1987 xt600 (Need Help)

[Renhalt]

First off this bike is new to me so I have never had it running until now. It sat for two years and the tank had a bad kreen job, I addressed that and the tank has been relined with a new petcock. I also went COMPLETELY through the carb and replaced all the gaskets, diaphram, float valve, seat and filter and all the o rings. Im certain its clean, the air screw still needs some tweaking ect. I also checked the valves they'd re dead on .004 and .006, I installed a new airfilter and plug and changed the oil and filter.

Now this is what it's doing and what I have found, I really need your guys input.
First the bike starts fairly easy 1-2 kicks and it seems to idle fine and has no hesitation when I crack it!
The problem is when I put it in gear it starts stumble and miss and wants to stall. If I try and feather it and take off it will go about 20-25 then will pop and crack and dies as if it's running out of gas. Then its extremley hard to start! One thing I did notice is when in gear and it's starts to miss and pop if I shake the bike back and forth it seems to improve!

My first thought was ignition timing and I went to check it, got out my timing light and rpm gauge and removed the two plugs to check it. I kicked it over and oil came out the top inspection whole! allot of oil, now (im not sure but I don't think this side is supposed to have oil in it!? I realize oil is non conductive but I would venture to say there is a bad gasket or the crank seal is shot or the head gasket is leaking between the intake and exhaust!! IDK???

My questions are as follows:
Is there supposed to be oil in the flywheel area? If so, how in the hell you check the timing without getting oil all over the place? If not! Where is it coming from? Is there known issues that others have had?

If it is the crank seal?
Can the crank seal on the stator side be replaced without splitting the case?!!!

And what would be causing it to miss and pop and die when under load in gear?!! Neutral switch? If so, what wire do I cross to eliminate it to rule it out? Or is it the CDI.? What?

I want to add somthing that may be giving me my problems, just need your thoughts.

When I bought the bike the tach was broken, as you know they are next to impossible to find and if you do, you would think they are made of gold. So, I found a guy in AU that sells aftermarket ones that look like oem. I installed it and I don't think the plug is in tune with the stock one. Because, the high beam light is on when it's on low and vise versa. Also the neutral light stays on in gear but the backlight goes out when you put it in gear. I don't know if this would be giving me my problems as I don't know how the neutral light would play into problems? If so, what do I do to fix it?

I'm sorry for being so long winded but wanted to offer as much info as possible.

Please help as if I'm not careful I will have more money in this bike than what it's worth!

PLEASE ADVISE! Any help would be greatly appreciated!