Super low compression

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Liberty_Jesus

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I put my raptor 3 back together and I can spin it by hand with little to no resistance. It has a new head gasket. Could the cam be in wrong? I lined up the two dots but is there something more? Could I have oriented the rings wrong? It used to have ok compression well at least more compression now there's no resistance when I spin it by hand. What could be the issue? It does "run" just it idles then when I full throttle it it doesn't rev up at all.
 
Brianator

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You could've put the compression (top) ring in upside down, or yes if the ring ends gaps are lined up that could also do it. Most (albeit not all) rings have a dot on the edge that faces up, if not you need to try and see the taper on the edge (top of taper goes up). You're sure you put the valves back in their respective spots? Back off your valve lash so much that the valves wont even open, that will tell a story in itself
 
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Liberty_Jesus

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Solomonster212 said:
Possibly improper timing.

Does it blow excessive pressure out of the valve cover breather?
Click to expand...

I'm not at my dad's right now so I don't know but it didn't seem like it was sucking my hand into the carburetor when I hand choked it

---------- Post added at 11:47 PM ---------- Previous post was at 11:45 PM ----------
Brianator said:
You could've put the compression (top) ring in upside down, or yes if the ring ends gaps are lined up that could also do it. Most (albeit not all) rings have a dot on the edge that faces up, if not you need to try and see the taper on the edge (top of taper goes up). You're sure you put the valves back in their respective spots? Back off your valve lash so much that the valves wont even open, that will tell a story in itself
Click to expand...

I never took the rings off and made sure none of the gaps were lined up
 
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You said you may have messed up the valve seats? Did you do any porting and knick them? Give us a breakdown of everything you've done to the motor please, it will help us help you!
 
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landuse said:
Was the piston in the right position when you lined up the dots on the cam?
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What is the right position?

---------- Post added at 09:11 AM ---------- Previous post was at 09:07 AM ----------
Brianator said:
You said you may have messed up the valve seats? Did you do any porting and knick them? Give us a breakdown of everything you've done to the motor please, it will help us help you!
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Uhhhh I replaced the spark plug, drained the oil, cracked open the crankcase cover, removed the head, took out the piston, took out the cam to see because it was aftermarket, I cleaned up some carbon buildup around the valves and on the head with steel wool and wd40 if I remember right (the valves were in and all the way down), I put a new head gasket on and put it back together.
 
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I stand by my statement to back the valve adjuster nuts off until the valves wont move when turning the motor over to see if you're still suffering from a serious lack of compression. It's a quick easy experiment
 
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Brianator said:
I stand by my statement to back the valve adjuster nuts off until the valves wont move when turning the motor over to see if you're still suffering from a serious lack of compression. It's a quick easy experiment
Click to expand...

Is this possible ona flathead Briggs? I thought the valve lash was done by grinding the valves?
 
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Liberty_Jesus said:
Is this possible ona flathead Briggs? I thought the valve lash was done by grinding the valves?
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My mistake, I forgot this is a flathead thread! Lol. The point was to make the valves inoperable to isolate where the issue is stemming from, process of elimination is a great diagnostic tool that everyone has in their toolbox. I do have a flathead (1969 B&S 7hp) but have yet to tear into it and learn the mechanics of it.
 
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