The same engineers that did the TC did not do the M8.

First an issue that I've had with the TCs.. I built a 131 ci TC early style with SnS first gen cases. What is nice about these cases is that they still used the original feed and return lines as the 5 speed twincams.. It had as sumping issue that stayed with the bike up until I had to rebuild the motor due to a spreading crank. It would sump pretty much any time the motor was run at upper freeway speeds and the ambient temps were hot. If I slowed down and let the motor idle the issue would go away. How did I fix it? Well I changed the Fueling pump to a SnS dual scavenge rotor pump.. Couple of thousand miles later and the motor runs cooler and has had absolutely no issues with sumping..

My theory as to why..

SnS screwed the pooch sort of when they designed the engine cases.. I'm sure that they had no issues with their crate motors but if you use a single scavenge gerotor pump like I did the problem occurs.. Where SnS first designed these TC case cases they used an in house gear driven pump that has a pump for the cam chest and one for the crank case.

So what cases the problem?

Well, the current designed oil pump for TCs.. They use one set of gerotors to scavenge oil from the crank case and the cam case. The problem is that there is an acoustic phenomenon that occurs in the crankcase side of the scavenge passage. It drove the engineers crazy trying to figure it out.. They finally discovered that the fix was to create a long skinny passage to the pump. It's been documented in a couple of books where the engineers mention how they finally solved the problem. The pulsations from the pistons moving up and down was un-priming the pump.

The SnS cases use a large 1/2 inch diameter pickup but don't have the issue as long as there are 2 scavenge side pumps. Use a single scavenge pump and issues occur.

Here is a picture of a set of 2000 TC cases.. See the skiny pickup..





Here is a picture of the SnS cases.. It's got a big friken hole..




As far as I know the only way to fix this is to go to a dual gerotor pump..

 

So does the M8 have a skinny pickup? Here are some pics that show the passages. Unfortunately, I don't yet have a good pick of the actual pickup, but the pic I do have does not show a small orifice..





Here is the other side..

 

Congrats this is the most concise and informative thread I've seen.Dont have a sumping or any other issue but going to Stage 111.Your acoustic resonance theory would explain why the occurrence seems greater with the increased effect of high compression Pistons!

 

Damn compelling point. HD should deputize you if this turns out to be the answer.

 

Cool story

 

very informitive

 

His spelling and grammar wasn't too bad either.

OP: thank you for the info.

 

Here is another bit of evidence. HD tried to reduce the inlet diameter to the pump to stop the sumping.. The problem is that the hole is too short and likely not close enough to the inlet to do any good.





I suspect that fixing this issue is not going to be simple..

 

Interesting. Some of the earliest M8 bikes immediately became dyno test mules for Steve Cole and Jamie Long. They did not have any sumping issues. There are still reports of sumping with the 3rd generation pump. So is it same to say its more luck of the draw as opposed to which version pump you have?

 

of course it won't..they can't produce the only muffler they offer to last a year without the baffles rattling loose or their clutch switches to work as designed for a whole year of being able to start in gear..at least for us and a couple of our M8 owner friends..QC seems to be an issue..hate to be a pessimist and pile on..but up until our M8's (which at least provide a more enjoyable riding experience) we just didn't have recurring problems like these with our previous Harleys..something to be said for mature and refined vs new and improved I guess..but in all fairness, we haven't yet had to deal with the shifter linkage issues on our M8's which damn near everyone we ride with had on the pre M8 models..take the good with the bad..apologize for the OT rant