Engine - Drivetrain

that 80w-90 will do just fine !.

I plan to change the gear oil in the rear differential in my 2000 350 Rancher since it has been a while since it was changed. The specs call for 80w Hypoid Gear oil - about 3-3.5 ounces. I have some 80w-90 gear oil that I have had for several years. Does it really matter what type of gear oil these bikes use or should I get something specific? I mean, it all comes from dinosaurs right? Thanks. 

agreed, cylinder does not look bad. you could have worn rings ?, or..bad valve guide seals ?. if the seals are bad ?, they could allow oil to seep past them, and down onto the top of piston. as for that oil filter ?..yikes !..looks like water made it into the engine at one point in time ?..looks milky too me ?. just because the main oil did not look milky, does not mean it was changed, keep in mind...an oil change cannot get all of the bad stuff out.

only other thing i can think of is either the pick up coil ?, or the stator ?. this is..if you have installed all new oem parts as you said ^^ ?. when i build my engines/projects..i never run into this issue.

So before I bought the new OEM carb I cleaned 3 OEM carbs that I had. They all behaved in the same way. I adjusted the air fuel mixture screw out 3.5 times or as much as I could before it fell out and this did not change the difficulty in starting. I adjusted the clip on the needle jet with no change in the behavior. This is why I think it is not carb issue but honestly I don't know anymore. You know how it is when you have been fighting something for 3 years you just get tired!