TZ or was it TD road racers had the pump running with no cable roller or plate so was giving full stroke on all throttle positions I guess to be super safe on a closed throttle when liable to nip up going into a corner, but pump speed still controlled by revs. They had 20 or was it 16-1 mix in the fuel as well. No wonder they'd foul plugs on the start line.

Exactly.  Closed throttle volume is controlled by shim stack.  Off closed throttle volume is controlled by cable adjustment.

Anything else is pure BS.

If the throttle is closed and you're coasting downhill with the clutch engaged, the engine RPM corresponds to your downhill speed, so the pumps are short (like at idle) but more rapid, being controlled by the worm gear. Am I wrong?

Wasn't gonna post this but i've typed it now so here goes.
Hey Tom, sorry i must disagree & I'm gonna get roasted here lol.

I Quote--so the pumps are short (like at idle) but more rapid, being controlled by the worm gear.

In "my opinion" there's no way the worm gear can suddenly speed up the strokes because you closed the throttle "be they minimum delivery" strokes.

'I say' if you had the motor on full throttle--well any speed you like-- the number of up & downs would be the same at "that constant rpm" even if you flicked the cable off & it returned to minimum delivery.
Same number of strokes just shorter with no cable so less oil.

Ok its now an oil pump thread--well it was anyway but!!.

No roasting here... I just don't understand how the stroke count is not increasing when coasting downhill with the clutch engaged, and throttle closed. The engine is turning at the same RPM it would if you were going uphill at the same speed with the throttle open, so the worm gear is turning faster as well. You get the same stroke count at any given RPM whether you are coasting downhill with the clutch engaged, or going uphill with the throttle open. The only difference is the stroke length.

For example, when going uphill at 30 MPH with the throttle open, you have a longer stroke, but the same stroke count you would have going downhill at 30 MPH with the throttle closed, but with the minimum stroke length. So you are not getting as much oil going downhill, but more than you would if you were coasting with the clutch disengaged, and the engine at idle RPM. Stroke speed is mechanically tied to engine RPM, no matter what the throttle position is. Stroke length is tied to throttle position, no matter what the engine RPM is. Two separate operations working in concert to keep the engine lubricated.

 I actually think we all agree, but we're just not communicating. It happens online a lot 

I don't remember the approximate ratio the autolube pump delivers at idle...  too lazy to look it up right now but it's something like 100 or 120:1.  At full throttle it's something like 16:1.

That's one big advantage of autolube.  It can save oil under lower load running conditions that don't require more oil. 

Another big advantage is you don't have to mess with mixing oil into the gas which is a hassle out on the highway. 

At high rpm and closed throttle?  Autolube is going to deliver a miniscule amount of oil to the engine.  You've cut the oil way back to almost nothing.  Yes, the oil amount is proportional to RPM but it's still very little.  Which is why many riders will pull the clutch and blip the throttle on a long downhill...  gives the engine an extra shot of oil.

The fuel (and with premix, this also means the oil) doesn't stop flowing with throttle closed and high rpm...  the high vacuum is going to pull more fuel through the idle circuit than it does at idle and there's comparatively a lot of oil in the premix fuel...  So the reality is that the engine might actually get more oil at closed throttle with premix than it does with autolube...  (I always thought that might be the reason Yamaha always recommended using premix WITH autolube on the early MX race bikes and Enduros converted to race.  Until Yamaha eventually stopped using autolube on the race bikes and went to premix only.)  

Fighting to seal my oil pump on my DT250, which also was still leaking after several tries with different seals ,found out, the problem was the tiny inner seal, sitting on the shaft. The seal kit I ordered first didn't contain the right seal, so I ordered it somewhere else   Inside diameter,  if I remember right,,was 5.5mm.
But be careful , don't pull out the shaft completely.  There are 2 tiny springs, putting pressure on 2 tiny blocks,  working like a ratchet. They will fly away. Even if you find them, to re-attach them is almost impossible .
Don't ask,  how I know...

Yep i agree TomP. We're probably all thinking similar but interpreting it different into text. Maybe we'd better leave it there haha.

MarkT wrote "Which is why many riders will pull the clutch and blip the throttle on a long downhill...  gives the engine an extra shot of oil."

I am one of the many riders that does this 

I've been trying to find a scientific paper about "oil migration" through a two stroke engine... I found it online years ago but now have only been able to find other articles that talk about it.

Basically, they put radioactive isotopes in the oil and then were able to measure the migration time through the engine and out the exhaust.  If I remember correctly they also measured a ton of other factors like the residual oil in the crankcase at different premix ratios.  But that could have been a different study. 

RPM was the major factor for needing more oil if I remember correctly.  The engines needed very little to no added oil at idle speeds and the "migration time" was very slow...  a sufficient amount of the oil tended to stay in the bottom end which is where it was needed most.    As RPM increased, the "migration time" sped up and more oil needed to be added to keep a sufficient amount in the bottom end. 

I'm pulling these numbers out of thin air but it was something like a given engine only needed 120:1 at idle...  say 40:1 at 5,000 RPM...  and 16:1 at 10,000 RPM.  

If I remember correctly, the most counterintuitive result was larger displacement engines required less oil at the same RPM than smaller engines? 

Oh, and the bore and rings don't need much oil at all...  combustion chamber would be happiest with no oil...  it's the bottom end that starves for oil first.  Which might explain why a lot of friends I had with motocross racing 125's went through big end rod bearings after switching to a high-zoot "racing oil" that you could mix at 80:1 or even 100:1?  They didn't seize more pistons...  they just went through rod bearings much faster.  Bottom ends were probably starved for oil with the lean oil mixtures?  After his 3rd crank on his Honda CR125 Elsinore in less than a year, my friend Fred went back to "normal" oil at 16:1 or 20:1 and crank bearing life went back to normal.  The larger engines didn't seem to be a sensitive to the lean oil ratios...  but max RPM on the larger MX bikes was more like 7,500 and not 11,000 plus like Fred's modified 125 Elsinore.