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Discussion Starter · #1 · (Edited)
i bought a 400ex figured it needed a new top end. did a compression test it only has 30 for compression. i put a tiny amount of oil into the cylinder. did nothing put more into it. it went up to like 60 70. so i started taking it about. i ended up finding out it has paper stuffed into the intake boot before the valves. put it back together still 30. the pin for the depression valve it still there. and goes up and down fine. the cylinder wall looks good. the piston looks pretty good. could it have 30 for compression with the burned out rings i noticed the first ring stayed compressed the 2nd one wasn't. im pretty sure it has the stock piston in it. its like a kyb or something. the timing is good. all the marks lined up. so if its posible to has 30 for compression with burned rings. or is it off timing like its trying to get compression of the wrong one. i read online that the lobes for the cam has to be facing down and they were. any help would greatly be appreciated thanks. its also a 2001 if that matters. im almost thinking its the valves but whats wrong with the valves im not sure about. cuz when i put my hand on the exhaust i noticed it push out but not much but sucked back in. but idk if that had to do with the intake being stuffed with paper.
 

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Number one - compression is always checked with an open intake - hold the throttle wide open.

Now - since you describe the piston, with a stuck ring and the way you installed the cam - go back to school - you are obviously not a trained mechanic! Sorry, but it is a bit more involved than that.

At the very least you need new rings. Why would you waste new gaskets to take the motor apart and put it back together and NOT correct the problems you found? If you had taken the parts to a mechanic, he could have inspected and measured the parts and advised you what you needed to get the compression back. Just based on your brief description, I would surmise that the engine had been burning oil causing carbon that locked the ring in the groove, but it may have been rust - I didn't get to see the parts. If there was a problem with the rings, there is most likely other parts that need replaced, like the piston pin and cam chain. Also, the primary cause of low compression is valve related - a good mechanic would have done a cylinder leak down test to see where the compression was going before taking off the first piece of plastic.

Finally - never take a motor apart and put it back together with the same rings and/or same gaskets unless those rings were just recently installed (and installed correctly) and the gaskets were never heated by a running engine. Installing used rings will cause oil consumption with almost certainty. Gaskets contain a resin that is activated by heat. Once a gasket is compressed and heated, it is useless.

Sorry to be a Pissy Patty, but if you are going to do a job - do it right - quit wasting your time. If you had the cylinder measured and honed or bored, installed new rings or new piston with rings, set the timing correctly and adjusted the valves - then you are almost guaranteed to have compression (just one of the requirements to get a running motor).
 

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Discussion Starter · #3 · (Edited)
should have been more specific i only took the head off first then noticed that.. thinking well it could posibly get that low of a number if the intake it blocked off. and that could be why when i put my hand over the exhaust when turning it over it felt like it was sucking my hand it then barely pushing it away but just about equal air. not more sucking then aire pushing.. so just to try to see if it had compression i used the old gasket because if it it did i was going to replace the piston and chain and the timing chain quides anyways. but it was the same. so then this time i took it apart i took the head anddd the cylinder off and noticed how the first ring was stuck. and to me i wasnt just so sure you could have 30 for compression with a ring like that. ik you have to hold the carb wide open just forgot to add that part
 
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