M8 Oil Pumps and Sumping Issues - Is an uprated oil pump and cam plate needed?

Mark Hammond

Mark Hammond

Committee
M8 Oil Pumps and Sumping Issues

Came across the following information about whether an uprated oil pump is needed in an M8 to prevent “sumping” issues and felt it was interesting enough to share on here.

Alpha Performance Engines are based in Australia and are a supplier of performance M8 engines, M8 big bore kits and other M8 engine parts. They say the following info is based on their experience of building performance engines for their customers and their experience of tearing down, building and improving M8’s.

The information appears to be consistent with my own research into the subject and refreshingly doesn’t appear to be given from the perspective of trying to scare potential customers into buying an expensive oil pump from S&S, Feuling, Screamin Eagle or other purveyor of uprated oil pumps for the M8

I have no connection to Alpha Performance Engines and you’ll need to do your own due diligence on the following information if considering uprating an oil pump on a pre 2020 M8.

The following information is a direct copy of the companies most recent Facebook post on the subject.

“We still get asked about this topic daily and thought it deserved a repost. Our opinion when it comes to the M8 oil pump & cam plate still remains the same 😀

"One of the most commonly asked questions when we’re discussing performance upgrades for the M8.. “ Do I need a new oil pump and cam plate “

Again, this is just our opinion off the back of building plenty of big bore engines.

M8 Softail -

We are yet to see an M8 Softail have any issues with the factory installed oil pump & cam plate. At least 80% of the performance engines we build in-house are in the Softail Chassis. Over the past 4 years we have built hundreds of big bore engines and never witnessed an issue with the OEM installed pump/plate. If our customers have an earlier model M8 Softail ( 18-19 ) we give them the option to upgrade to the revised MY20 8-Lobe Pump but we don’t believe it’s a necessity.

M8 Touring Models - Now this is a different story.. Have we seen them sump, 100% 🤦‍♂️ There has been so many theories over the years.. Loose piston oilers, poor ring seal, oil pump design, crankcase breathers and so on. Well, we put all these theories to the test..Had perfectly true cylinders, quality ring packs, replaced piston oiler gaskets and re-tensioned, external breathers..And a few of them still sumped 🤷🏻‍♂️

In late 2019 Harley released their latest revised version of the M8 Oil Pump. It offered a 44% increase in crank cavity scavenge capacity and a 4% decrease in camchest scavenge capacity. It included a new scavenge gerotor set, new pump body and new pump cover with seal. Since it’s inception we have never witnessed an M8 Tourer with this pump arrangement installed sump, be it a basic stage 2 cam package or an all out 143ci build.

Sure there may be the odd factory bike with poor ring seal, leading to excessive crankcase pressure and oil in the intake tract, but we have not seen a bike with the 8-lobe pump installed sump.

If you have an earlier model M8 Tourer ( 17-19 ) these pumps are a worthwhile investment and very cost effective. If you have a stock engine, it’s also a good excuse to open up your cam chest and install a performance cam 😉

Again guys, this is just our opinion and we thought we’d share what we’ve found”

Home

www.alphaperformanceengines.com.au www.alphaperformanceengines.com.au

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Good write up Mark, my M8 ultra limited has a stage 3 big bore kit fitted and performance wise the needle on the speedometer races very quickly towards the big number at the very end of the speedo. It's so smooth and a joy to ride, it's on the thirsty side but that's due to a very excitable right hand. It's a 17 plate so I do keep and eye on transmission levels and any oil that has moved house to the primary side and so far everything seems OK
 
Army said:
Good write up Mark, my M8 ultra limited has a stage 3 big bore kit fitted and performance wise the needle on the speedometer races very quickly towards the big number at the very end of the speedo. It's so smooth and a joy to ride, it's on the thirsty side but that's due to a very excitable right hand. It's a 17 plate so I do keep and eye on transmission levels and any oil that has moved house to the primary side and so far everything seems OK
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I’m currently researching 124/128 kits for my Sport Glide. Because mine is a 2021 softail I wont need an uprated oil pump and cam plate and I can probably do a 124 build for about £2000 in parts. Not having to buy the oil pump and cam plate saves about £900 to £1000

However, if I put my sensible head on, I know that a fairly simple cam swap will give me all the power I would want for about 80% of the time and only cost me about £700 in parts……
 
Mark Hammond said:
I’m currently researching 124/128 kits for my Sport Glide. Because mine is a 2021 softail I wont need an uprated oil pump and cam plate and I can probably do a 124 build for about £2000 in parts. Not having to buy the oil pump and cam plate saves about £900 to £1000

However, if I put my sensible head on, I know that a fairly simple cam swap will give me all the power I would want for about 80% of the time and only cost me about £700 in parts……
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I wonder which Head will win? 🤔😂
 
To cut a long story short, we have two early (made Feb/March 2018) M8 Softails and they both blew excessive oil out the breathers, one far worse than the other, to the extent they blew out the air filter and would cover the right side cover, did a breather by-pass, vented dipstick, dropped the oil level, lead to an improvement, then eventually replaced the oil pumps with the latest ones with seal on the back, this along with the lowering of the oil level from hot full, has now cleared the problem!

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A side note, found both had frosted lifters at around only 10K miles!

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Takes a bit of worry off my mind. I have a May 2018 Low Rider which I bought oblivious of any issues with these bikes re sumping.
Fingers crossed everything is clean and oil free (exhausts, air cleaner etc) Used very little (if any) oil in nearly 4000 miles. Gearbox oil level spot on and very clean as well.
Hasn't helped my state of mind though when I found the oil overfilled by more than a pint after a service. I syphoned oil out myself. Everything seems ok but time will tell. Think I would have had breather/air box problems if this was a wet sump engine. If you want something doing...........
Absolutely love the bike though!
 
Gez said:
Takes a bit of worry off my mind. I have a May 2018 Low Rider which I bought oblivious of any issues with these bikes re sumping.
Fingers crossed everything is clean and oil free (exhausts, air cleaner etc) Used very little (if any) oil in nearly 4000 miles. Gearbox oil level spot on and very clean as well.
Hasn't helped my state of mind though when I found the oil overfilled by more than a pint after a service. I syphoned oil out myself. Everything seems ok but time will tell. Think I would have had breather/air box problems if this was a wet sump engine. If you want something doing...........
Absolutely love the bike though!
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All of my own research into this subject was indicating that the softail bikes weren’t affected by the sumping issue and the problems were predominantly in the pre 2020 model year touring chassis bikes. The Alpha Performance Engines information quoted above provided some validation of this and was a simple and concise statement that I felt would probably provide some clarity on the subject for other M8 owners.

On my own bike after I changed the air filter from the stock set up to an S&S Stealth filter, I did start to get a very small amount of oil being deposited in the air filter. The head breather bolts that are used in the S&S filters are different to the stock head breather bolts and the fumes/oil vapour are not directed directly right into the inlet tract in the same way as a stock set up, instead relying on the induction air pressure to suck the fumes and oil vapour into the inlet tract. The S&S head breather set up isn’t as effective as the stock set up and I think all I was seeing in my air filter was what would normally have been sucked into the inlet tract with stock head breather set up.

I’m confident that my engine isn’t breathing abnormally or any more than stock, however it did get me thinking that recirculating hot fumes and oil vapour through the inlet tract probably wasn’t contributing to efficient fuel combustion and performance, and probably contributing to carbon build up in the combustion chamber and piston crowns. So, I have now made up a simple engine breather that utilises the stock head breather bolts and routes the fumes and oil vapour into a small K&N type filter to catch any oil residue. The engine seems to run fine with the external breather fitted and the inside of the air filter and inlet tract is now free of oil misting.

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We used to do something similar to evos it’s supposedly better not to have oil misty air being inducted into the mixture and there were claimed gains of 1-2hp gain on the dyno by doing the mod as you have and i have been doing similar on most of my bikes since (y) :cool:
 
watchman said:
We used to do something similar to evos it’s supposedly better not to have oil misty air being inducted into the mixture and there were claimed gains of 1-2hp gain on the dyno by doing the mod as you have and i have been doing similar on most of my bikes since (y) :cool:
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Cold air in the inlet tract is generally better for performance than hot air, so stopping air that has just been heated up by the cylinder heads from entering the inlet tract, has to help performance.
 
Gez said:
Hasn't helped my state of mind though when I found the oil overfilled by more than a pint after a service.
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This used to happen with me and my mates softails whenever we went for a dealer service. Everytime overfilled. I think they just used to measure an amount and chuck it in. They probably overfilled to allow for the people that never check their oil level and assume it won't use any between services.
I service mine myself now it's out of warranty. I can screw it up myself, I don't need to pay £70+ an hour for someone else to screw it up for me.:LOL:
 
Just pulled the air cleaner off. Found about the same amount of oil as you did Mark. If thats all I get for every 9K miles I'll be 'appy.
Breathers I've come across on bikes and cars use big bore pipes connected to the air box, up stream of the filter. Oil mist is therefore trapped by the filter. Some filters use oil anyway to help do their job, but the HD system will keep the filter clean I suppose. Just seems a bit crude.
Gonna do my own servicing from now on too Rob. Just looking for the service book stamp really, and needed a back tyre fitted.
BTW, is the crankcase separately vented, or is crankcase pressure vented via pushrod tubes into rocker covers, then through those pipes into throttle body?
 
softail898 said:
There was an interesting post regarding eliminating the breather into the Inlet Manifold: search

“Heavy Breathing Road King”​

in TC Section. Good Vid.of this. 👍🏻
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Yep, thats one of the better video’s 👍 I considered venting mine into the top of the gearbox cover in the same way as in that video but I haven’t quite got my head around some of the comments on that video relating to creating two high pressure zones which effectively prevent the breather bolts from being able to vent properly (similar comments on social media where the video has been shared) I’m still trying to get my head around that one, and might vent mine into the gearbox cover at a later date as it is undoubtedly a neater solution.
 
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