Max

One of the most important things about the Factory Twin Cam pickup is it's position. If you were to fill the sump area with oil, it will fully cover the pickup hole with oil, with additional oil over the top of the hole. This is not the case with the M8 arrangement. The sump area is about 40% smaller on the M8 and the pickup hole location is wrong. Then to add insult to injury the plug used to block the hole for the pickup feed hole is wrong and once installed the plug itself is blocking a portion of the pickup hole.

Now with the smaller capacity to hold oil in the sump on the M8, it backs up and the flywheels are running through the oil all the time, just what you do not want in an engine! With there newest service bulletin instead of allow 3 oz of oil to come out and it passes the test for sumping they moved it up to 6 oz! This just means the crankshaft is running deeper into the oil! This is supposed to be a dry sump engine, which means NO oil for the crankshaft to run through.

So we have a crankshaft running through the oil which causes foaming
A reduced sump capacity
A mis-located oil pickup hole
A plug that blocks a portion of the pickup hole when installed
An air trap in the sump area feeding air into the suction pump
Piston oilers that leak additional oil into the engine
Cylinders that are so far out of round leaking (MoCo allows 20% leak down as good)

Then ask yourself do you really wonder why it might be sumping?

 

I'm going to agree with mjwebb here. I'm getting to the point of regretting trading off the 2014 for a 2017. While I love the bike (and I have very minimal sumpimg issues) the number of little problems coupled with this major problem, almost has me looking to trade for a 2016 Limited and building it with a Fuel Moto big bore kit.

 

I think it has more to do with cylinder leakage as Steve mentions.. BB kits are being done on seasoned cylinders with more care to the finished product than production cylinders. It would not surprise me if the "luck of the draw" has to do with cylinder leakage.. Still, the I believe the root cause is the design of the oil pump and the reason why the pump cannot cannot scavenge.. It's one pump trying to scavenge from 2 places. The stuff Steve mentions are all valid but only add to the issue.

 

quick question as i really haven't been engaged in the details of the sumping issues..but is the opinion that toe OEM oil cooled pumps are flawed in design when left stock or Stage 1? wife and I have have S1 as well as some friends that have both stock and S1 107 oil cooled engines..probably close to 100,000 miles combined for the 1/2 dozen of us and this has not come up whatsoever..all these 2017 engines have run flawlessly..if it was to become a problem would it have manifested itself by now or would we considered out of the woods so to speak, thanks..you folks have put in a tremendous amount of time and effort into these issues and appreciate all the sharing..just the scope is not super clear to some of us average folk, thanks

 

You raise a good point. I'm wondering what the percentage ratio is between sumping issues and bikes sold. That will tell us how bad the problem really is. You mentioned that there were no issues at all among the group you ride with, I wonder if that goes for 99% of the M8s out there and what we are seeing on this forum are just the few.

 

yeah, just have no clue what the failure rate would be..IIRC this whole thing started from Stage 3 & 4 kits, then went on to include some stock engines and others mentioned..got cloudy from there for me especially with all the pump iterations being discussed..doesn't change anything for us tho at this point..keep pouring on the miles as we have been and not worry..just curiosity

 

Its sounds like from Steve Coles comments there is a design flaw in the cases that contributes to the oil not being scavenged. I certainly can't argue with a man of his expertise. But if you look at the dyno charts these bikes are making good power. So how is that happening if there is a design flaw that will cause sumping? And why do some bikes run fine for several thousand miles and then begin to sump? I have asked these questions in several threads and no one has answered. I assume because no one knows. I waited on an 18 model hoping these issues had been addressed with the latest version oil pump. Guess not. Bottom line is the M8 a **** design?

 

I wouldn't say it was a **** design, I'm thinking they need to work a few bugs out. I bet the 2019 engines will be good to go.

 

My guess is you didn't understand my posts..

 

I understood them as much as a possible given I have far less knowledge than you and Steve Cole. Unless I misunderstood Steve it sounds like a design issue with the cases. What I still don't understand is how some bikes are ok for many miles and then suddenly sump. What changes? Or are they all sumping to an extent? I appreciate your time and info