Why do some M8's sump and others don't?

[rich1]

Maybe there is no answer. But if there were a design flaw wouldn't they all sump? And that appears to be true no matter which version of the oil pump is used.

[Hossamania]

It was mentioned that perhaps most are sumping, but most riders don't ride hard enough for it to be an issue, or don't pay enough attention to their machines to recognize the problem.

[harleytuner]

Might not be a design flaw, might be an assembly issue, or a parts issue.  Could very possibly be a tolerance issue.  HD isn't really know to have tight tolerances, so if you have a part built to one side of the spec you might have an issue, one built more to the middle or the other side of the spec might be fine.

[bensfatboy]

If it's sumping, something is not right.

[hattitude]

But if there were a design flaw wouldn't they all sump?

Interesting thread about this very issue on another forum I read, titled: "My theory as to why some M8s are sumping"

Some apparently knowledgeable/experienced people discussing the causes. They bring up several design issues specifically related to the engine's ability when scavenging the sump oil. They mention issues with the oil pump, the case design, and crankcase pressure pulses... all being able to contribute and/or put the system out of balance and cause the sumping. Issues that, in and of themselves, won't cause sumping, but have combined to create a design that is very fragile to variances.

If they are correct, it would support why not all engines sump. Why there is no single issue that causes the sumping. And why there's, as yet, no simple band-aide the MoCo can find to fix all sumping.... some "fixes" work in some cases but not all...

A couple posters, involved in M8 performance upgrades, mention that M8 cylinder bores on MoCo stage kits are a frequent problem. They claim they have found many out of round, causing excessive blowby pressures that can affect scavenging, then leading to sumping. That could be why some performance shops have been able to add big bore kits (with their own boring or cylinders) and don't get sumping even with the original OEM M8 oil pump... and yet the problem first showed up in MoCo big bore kits....

Anyways, if their observations/conclusions are accurate, it appears to me that the MoCo is attempting to tweak the oil pump to increase it's scavenging ability and efficiency to overcome sumping, rather than fix design issues that cause it... a cheap band-aide, if you will, to cover all the wounds......

It's an interesting thread, over my expertise/experience level, but I've wrenched on my own HD motors enough, that I can understand and follow their discussion.....

Not sure I'm allowed to paste an URL to another forum, or I would....

[klammer76]

But if there were a design flaw wouldn't they all sump?

Interesting thread about this very issue on another forum I read, titled: "My theory as to why some M8s are sumping"

Some apparently knowledgeable/experienced people discussing the causes. They bring up several design issues specifically related to the engine's ability when scavenging the sump oil. They mention issues with the oil pump, the case design, and crankcase pressure pulses... all being able to contribute and/or put the system out of balance and cause the sumping. Issues that, in and of themselves, won't cause sumping, but have combined to create a design that is very fragile to variances.

If they are correct, it would support why not all engines sump. Why there is no single issue that causes the sumping. And why there's, as yet, no simple band-aide the MoCo can find to fix all sumping.... some "fixes" work in some cases but not all...

A couple posters, involved in M8 performance upgrades, mention that M8 cylinder bores on MoCo stage kits are a frequent problem. They claim they have found many out of round, causing excessive blowby pressures that can affect scavenging, then leading to sumping. That could be why some performance shops have been able to add big bore kits (with their own boring or cylinders) and don't get sumping even with the original OEM M8 oil pump... and yet the problem first showed up in MoCo big bore kits....

Anyways, if their observations/conclusions are accurate, it appears to me that the MoCo is attempting to tweak the oil pump to increase it's scavenging ability and efficiency to overcome sumping, rather than fix design issues that cause it... a cheap band-aide, if you will, to cover all the wounds......

It's an interesting thread, over my expertise/experience level, but I've wrenched on my own HD motors enough, that I can understand and follow their discussion.....

Not sure I'm allowed to paste an URL to another forum, or I would....

Interesting...

[rbabos]

Not sure I place a lot of faith in the blowby theory. Any extra blowby will be handled by the breathers. I'd blame pump centering and based on the explained method, it leaves a lot to be desired to actually center the rotors.
Ron

[MPop]

A couple posters, involved in M8 performance upgrades, mention that M8 cylinder bores on MoCo stage kits are a frequent problem. They claim they have found many out of round, causing excessive blowby pressures that can affect scavenging, then leading to sumping.

The impression I've gotten is that the production 114s do not have sump issues, only the upgrades. Is that corrrect ? If so, wouldn't the cylinders for production and the ones for upgrades (to put it simply) all come out of the same bin ?

[hattitude]

A couple posters, involved in M8 performance upgrades, mention that M8 cylinder bores on MoCo stage kits are a frequent problem. They claim they have found many out of round, causing excessive blowby pressures that can affect scavenging, then leading to sumping.

The impression I've gotten is that the production 114s do not have sump issues, only the upgrades. Is that corrrect ? If so, wouldn't the cylinders for production and the ones for upgrades (to put it simply) all come out of the same bin ?

It was George Bryce and Steve Cole who said they have seen several MoCo cylinders out of round, causing ring seal issues. They didn't say "all" cylinders, just that it was an issue with several they had worked on...

[randyman]

I took my 2017 FLHTK in today for a front end wobble.  While there I mentioned that when I do a lot of riding it seems to lose power but the next day its right back and running great.  They said they will check it for sumping by running it hard a bit and pulling the case drain and let me know.

[harleytuner]

A couple posters, involved in M8 performance upgrades, mention that M8 cylinder bores on MoCo stage kits are a frequent problem. They claim they have found many out of round, causing excessive blowby pressures that can affect scavenging, then leading to sumping.

The impression I've gotten is that the production 114s do not have sump issues, only the upgrades. Is that corrrect ? If so, wouldn't the cylinders for production and the ones for upgrades (to put it simply) all come out of the same bin ?

It was George Bryce and Steve Cole who said they have seen several MoCo cylinders out of round, causing ring seal issues. They didn't say "all" cylinders, just that it was an issue with several they had worked on...

Steve had a kit where one of the pistons wouldn't even fit into one of the cylinders (bottom of cylinder).  It fit in the other though.  Out of round and tapered.

[kd]

A couple posters, involved in M8 performance upgrades, mention that M8 cylinder bores on MoCo stage kits are a frequent problem. They claim they have found many out of round, causing excessive blowby pressures that can affect scavenging, then leading to sumping.

The impression I've gotten is that the production 114s do not have sump issues, only the upgrades. Is that corrrect ? If so, wouldn't the cylinders for production and the ones for upgrades (to put it simply) all come out of the same bin ?

It was George Bryce and Steve Cole who said they have seen several MoCo cylinders out of round, causing ring seal issues. They didn't say "all" cylinders, just that it was an issue with several they had worked on...

Steve had a kit where one of the pistons wouldn't even fit into one of the cylinders (bottom of cylinder).  It fit in the other though.  Out of round and tapered.

I seem to remember him saying his testing showed higher cylinder head heat than normal (TC). No one wanted to listen though.

[hd06]

 Has there been any stock M8 107 with this problem.

[harleytuner]

Has there been any stock M8 107 with this problem.

Yes they're has been reports of stock 107's sumping, but i believe they are from different causes.  There was some early reports of piston jets loose in the cases that were causing sumping.  I believe they are separate issues woth tree same symptoms

[hd06]

 Ok thanks

[Thermodyne]

I think once you get past some of the shops not being up to the task of installing the kits, as in just assuming all the parts are serviceable and too much use of the air tools, there is an issue with the design.

Most people don't push them hard enough to experience any issues.  But people who wring em out for extended distances do.  And this is more apt to be people who dropped the cash for the big bore kits. 

When the engine is at high rpm under high load the balance shaft are slinging too much oil onto the cylinder walls.  Resulting on the loss of power and smoke out the pipes.  It got a lot worse or more often reported when the new Softail hit the street.  With two balance shafts slinging oil.

And while dropping the level of the oil in the sump is the quick fix, at some point it will impact how well the bearings in the case are oiled.  So just sucking the sump dry is not the solution.  The MoCo either needs to find that perfect balance between oiling the bearings and not drowning the jugs, or stop the oil from being slung into the jugs. I don't see the MoCo recasting the cases to move the shafts.  But I could see them backing down the rpm limit.  Or perhaps limiting how long it can be above x rpm.  A band aid to cover the problem up.   

This is what comes of having all of the testing down in house, and without any sort of facility of staff dedicated to the task.  If some of the development scooters had been thrashed on, they would have found this pre production. 

[randyman]

Talked to dealer they left my bike idling in shop and checked it for sumping they drained out 5 Ounces? and the spec is no more than six and it used to be 3.  Moco has given OK to dig further.  Bike is 100% stock with 4000 miles on it.