I just rebuilt a 92 650 and ran 40:1 mix for the first 3 hrs. Thank goodness I did because my oil injection line wasn't connected properly to one of the throttle bodies. Mixing saved my brand new motor.
Only takes one time like catfish to make you a firm believer!! I always use 50:1 in that first tank, and convinced a buddy of doing the same on an 800 RMK we were working on. He had a bunch of crank work done to the engine, we got it out on it's first ride, the inlet to the oil pump fell off. It's a pressed in part and it failed. We stopped at about 5 miles, he had oil all over the place in the belly pan, but because he had premixed that first tank, we plugged the tank and finished the day's ride.
btw... if your pump fails to pump oil, you will make it 4.5 miles. Trust me on that one
I coming of a top end rebuild. It's not science, but it's what I've read around here.
First 5 gallons was 50:1 premix with oil injection.
Second 10 gallons was at 100:1 premix with oil injection.
Third 5 gallons is at 200:1 premix with oil injection. << I'm here right now.
Forth 5 gallons with 10oz of Seafoam to clean up.
Fifth 5 gallons with 5 oz of Seafoam to clean up.
Install new plugs.
So far, pretty smokey upon start up. When it's warmed up, not as smokey. Plugs look a little brown but hey, it's expected. Starts on third pull on cold startup (dead starter so I have to pull).
No WOT's yet. Up and down on the throttle up to 7500 RPM and back off. WOT's coming soon.