Smoking and a power loss

[paydem]

www.youtube.com/watch?v=yPVP6phRFgg&feature=youtu.be

Minarelli 2-stroke. New reeds, 17.5 chinese carb, tecnigas silent pro exhaust. 2 turns out on the mixture screw, needle set on the middle because when I put in any lower (to lean it out) it bogs. Don't have photo of the plug but it looks a bit to the rich side. Even when it bogs it spits out a lot of smoke.

When engine warms up, it starts losing power. If I would put in a smaller main jet, would it help? 

By the way, I'm running 50:1 premix.

[pinkscoot]

I'm not an expert on premix but 50:1 sounds like too much oil and could be your problem. Maybe someone with more experience will comment.

[90GTVert]

I run 50:1 and I can watch a stream of smoke behind me when I have a rear facing cam, so that part in itself doesn't worry me too much. Could point to over fueling though, since it's pre-mixed.

Losing power once warm is another possible sign of a rich condition, because the warm engine needs less fuel.

Sounds like trying some different main jets (probably smaller) would be a good idea. Just because the mix screw and the needle may dislike being leaned out, that doesn't mean the main jet can't be too big. They may overlap, but they all have their own functions.

EDIT : And in reply to pink's comment, 50:1 is not too much oil. That's usually about as oil lean as most go. 32-40:1 is common.

[pinkscoot]

OOPs I got my math wrong. 50 parts gas to one part oil. These pain meds are giving me brain mush.