2 stroke oil

Question do you have to re jet when going from regular 2 stroke to synthetic.I switched to synthetic and have lost about 2 miles per hour and the motor seems to four stroke on the top end more . I checked the plug and it looks like a dark tan widened the gap a bit runs good in the low and mid range .

The gap I changed from .28 to .32 and I'm running a 32:1 gas oil mix now .

I was running 24:1 with a standard 2 stroke oil.I did change the main jet to a 68 I'm going to try a 66 to see if it cleans it out on the top end.

Thanks yeah I think the 66 will be close .