"running lean" normally refers to an incorrect air/fuel mixture - too much air - not enough fuel  - being delivered to the combustion chamber by the carb or fuel injectors.  A little bit lean won't hurt anything. Too lean a mixture will cause the engine to run hot and can cause damage over time. A two-stroke run lean is prone to seizing.

A fuel flow restriction between the petcock and carb is not really the same thing. If not enough fuel is getting into the float bowl the engine may run like crap, esp. at high speed, but it isn't likely to suffer any actual damage.

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I gotta tilt toward "whatever else was going on at the time". What happened with the petcock was basically just "running out of gas".
In a four stroke with adequate oil pressure serious engine damage just from fuel starvation seems pretty unlikely to me unless the engine is really being flogged beyond reason. If a ring sticks because the engine stalls in such a case the damage comes from a combination of heat and a sudden lack of lubrication as the engine spins to a stop, not from a lean fuel/air mixture.

Probably just semantics; and it won't make much difference to a guy who just trashed his engine, but "running lean" and "fuel starvation" are two different things IMHO. That's what I was trying to convey in my original answer.

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This is what prompts my question, how is it that running lean is bad for the engine? Not enuff combustion to provide even stroke?
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Running lean will do damage only if the engine is being worked hard, like needing WOT going up a long mountain grade on a warm/hot day, or pushing it 80+ mph on a warm/hot day.
If/when doing that the piston is getting hotter and hotter, and thefore getting bigger, and pushed to the limits to the point of the piston skirt clearance becoming zero, could seize to the cylinder wall, or worse yet, melt the piston. Un less you were really horsing it hard at hi speed, and warm/hot weather, and you didn't notice any bad running condition, you can bet your life you did not hurt it at all.

Raydawg, as far as your petcock's lever position having anything to do with your pops, who knows?   It could, perhaps ....  you mentioned pops when you were running out of gas, but didn't say about when you gassed up to the full tank condition.

You haven't even said what sort of petcock you are running nor which positions you were in between when "I was just enuff outta plumb to restrict the flow a tad".

If you were restricting fuel flow with your petcock lever being out of position (starving your carburetor) then you could be running the bowl level way down low which will give you some pops and it can cause you to run lean at whatever ongoing speed rate you were proceeding at.

And every time you hit a hill, your piston temperature went up higher than normal, the crown/cylinder portion of the piston (the ring area) expanded more than normal and stressed your oil film up there at the rings more than normal.

Running your engine in fuel delivery starvation mode is a feedback situation you see -- your bowl goes low, fuel being sucked up by the jets decreases, your motor starts to slow a bit so what do you do?  

Your hand says "more speed" at the twist grip, your butterfly opens bigger, the diaphragm raises the carburetor slide more but the fuel delivered doesn't increase because you are fuel starved down in the bowl and there isn't any more to be delivered.   The mix ratio gets whacked, going way way to the lean as more air is delivered by the slide going up but no more fuel is getting sucked up by the jets because the bowl level is so low it isn't there to be sucked up.

Your carb is then continually mis-mixing the fuel ratio for your stated 50 miles and your hand keep making it worse by increasing the twist on the throttle whenever you hit a hill ....

And your piston crown temperature keeps going up and your piston ring area keeps growing bigger and bigger.

oldNslow wrote on 05/26/13 at 06:22:46:


Thank you....  

And just to clarify once again the issue I had. I don't run hard, or long....just ask my wife (sorry   ) and I only noticed the popping on decel, it seemed a bit more than norm, but in no way was I running long enuff, or in a manner my bowl was ever in danger of going dry.
Oh, and yes OF, I still have the factory vacsucker on, will till after my warranty expires, then off she comes, and doing a versy too