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Engine Mechanical TopicsDiscussion for motor builds, cams, head work, stripped bolts and other engine related issues. The good and the bad. If it goes round and around or up and down, post it here.
M8 Sumpping was caused by.
Oil pump that was not up to the task.
However on some it was cause by the cyl oilers not being seat correctly. In assembly the screws were tightened as far as they would go but still allowed oil to seep .. Not the first time this has happen to HD.
Even with the early oil pumps some did not ever experience a summping issue.
Others after getting the pumps replaced with the HD updated late 2019 version (or aftermarket) still had sumpping they had the oil issue.
It did not effect a huge number of owners and seem to fade as a concern.
The oil pump not being up to the task is nothing new or an M8 thing.
You'd think they would get it right by now.
Fortunately we have aftermarket pumps.
The oil pump not being up to the task is nothing new or an M8 thing.
You'd think they would get it right by now.
Fortunately we have aftermarket pumps.
Of course not. That doers not change the fact it happened . It took HD 3 or 4 tries to get the pump right and became the standard install in later 2019. Latter 2019 and up pumps seem to work.
2017 for some reason were not as effected by the oil pump issue. My 2017 served me well. I did however see other I know that had the trans to primary transfer issue.
I still have a brand new S&S replacement oil pump in the bike room. I picked it up just in case I ran into an issue.
My warranty was voided right way do to the sidecar. Same as on the 2020.
A shorter pipe plug? WOW. Not sure about sumping but the bike will be a little faster since it's lighter and doesn't have that longer plug causing wind resistance. I know. Save you the trouble.
A shorter pipe plug? WOW. Not sure about sumping but the bike will be a little faster since it's lighter and doesn't have that longer plug causing wind resistance. I know. Save you the trouble.
The short plug solves the issue that the stock one would block a fair bit of the pick up port which the pump would have to work harder to extract oil through.
If too much oil was still in the case, the flywheel and balancers would whip it up and making even harder to pump through.
The stock plug is fairly tall and when they machine the case, the tool is what creates the port, and the stock plug was discovered to be blocking a fair bit of it.
That's what the short plug fixes.
Redesigned Oil pump, Seal on the oil pump against the crank case, and unblocking the scavenge port entirely was the discovered remedy to making sure the M8 wont have sumping issues anymore.
I went with the SE Camplate and kit and installed the short sump plug.
The short plug solves the issue that the stock one would block a fair bit of the pick up port which the pump would have to work harder to extract oil through.
If too much oil was still in the case, the flywheel and balancers would whip it up and making even harder to pump through.
The stock plug is fairly tall and when they machine the case, the tool is what creates the port, and the stock plug was discovered to be blocking a fair bit of it.
That's what the short plug fixes.
Redesigned Oil pump, Seal on the oil pump against the crank case, and unblocking the scavenge port entirely was the discovered remedy to making sure the M8 wont have sumping issues anymore.
I went with the SE Camplate and kit and installed the short sump plug.
Your right. It does go into the sump. Just from the bottom and fish, I thought it was in the cam case.
Here is something worth thinking about. It's not a problem about the amount of flow to the pump on the scavenge side but pressure waves that deprime the pump. Early on in the development of twincams, they had the same issues as M8s. What they found was that pressure pulses in the crankcase reek havoc on the pickup and deprime pump from since one set of rotors sucks from 2 locations.. The fixed it by making the pickup longer and smaller.. Compare the pictures..
First the M8..
Now look at the TC Pickup.. It has a long small pickup that reduces the effect of the pressure pulses to the scavenge pump.
So is a fancy plug needed that provides more flow?
IMO what HD did with the 8 lobe gerotor pump was set it up so that the rotor lobes are phased the same as far as pressure pulses go to the rotor.. Take 360 degrees and divide by 8 and you get 45. 45 degrees is the same as the angle between the cylinders.. That means the position of gerotor is the same when the either cylinder fires. The seal behind the pump only increases the average pressure in the crankcase. In doing so it increases the pressure on the scavenge pump to keep it from losing prime.. IMO the reason they are doing this is that the don't want to deal with redesigning of the crankcase..
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A shorter pipe plug? WOW. Not sure about sumping but the bike will be a little faster since it's lighter and doesn't have that longer plug causing wind resistance. 
I know. Save you the trouble. 
