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M8 Understanding the new S&S Oil Pump

  • mickle
    mickle
    6 years ago
    Something I found informative whilst looking through the American Forums, I am waiting on one of these Pumps to arrive for my CVO.


    Could someone be kind enough to explain the "Dual Scavenger" pick up system on this S&S set up that I her about that make it better than the Fueling set up? It's probably apparent to most, but I'm not so familiar with that aspect of these two pumps. TIA.. 
     
    ....... 
    The stock pump has two scavenging pickups, one for the cam case and one for the sump in the crankcase. It only has one scavenging gerotor which is the pump pulling on both pickups. So if the cam case gets pumped dry the pump will suck air on that side which can cause it to lose prime on the crankcase side which will result in sumping. Try putting two soda straws in your mouth, one shorter than the other. When the liquid gets below the short straw it will be harder or impossible to suck liquid through the other straw as long as you are pulling through both. 
     
    The S&S pump has a gerotor or pump for each pickup which makes it more unlikely the sump side will lose its prime. The money invested in it when doing any upgrades or even if it is your only upgrade is well spent in my opinion. 
     
    On the TwinCam they managed to counter this by making the sump pickup longer and smaller which also helped counter the variances in crankcase pressure caused by the pistons going up and down. The M8 just has a big hole on the right casewhere the oil pump connects. Harley has tried making the oil pump pickup smaller, whether that is working I can't say. Also, that's why if you idle it on the side stand there may be some extra oil collect in the sump. The S&S won't keep that from happening, but it should clear it soon after you stand the bike up straight. 
      
     

  • DocGreen
    DocGreen
    6 years ago
    Quoting mickle on 05 Aug 2018 12:09 PM

    Something I found informative whilst looking through the American Forums, I am waiting on one of these Pumps to arrive for my CVO.


    Could someone be kind enough to explain the "Dual Scavenger" pick up system on this S&S set up that I her about that make it better than the Fueling set up? It's probably apparent to most, but I'm not so familiar with that aspect of these two pumps. TIA.. 
     
    ....... 
    The stock pump has two scavenging pickups, one for the cam case and one for the sump in the crankcase. It only has one scavenging gerotor which is the pump pulling on both pickups. So if the cam case gets pumped dry the pump will suck air on that side which can cause it to lose prime on the crankcase side which will result in sumping. Try putting two soda straws in your mouth, one shorter than the other. When the liquid gets below the short straw it will be harder or impossible to suck liquid through the other straw as long as you are pulling through both. 
     
    The S&S pump has a gerotor or pump for each pickup which makes it more unlikely the sump side will lose its prime. The money invested in it when doing any upgrades or even if it is your only upgrade is well spent in my opinion. 
     
    On the TwinCam they managed to counter this by making the sump pickup longer and smaller which also helped counter the variances in crankcase pressure caused by the pistons going up and down. The M8 just has a big hole on the right casewhere the oil pump connects. Harley has tried making the oil pump pickup smaller, whether that is working I can't say. Also, that's why if you idle it on the side stand there may be some extra oil collect in the sump. The S&S won't keep that from happening, but it should clear it soon after you stand the bike up straight. 
      
     

    Hey mickle, beautiful bike BTW ;) I suspect the main improvement in both the fueling and the S&S twin gerotor pumps comes down the physical size and tolerances of the units.
    The S&S certainly sounds good and I can appreciate having 2 suction pumps/2 inlets as opposed to 1 suction pump/2 inlets - but there is a regular poster on the US HDforums who has fitted the fueling pump to his built 120 and has repeatedly said he has had absolutely no dramas since install, where it sumped using the original style pump.
    Can't even remember what revision pump HD are up to - 8 I think? I read S&S have revised their pumps once also - don't know what for though.
    Certainly watching to see how this whole shemozzle turns out.

    DocGreen

  • Hoodeng
    Hoodeng
    6 years ago
    The OEM pump is internally bridged or to describe it another way ,the scavenge section has two timed sectors to it created by a cast section dividing the scavenge section into two chambers,the first scavenges the gear case, the second the bottom end ,this method of scavenge has proved effective since first used on the 26204-91A  type Sportster pump,this system was also used on the Twin cam.The reason this system was devised was to minimize the amount of oil that was churning in the crankcase section .
    As for the pump loosing prime if it sucks air , this is not the case, if the gerotors are wet with oil it will keep prime,in the example of sucking on two straws ,one shorter than the other, imagine sucking on one and then going to the other separately ,this is effectively what is happening in the pump. The return oil is always aerated as the return side of the pump is always a greater capacity than the feed side whether it be single stage or two stage.

    Twenty plus years ago Zippers manufactured the Pro Flow pump for Sportster's that had a dual scavenge single feed system ,i used one on a engine i built for myself many years ago , i sometimes feel we fix a problem that did not really exist ,but could have been of use with benefit in some circumstances.

    The sumping issue with the M8 looks to be very limited to a specifically modified model,yet its broadcasting of fault makes a lot of guys think they are sitting on some kind of pending failure ,time will tell ,Harley have a good reputation for fixing faults in products that have only shown up after extended use or a history of less than predicted performance.

  • Krash Kinkade
    Krash Kinkade
    6 years ago
    well put!
    in the day's before mobile phones & internet, no one knew, so did not worry. unless they saw oil come out the crank breather.
  • mickle
    mickle
    6 years ago
    I for one don't want to be sitting on the side of the road 1000kms from home waiting for Harley assist (been there done that) my plans for my new CVO were always
    going to be a stage 4 or better build, now apparently these builds have a chance albeit small of sumping, anyone thinking of this type of modification would be mad not
    to install an aftermarket pump, especially if you can maintain your warranty like I will.
  • DocGreen
    DocGreen
    6 years ago
    Quoting mickle on 06 Aug 2018 03:34 AM

    I for one don't want to be sitting on the side of the road 1000kms from home waiting for Harley assist (been there done that) my plans for my new CVO were always
    going to be a stage 4 or better build, now apparently these builds have a chance albeit small of sumping, anyone thinking of this type of modification would be mad not
    to install an aftermarket pump, especially if you can maintain your warranty like I will.

    The problem isn't  contained to modified 114's, it has affected stock 107's according to US HDForums.
    Good description Hoody, thanks.
    Mickle, not sure how you'd keep your factory drive train warranty mate, is the dealer backing it? 
    Haven't decided if I'll modify the motor past stage 1, but if I do I'll be seriously considering the S&S set up also.
  • mickle
    mickle
    6 years ago
    Quoting mickle on 06 Aug 2018 03:34 AM

    I for one don't want to be sitting on the side of the road 1000kms from home waiting for Harley assist (been there done that) my plans for my new CVO were always
    going to be a stage 4 or better build, now apparently these builds have a chance albeit small of sumping, anyone thinking of this type of modification would be mad not
    to install an aftermarket pump, especially if you can maintain your warranty like I will.

    Quoting DocGreen on 06 Aug 2018 05:25 AM

    The problem isn't  contained to modified 114's, it has affected stock 107's according to US HDForums.

    Good description Hoody, thanks.
    Mickle, not sure how you'd keep your factory drive train warranty mate, is the dealer backing it? 
    Haven't decided if I'll modify the motor past stage 1, but if I do I'll be seriously considering the S&S set up also.

    The dealership has already put in writing the full warranty of my build including Woods cams and all the S&S good bits, this was done on a once only
    goodwill gesture because of the stuff up that I had in receiving this bike, nearly 10 month wait. If this build fails the dealer principle himself will foot
    the bill, not that I am expecting to use the warranty. I didn't have a complete win in this build, my initial request was 124ci, oh well maybe in 24 months.
  • DocGreen
    DocGreen
    6 years ago
    Quoting mickle on 06 Aug 2018 03:34 AM

    I for one don't want to be sitting on the side of the road 1000kms from home waiting for Harley assist (been there done that) my plans for my new CVO were always
    going to be a stage 4 or better build, now apparently these builds have a chance albeit small of sumping, anyone thinking of this type of modification would be mad not
    to install an aftermarket pump, especially if you can maintain your warranty like I will.

    Quoting DocGreen on 06 Aug 2018 05:25 AM

    The problem isn't  contained to modified 114's, it has affected stock 107's according to US HDForums.

    Good description Hoody, thanks.
    Mickle, not sure how you'd keep your factory drive train warranty mate, is the dealer backing it? 
    Haven't decided if I'll modify the motor past stage 1, but if I do I'll be seriously considering the S&S set up also.

    Quoting mickle on 06 Aug 2018 06:02 AMedited: 06 Aug 2018 07:36 AM

    The dealership has already put in writing the full warranty of my build including Woods cams and all the S&S good bits, this was done on a once only
    goodwill gesture because of the stuff up that I had in receiving this bike, nearly 10 month wait. If this build fails the dealer principle himself will foot
    the bill, not that I am expecting to use the warranty. I didn't have a complete win in this build, my initial request was 124ci, oh well maybe in 24 months.

    well done on what you will be getting covered anyway mickle, pretty decent dealer obviously. Certainly some good results with these new engines.
    Keep us posted when you do the work please mate.
    DocGreen
  • mickle
    mickle
    5 years ago
    Quoting DocGreen on 06 Aug 2018 05:25 AM

    The problem isn't  contained to modified 114's, it has affected stock 107's according to US HDForums.

    Good description Hoody, thanks.
    Mickle, not sure how you'd keep your factory drive train warranty mate, is the dealer backing it? 
    Haven't decided if I'll modify the motor past stage 1, but if I do I'll be seriously considering the S&S set up also.

    Quoting mickle on 06 Aug 2018 06:02 AMedited: 06 Aug 2018 07:36 AM

    The dealership has already put in writing the full warranty of my build including Woods cams and all the S&S good bits, this was done on a once only
    goodwill gesture because of the stuff up that I had in receiving this bike, nearly 10 month wait. If this build fails the dealer principle himself will foot
    the bill, not that I am expecting to use the warranty. I didn't have a complete win in this build, my initial request was 124ci, oh well maybe in 24 months.

    Quoting DocGreen on 06 Aug 2018 09:25 AM

    well done on what you will be getting covered anyway mickle, pretty decent dealer obviously. Certainly some good results with these new engines.
    Keep us posted when you do the work please mate.
    DocGreen

    I have done close to 5,000 kms on the build now and have had the final Dyno tune performed 2 weeks ago (Maztech), 132.4 HP, 138.1 TQ, the cam
    loves being around 3,000 - 4,000 (Woods WM8-4860, 600 lift) and has around 130TQ at 2,800. Not so much worried about the numbers but you can
    certainly feel the power and good idea to have the back rest on to stop from getting bucked off. The plan in 18months for this build is to go to 128ci
    only requiring pistons and cylinders.
  • Nutty
    Nutty
    5 years ago
    Quoting Hoodeng on 06 Aug 2018 12:20 AM

    The OEM pump is internally bridged or to describe it another way ,the scavenge section has two timed sectors to it created by a cast section dividing the scavenge section into two chambers,the first scavenges the gear case, the second the bottom end ,this method of scavenge has proved effective since first used on the 26204-91A  type Sportster pump,this system was also used on the Twin cam.The reason this system was devised was to minimize the amount of oil that was churning in the crankcase section .
    As for the pump loosing prime if it sucks air , this is not the case, if the gerotors are wet with oil it will keep prime,in the example of sucking on two straws ,one shorter than the other, imagine sucking on one and then going to the other separately ,this is effectively what is happening in the pump. The return oil is always aerated as the return side of the pump is always a greater capacity than the feed side whether it be single stage or two stage.

    Twenty plus years ago Zippers manufactured the Pro Flow pump for Sportster's that had a dual scavenge single feed system ,i used one on a engine i built for myself many years ago , i sometimes feel we fix a problem that did not really exist ,but could have been of use with benefit in some circumstances.

    The sumping issue with the M8 looks to be very limited to a specifically modified model,yet its broadcasting of fault makes a lot of guys think they are sitting on some kind of pending failure ,time will tell ,Harley have a good reputation for fixing faults in products that have only shown up after extended use or a history of less than predicted performance.

    Re; the S&S twin scavenge system. The design brief wasn't about trying to stop the scavenge rotor losing prime, as Hoodie says, that wont happen.

    The issue as S&S (and a few other tribologists involved in sorting the sumping issues) see it, is isolating the pressure differentials of the two scavenge systems (crankcase and camchest) The MoCo came out with a bearing seal to attempt to isolate pressure conditions in the two scavenge voids (whilst leaving them looped at the scavenge rotor in-port...). The S&S pump mechanically separates the scavenging into two scavenging systems in-bye so their ports are completely separate.

    Bigger builds of the M8 with larger bores create greater pressure differentials as the big slugs do their thing. It's no coincidence that the issue is more serious for big bore and high rpm engines. It'll be interesting to see if the S&S has a 100% success rate, engineering-wise it makes sense.

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