way, it's gotta come apart. Sorry.

WELCOME TO THE FORUM.
 

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Is the coolant level low? It could be a blown head gasket (white smoke), bad rings, scored cylinder, hole in the piston, bad valves, etc. Either way, it's gotta come apart. Sorry.

WELCOME TO THE FORUM.
Air cooled.

I'm leaning toward melted piston/scored cylinder.
 

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I may be getting older, but I refuse to grow up!
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Air cooled.

I'm leaning toward melted piston/scored cylinder.
If you need a new piston, bump your compression to 11:1 or so if available.
 

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Discussion Starter #7
Will do. I noticed that when the flywheel pointer is at top dead center the camshaft sprocket pointer is a little off? Could this potentially be the issue? Just rechecked the valves everything is still in spec.
 

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I may be getting older, but I refuse to grow up!
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Will do. I noticed that when the flywheel pointer is at top dead center the camshaft sprocket pointer is a little off? Could this potentially be the issue? Just rechecked the valves everything is still in spec.
They don't always line up exactly. But 1/2 tooth or more may be cause for concern. Like a stretched chain and/or a jumped tooth. BUT, I still suspect a bad piston/cylinder.
 

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I may be getting older, but I refuse to grow up!
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Nice.
 

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Discussion Starter #11
Just redid the top end. Let it warm up for about 10 minutes in the garage and took it out. And the dam thing seized after about a half hour. Engine still spins freely but I think I broke a ring. I give up im putting this junk on ebay.
 

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I may be getting older, but I refuse to grow up!
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Where are you located. I'd be interested also.
 
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