Originally Posted by FatBob2018

What could have changed? My guess is some extended time in a higher RPM range.

If I'm not mistaken, KeithHu is the one who said he can make it happen pretty much at will, pulling out and passing a line of cars. If it's a good long run at high RPMs, maybe that's what's happening. Could have been someone else though.
My guess is that any time spent in the high RPM range is probably causing some buildup of oil in the sump.

Originally Posted by RIPSAW

Most are from tin men who sale other bikes. Read them. Most really do not even know how much oil really runs in the sump. And Harley sure does not publish it. Lot depends on year. My old 2004 has a lip in the sump that keep almost 24 Oz's or so in the sump and cam galley for inner cam bearing lubrication.

Originally Posted by FatBob2018

My current theory for sumping is that the faster the engine spins, the more oil collects in the sump.
Those who have Stage III or Stage IV on their bikes, are probably more likely to spin the engine up higher in the RPM range more frequently than other riders, because that's where all the improvement in performance is found. Especially in Stage IV.
Steve Cole says it can happen to any bike, including stock. We've seen reports of it happening to stock bikes. We've seen reports of it not happening for 15,000 miles, then suddenly happening. What could have changed? My guess is some extended time in a higher RPM range.

If I'm not mistaken, KeithHu is the one who said he can make it happen pretty much at will, pulling out and passing a line of cars. If it's a good long run at high RPMs, maybe that's what's happening. Could have been someone else though.
My guess is that any time spent in the high RPM range is probably causing some buildup of oil in the sump. If it's only a little, then the system can clear it, and you have a problem-free bike. If you spend too much time in the high-RPM range, then the oil accumulates faster than the pump can clear it, reaches to the crankshaft, and you get the sumping symptoms of frothing oil, loss of power, and engine damage.

My guess is that those of us who have never had the problem, probably don't spend much time in the high-RPM range. I know that in general I don't really exceed 4000 RPM very often, usually only in a quick dash up the freeway onramp, and most of my riding time is at under 3000 RPMs backroad cruising. Under my theory, that should not lead to any sumping issues, as any accumulated oil during high-RPM maneuvers should be pretty slight since high-RPM is infrequently encountered. I have the torque cam in mine, so the main power gains are down low, under 4000, and that's where I usually ride.

Those with Stage IV especially, all the power gains come at 4500 RPM+. If I had a Stage IV, I'd ride the hell out of it at 4500-6000 RPM, that I can guarantee you. And, probably not coincidentally (under my theory), Stage IV bikes are more prone to sumping. Not necessarily because it has Stage IV installed, but more likely because a Stage IV bike is more prone to being ridden more frequently at higher RPM, thus resulting in more oil collection in the sump.

We had a post on here yesterday, someone said that riding at 5000 RPM would cause the bike to sump, period. He said he could ride all day long under 5000, no problem, but at 5000+, it'd happen every time. Now, that could be just his bike, or it could be the key to understanding the whole sumping mystery and why it happens to some but not all of us, and that maybe it has nothing to do with Stage III or IV, etc.

I guess we'd need a guinea pig to verify it for us. I know I don't want to try to force my bike into a sumping situation, but if there's someone out there who wants to test the theory, I'd think you'd want to do something like, say...

1. Check the oil level.
2. Go do 15 minutes of normal riding, keeping the RPMs below 3000.
3. Check the oil level.
4. Go do 15 minutes of banzai hell-for-leather riding with RPMs as high as you can keep 'em.
5. Check the oil level.

If step 5 shows a bigger oil level change than step 3, then ... yeah, high-RPMs probably result in oil collecting in the sump and not being properly scavenged out.

If it can be demonstrated that this happens on a never-sumped-before bike with repeatability, then we would have documented evidence of a fundamental design flaw in the M8, and that the M8 doesn't meet the basic fitness-for-purpose test, and the MoCo would have to fix it and recall all bikes so affected.

Simultaneously, it should pretty much demonstrate to riders what they need to do to avoid the sumping issue, so they don't necessarily have to fear getting stranded in the middle of the desert by a random chance event.

I'm not a mechanic, I'm a computer programmer who spends my days trying to figure out what went wrong in programs, piecing together the evidence, and then fixing the problem. So I may be totally off-base here, but it seems reasonable to me that the triggering event is high-RPM operation.

Originally Posted by 1Canuck

did you mean 2-4 oz?

Originally Posted by RIPSAW

No, but remember, I am referring to an older TC. They have a lip cast into the sump. Later versions did away with it and the M8 also does not have it.

By engineering lubrication without the splash gets a few more HP.. However the first TC's has some problems and I think Harley tried to fix the short tensioner life and inner cam bearing problem this way. When they went to the roller chain, they removed the lip. The roller like the primary once it grooves into the tensioner, rolls and no longer wears.
When I get to my laptop, I will post a picture.

Originally Posted by DTTJGlide

Your softail engine may have a lip in as you say, most likely because of the balancers, but the standard motors do not have that. The TC engine does not use "splash" lubrication for the cam bearings or elsewhere, other than for the balancer system & the cam chains.