So disappointed (sumping)
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Joined: Dec 2005
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From: poway
HD uses what is called a dry sump lubricating system. Most of the oil is stored in an oil tank separate from motor crankcase. This system uses 2 oil pumps, a feed pump to pressurize the lifters, plain bearings, meter oil to the crank (roller) and squirt oil at different locations. A second return oil pump that has higher capacity is used to pump the oil out of the crankcase and back to the tank. The advantage of this system is that the crankcase can be made smaller as it does not need to hold all the oil. There is a small sump at the bottom of the motor that collects the oil for the return pump that only holds about 3 to 8 ounces..
Sumping occurs when the scavenge pump cannot keep up with the feed pump. The flywheels are about 8 1/2 inch in diameter discs. If the oil fills to point where they are swimming in oil, all sorts of bad things can happen. Since it take power to spin flywheels in oil, that power heats the oil and the motor can get real hot. The excess heat eventually overheats the motor and oil if not caught. Overheated oil is not a good lubricant.
What cases the motor to sump can vary. The common problem is something gets caught in the scavenge pump and either kills it or degrades it's performance. Any air leaking into the suction side of the of the pump can make things harder for the return pump. Since the twimcams, HD has used what is call a dual scavenge return pump. It's a single gerotor pump that sucks oil from both the cam case and crankcase. This pump can have issues when the suction passages to the pump become imbalanced.
Sumping is simply the lack of ability to remove oil from the motor and the motor fills with oil. If caught early, no hard will occur. Run it for 100 miles that way and the motor can be toast. The M8s seem to kill cranks.. Old TCs that made less power were easier to diagnose.
Sumping occurs when the scavenge pump cannot keep up with the feed pump. The flywheels are about 8 1/2 inch in diameter discs. If the oil fills to point where they are swimming in oil, all sorts of bad things can happen. Since it take power to spin flywheels in oil, that power heats the oil and the motor can get real hot. The excess heat eventually overheats the motor and oil if not caught. Overheated oil is not a good lubricant.
What cases the motor to sump can vary. The common problem is something gets caught in the scavenge pump and either kills it or degrades it's performance. Any air leaking into the suction side of the of the pump can make things harder for the return pump. Since the twimcams, HD has used what is call a dual scavenge return pump. It's a single gerotor pump that sucks oil from both the cam case and crankcase. This pump can have issues when the suction passages to the pump become imbalanced.
Sumping is simply the lack of ability to remove oil from the motor and the motor fills with oil. If caught early, no hard will occur. Run it for 100 miles that way and the motor can be toast. The M8s seem to kill cranks.. Old TCs that made less power were easier to diagnose.
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From: poway
Steve Cole did not state that. He did say that every M8 he has had on the dyno has transfered oil from the transmission to the primary when ran at higher rpm for a period of time, I don't remember exactly how long and that is a big thread so I'm not going to research it. There are many happy M8 owners out there that have flogged their bikes hard and not experienced it, so apparently it's not every bike.
Really!
It's still possible that all bike can do it to some extent. The theory that HD seems to believe is that the motor mainshaft seal is sucking air from the primary. Since most motors are used at larger throttle openings in the higher RPM ranges during acceleration, ring / cylinder leakage likely keeps the some of the suction in check. The reason why M8 do it more on the dyno is that the motor is run at the higher RPMs under lighter loads to tune all the map cells. It's my bet that this is where the transfer occurs, higher RPMs at lower motor loads. The is a condition you don't normally see on the street as you usually shift up a gear. Higher gears have higher loads and more ring/cylinder leakage and less chance of pulling air through the crank seal.
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From: poway
It's still possible that all bike can do it to some extent. The theory that HD seems to believe is that the motor mainshaft seal is sucking air from the primary. Since most motors are used at larger throttle openings in the higher RPM ranges during acceleration, ring / cylinder leakage likely keeps the some of the suction in check. The reason why M8 do it more on the dyno is that the motor is run at the higher RPMs under lighter loads to tune all the map cells. It's my bet that this is where the transfer occurs, higher RPMs at lower motor loads. The is a condition you don't normally see on the street as you usually shift up a gear. Higher gears have higher loads and more ring/cylinder leakage and less chance of pulling air through the crank seal.
Well Max, I went through that whole thread and made especially sure that I read all of Steve Cole's posts, I don't remember him saying anything about sumping. I could have missed it, it was a huge thread. I'm not sure of the MOCO's logic in this because if the seal is leaking I think it would add oil to the primary, that seems to be the effect of having a main seal fail. If their supposition is the case, wouldn't it be easy to prove this by venting the primary so that there is no vacuum? Maybe they have done this in their testing, don't know. If the main seal is pulling a vacuum on the primary, why isn't the crankcase drawing oil from the primary? Also, the bikes where they have replaced the main seal and put in the new spacer have mostly reported that the problem persists. I am hoping that whatever they are doing to Steve Cole's bike now cures the problem, as I am sure that everyone experiencing the problem does also.
If the seal is pulling air, venting the primary would take care of the issue..
The crankcase won't pull oil through the mainshaft seal because the area around the mainshaft seal is void of oil..
The problem is that the area around where the clutch pushrod enters the mainshaft has oil flooding the area on the hydraulic clutch models. If there is a vacuum in the primary, oil gets pulled through the mainshaft..
While venting the primary will likely cure the issue, it may be hard to find keep oil from leaking out the breather. The venting would probably only be used to validate the issue.. I don't see it as a fix.
Not sure Cole has seen any sumping.. What I'm describing above is not sumping, it's the oil tranny oil transfer issue..
If the seal is pulling air, venting the primary would take care of the issue..
The crankcase won't pull oil through the mainshaft seal because the area around the mainshaft seal is void of oil..
The problem is that the area around where the clutch pushrod enters the mainshaft has oil flooding the area on the hydraulic clutch models. If there is a vacuum in the primary, oil gets pulled through the mainshaft..
While venting the primary will likely cure the issue, it may be hard to find keep oil from leaking out the breather. The venting would probably only be used to validate the issue.. I don't see it as a fix.
If the seal is pulling air, venting the primary would take care of the issue..
The crankcase won't pull oil through the mainshaft seal because the area around the mainshaft seal is void of oil..
The problem is that the area around where the clutch pushrod enters the mainshaft has oil flooding the area on the hydraulic clutch models. If there is a vacuum in the primary, oil gets pulled through the mainshaft..
While venting the primary will likely cure the issue, it may be hard to find keep oil from leaking out the breather. The venting would probably only be used to validate the issue.. I don't see it as a fix.
Last edited by $tonecold; Sep 23, 2017 at 02:43 PM.
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From: poway
Well if the crankcase is drawing a vacuum and causing the transfer the question is what did they do different on M8 from the TC that is causing the issue. I know the M8 is using a different system breather system in the heads, I guess it could be a possibility. Hopefully they will figure it out, but every service manager I have asked about it so far says they have never heard of it. I am going to ride mine during the Street Vibrations in Reno, then I will take it to the dealer here and get the transfer documented providing it has continued to do it. I'll admit that it is somewhat disappointing that this problem has cropped up along with the sumping, but I bought a 2000 Dyna right after the TC's came out and sure enough it shelled a cam bearing. They never did a recall on that and I am sure there were many early design engines that never experienced it. All in all though, the Twin Cam is a good design that has served us well for 17 years. I'm sure the M8 will get there.
As I understand it there has been couple of the TCs with hydraulic clutches that have had the issue. It was mentioned here.. It's possible that the the transfers issue simply wasn't that bad to be noticed on TCs because the bikes without hydraulic clutches won't have the issue. I think that limits the TC with the potential of having the issue to CVOs and possibly some limited versions.
I bought a 2000 Dyna FXDX in November of 99 knowing full well that the rear cam bearings were going (fix was due in late November), the inner cam bearing was still a Torrington caged needle and that the tensioners probably have a life span of about 40000 miles. There wasn't a recall but HD would warranty the issue if it occurred up to 5 years and 50000 miles.
I don't have any issues with the M8 I have except that the clutch isn't my favorite and the valves rattle a little when the motor is real hot. I have an oil temp gauge and temps are typically between 200 and 230.. Had some oil transfer riding freeways but is seems to have stopped.
Was up in Reno/Tahoe last weekend.. Not on the M8 tho..
Cruiser
Joined: Jun 2008
Posts: 160
Likes: 40
From: San Diego
I would like to apologize for confusing sumping with transmission to primary case oil transfer. Both are in fact different and yes sumping appears to be mostly related to folks who have upgraded to stage 3/4. It's the other issue that concerns me the most (transmission/primary oil transfer) and until the true cause and solution is found it's the reason I will hold off buying an M8. Granted it's likely that only a small percentage of bikes will actually have this problem it's also still something I don't want to have to deal with. For the time being I will continue to monitor this forum and hope a solution is identified soon.
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As I understand it there has been couple of the TCs with hydraulic clutches that have had the issue. It was mentioned here.. It's possible that the the transfers issue simply wasn't that bad to be noticed on TCs because the bikes without hydraulic clutches won't have the issue. I think that limits the TC with the potential of having the issue to CVOs and possibly some limited versions.
I bought a 2000 Dyna FXDX in November of 99 knowing full well that the rear cam bearings were going (fix was due in late November), the inner cam bearing was still a Torrington caged needle and that the tensioners probably have a life span of about 40000 miles. There wasn't a recall but HD would warranty the issue if it occurred up to 5 years and 50000 miles.
I don't have any issues with the M8 I have except that the clutch isn't my favorite and the valves rattle a little when the motor is real hot. I have an oil temp gauge and temps are typically between 200 and 230.. Had some oil transfer riding freeways but is seems to have stopped.
Was up in Reno/Tahoe last weekend.. Not on the M8 tho..
I bought a 2000 Dyna FXDX in November of 99 knowing full well that the rear cam bearings were going (fix was due in late November), the inner cam bearing was still a Torrington caged needle and that the tensioners probably have a life span of about 40000 miles. There wasn't a recall but HD would warranty the issue if it occurred up to 5 years and 50000 miles.
I don't have any issues with the M8 I have except that the clutch isn't my favorite and the valves rattle a little when the motor is real hot. I have an oil temp gauge and temps are typically between 200 and 230.. Had some oil transfer riding freeways but is seems to have stopped.
Was up in Reno/Tahoe last weekend.. Not on the M8 tho..
I've seen reports of 16's doing out as well. Every M8 I've had on the dyno has transferred trans fluid. Most sump but not all. I've started checking trans fluids during and after tunes on powder bikes with hydraulic clutches and haven't had any transfer fluid yet. Probably been 6 or 8 That ice checked. If i find any that do i will report back
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Joined: Jun 2017
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From: Granville New York
what fool knowingly, voluntarily and intentionally would abuse his power train to the point of potentially ruining it and their Summer of long trip plans if they had a satisfactory and manageable workaround until a root cause and solution is determined because they are still under warranty. Thankfully they were smart enough to not bastardize their powertrain with after market performance parts while under warranty. Same fool that believes the handful of problems reported on an internet forum out of the ~100,000 sold represent the rule rather than the exception because the facts are after a year you haven't heard a single thing publicized outside of said forum. Ultimate M8 Hater.