IMHO the bottom line is that for average trail riding, or scooting around town, with the clever way the Yamaha autolube is designed to operate, your engine will be very happy. Racing is another story.

Well said Tom!  I think most of us can agree on that!

The only thing that bugs me a little about Yamaha's "Autolube" is their contention that it was it was a "breakthrough" in two stroke motorcycle development. 

global.yamaha-motor.com/stories/history/stories/0009.html

As many know, the Japanese Motorcycle Industry started out by copying designs...  primarily from Germany and England...  (pretty much everyone copied the DKW125 as the design was made public after WWII...  BSA and even Harley had their versions with the Bantam and the Hummer respectively...)  Mikuni carbs were originally built under license from Amal...  I believe it was Dave Meis that posted here a few years ago about the similarity of the legendary 1960's Yamaha Ascot 250 and a German model that I can't remember the name of right now.

The point is that as early as 1953 you could buy a production two stroke 250...  right out of the Sears Catalog in the USA...  that had a separate oil tank and a pump driven off the crankshaft that would deliver more oil with RPM.  The pump also had a cable connected to the throttle and would deliver more oil as the throttle was opened. 

Yes, you could get a bike with "autolube" in the USA more than 10 years before Yamaha released their first production bike with Autolube!

www.searsallstateriders.com/model/810.94180.html

I just found a good video showing the details of the Sears Allstate (Puch) 250 automatic injection oiling system available from 1953 to about 1969 from Sears in the US. 

The Yamaha Autolube system is more refined and in many ways better than the Puch system...  just as arguably the Mikuni was improved over the Amal...  but Autolube was not something Yamaha "invented". 

MarkT very interesting Thanks for sharing and your knowledge 

Interesting stuff, and that Puch 250 is very cool! It has 2 pistons in one head, that share the combustion chamber. Apparently the front one slightly lags the back one, and the exhaust exits from the front one, as fresh gas enters the back one.



Screenshot of the engine design from the video:

Back in the "60's or early "70's i had the cylinder off one of those at work.
Can't remember why, maybe base gasket. I seem to recal it being very heavy & awkward.
One of my workmates also had one of his own.

The seal from Amazon arrived early today (Monday, it wasn't expected until Wednesday) and it's genuine Yamaha. I installed it, primed the pump, then rode about 10 miles. No leaks so far, and the prime wheel isn't getting oil around it, so we'll see...

That's good.
Just looking at where the blead screw is it's higher up than what i was remembering so must be pretty near full to the top when bleading on those.

Yes, I think the pump is pretty full when you bleed it to the screw, but I also remove the line from the cylinder, and with the throttle open pump it until oil comes out of the banjo fitting,, then reattach it. Probably not necessary, but it makes me feel better. 

Update: have 35 miles on it and it's beginning to accumulate a bit of oil at the bottom again, but the prime wheel doesn't look "juicy" like before. Kind of looks like the banjo fitting on the pump may be weeping at the gaskets. It's snug, but the gaskets are the original black fiber type, and I don't want to over-torque it. Next week I'll see if a good local auto parts place near me has some. Also found the Harbor Freight gasket pack option on another thread, and may run by there and grab that. Partzilla has copper ones, and I guess they switched to that?