2T oil issues...

[Bishbosh1999]

Recently i had to fill my little 2T supermoto with semi-synthetic as oppose to fully synthetic due to the bike running dangerously low and the shop only stocking the semi. Since I've been running the semi-synthetic, the exhaust expansion chamber is heating up very quickly (like within 5-10 mins of a ride) whereas normally it takes good long minimum of a half an hour ride to actually feel heat coming of it and the bike is making a much more nasally sound compared to its usual wail. On top of this it doesn't feel like its accelerating as quick as normal but this could just be my perception.
I was told by my bikes manufacturer a while ago that both semi and fully synthetic oils will work however the fully synthetic will work best.
Any ideas whats going on? If I've royally fucked my bike and you know it feel free to tell.
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Rieju MRT (50cc) (sold) - Yamaha WR125R

[Suntan Sid]

Drain the 2T oil tank, and refill it with your preferred oil type, end of problem. If you want to be really thorough empty the oil feed lines then prime the pump, once the new oil's in.

The only problem I know of is mixing mineral with synthetic, it can cause sludge to build up!
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"Everybody needs money, that's why they call it money!"

[Bishbosh1999]

Hopped on again today and suddenly its running smooth and has stopped overheating? Guess it could have been the 2 oils mixing or something, oh well.
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Rieju MRT (50cc) (sold) - Yamaha WR125R

[Al Swearengen]

A lot of 2t oils have thinner/thicker viscosity's than each other = meaning jetting for the thicker oil must be enriched etc.. bottles with label specifying (Premix only) are so viscous they don't pump through oil injector pipes.