I have a 72 yamaha LT2 (American import) with auto-lub. The manual says engine oil- SAE 30 2-stroke oil. Can anyone recommend the best oil to use please

Yamalube 2S

I'm running amsoil interceptor to keep things clean

Thank you for your recommendations. Can anyone advise approximately how much oil should be used per tank of fuel.
my run yesterday 40-50mph for 36 miles round trip seemed like it used a lot but have only recently got it back on the road after buying as a non runner- and was the biggest single run so far. Thanks

Sounds like a nice ride!
the only quantitative way to measure oil consumption that I am aware of is to look up spec in tech library typically described in cc per 200 turns with throttle pegged and to capture output in a graduated cylinder. If displacement is too low then your pump has issues. Not an expert but couldn’t imagine correct pump exceeding specified output unless something has been modified since it’s a positive displacement type of gizmo, I would be concerned more about not enough oil!

I got a nice graduates cylinder on Amazon for less than $10
www.amazon.com/dp/B00ARJOUZU/ref=cm_sw_r..._encoding=UTF8&psc=1

40 to 50 mph is a fairly high speed run on an LT2...  I would expect to use about 1/3rd of the tank of oil per tank of gas at that pace.

The interceptor amsoil that I'm using seems to be very thin. Wont the pump be pumping more oil since its thinner. And the factory recommends 32to1 ratio on pree mix but amsoil mixes at 50to1. So wont the pump also be putting out more oil than the bike needs because its sythetic and mixes at smaller ratio.  Thing is im pree mixing at 40to1 right now until I fix my oil pump.
thanks for any input. 

Yamalube 2S is now 20w... I'm not sure Yamalube even existed until 75 or so.

They found 30 to be too thick at freezing temps.

And yes, not always smart to use synthetic designed for "lean" ratios in a system designed for "richer" ratios.  Amsoil should be able to tell you if 16:1 or 20:1 is okay with that oil.  (That's about what pump puts out max)

I devised a very simple way to confirm the pump functionality as well as the volume injected into the intake stream without tearing the skin off my finger from turning that white wheel for half an hour..  It's a tight fit against the case on a 125

The 1970 AT-1 in question had been running on premix with the pump removed for several years before it was parked in the barn for almost 30 years. No longer a youngster wanting to be like the "cool" pre-mixers,  I wanted to replace the pump and go back to allowing the Yamaha engineers take care of such things as oil ratios. I sourced some parts and lots of help and advice from MarkT,  (thanks Mark) and got to work.

As it was running pre-mix (32:1) I had half a fuel tank prior to the pump test.

1. Pump cover off to expose the white pump primer wheel.
2. A red mark was placed on the pump primer wheel so I could count the 200 revolutions needed for the test (Sharpie)
3. All the oil tubing was replaced and the pump to cylinder end left disconnected and cut a few inches too long. If you 
    remove the banjo fitting to conduct the test, plug the oil input port to avoid the air leak and resultant lean condition.
4. Remove the pump prime screw and allowed it to flow for a bit to fill the gear cavity
5. When satisfied the pump was full ( or nearly so)  the prime screw was reinstalled
6. Sourced from any local pharmacy, a 10 cc syringe. remove needle and plunger
7. attach the tubing to the port on the syringe barrel
8. Hold, tape or otherwise fasten the syringe barrel in an upright position beside the carb/ cylinder
9. Pull the oil pump cable up to the full throttle position and clamp the cable in that position with a hemostat
10. Fire it up and when the first "pulse' of oil appears in the bottom of the syringe, start counting the rotations of the     
      primer wheel with the help of the red mark

At idle speed, the pump wheel is not turning very fast and is easy to count the revolutions. when you get to 200, shut the engine off and have a look at the level in the syringe. The AT-1 spec is just under 10cc @ full stroke and 200 revs. Mine was exact on the money. I buttoned up the banjo union and went riding. The pre-mix plus the auto-lube made for a bit more smoke, but nothing like what you would expect. As the pre-mix in the tank has been burned away and replaced with straight pump gas over several fill ups. The smoke has all bet dissipated. A small bit of smoke when it's cold, but after it warms up it is not visible at all.

There... This helps ease my doubts about the Yama-lube system.. I'll take mine out and verify alls in order first.. Thank you for the info!
Sneezles61