Ok this might take a little while:
I ran my 550 all last summer and it was great, but toward the end it started to bog down and eventually gave out. So as fall set in, I checked the compression and had terrible compression in the back cylinder. So i rebuilt the topend and got new gaskets for the intake manifold and exhaust manifold. But, when I went to start it for the first time after the rebuild it was running pretty lean--seemed almost like WOT but it probably wasn't--I was in my garage so I'm sure it sounded louder than it really was. Regardless, I need to know what to do. I've been doing a few searches but there seems to be mixed emotions--some people telling me to just do a leakdown test, some just telling me to tear it all down and replace the crank seals, and some telling me it's probably leaking air from the intake. I feel like the third would make the most sense because that's all I've messed with and it was running perfect before I lost compression. So, any ideas? Thanks