There are 2 issues that are always talked about w.r.t. the M8s. Transfer and sumping.
Transfer (trans fluid moving into the primary) seems to only happen with hydraulic clutches, so only touring bikes not softails.
Sumping is what the A1 videos are talking about. That has to do with the engine oil, not the transmission.
That softail with all the oil buildup (happens to be a Fatboy like I have) is why me and many others vent the breathers out of the air filter to avoid all the oil (and hot air) going back into the throttle body.
Now the oil cap breather is said to help to avoid sumping.
Thanks for taking the time to explain. I mistook the video as venting the trans case. What you said makes perfect sense, and venting via the crankcase filler, especially as MoneyFor is doing seems an excellent solution.
This was the valve they could offer me, the measurements where in line what I had in my thoughts. I like to keep it all in one part .. in the dipstick. So whenever the line is cut, lost or
pulled of it still have his function. I'm a person that does not like simple solutions, then I would be like so many other people out there
This makes perfect sense. And using a check valve directly from the crankcase is indeed a 'positive crankcase ventilation' (PCV) solution much like the automotive engineers have done for years,
For others following the discussion, most 4 cylinder bikes don't have this issue, as two pistons rise while two pistons fall, off-setting volume displacement into the crankcase, with only blowby needing to be vented. In contrast, Harley's V-engine with the pistons sharing a single crankpin causes rapid pressurization and depressurization of the crankcase, leading to oil puking out the cylinder heads (where Harley traditionally vents the case through each cylinder). Venting at the crankcase seems a good solution, and even better if a small check valve (e.g., PCV valve) is used - leading to partial negative pressure ("vacuum") in the crankcase, with even small power gains to be recovered.
This makes perfect sense. And using a check valve directly from the crankcase is indeed a 'positive crankcase ventilation' (PCV) solution much like the automotive engineers have done for years,
For others following the discussion, most 4 cylinder bikes don't have this issue, as two pistons rise while two pistons fall, off-setting volume displacement into the crankcase, with only blowby needing to be vented. In contrast, Harley's V-engine with the pistons sharing a single crankpin causes rapid pressurization and depressurization of the crankcase, leading to oil puking out the cylinder heads (where Harley traditionally vents the case through each cylinder). Venting at the crankcase seems a good solution, and even better if a small check valve (e.g., PCV valve) is used - leading to partial negative pressure ("vacuum") in the crankcase, with even small power gains to be recovered.
The crankcase and oil tank are already vented through the vents in the cylinder heads. These vents have check valves and work as you describe. I do not believe that adding a third vent will do any good. Bikes that puke oil are either over filled, are sumping a little and churning the oil, or have excessive piston ring blow by. The new 2020 oil pump makes more sense to me to solve these issues.
Originally Posted by BobRRView Post
S&S says it has determined the problem to be the continuous rise and fall of the air pressure in the crankcase, cam chest and rocker boxes. That the pressure changes are caused by large volume of air moving in and out of the crankcase as the pistons travel up and down. As a result of this air flow and the changes in pressure in the cam chest, air also flows in and out of the rocker boxes through the cylinder head oil drain passages. At sustained high speeds the constant in and out flow of air in the rocker boxes interrupts the free flow of oil from the cylinder heads to the cam chest . In fact a small quantity of oil, pushed up and down by the pressure changes, is trapped in the drain passage, effectively blocking the passage so that no oil can drain out of the rocker boxes . When enough oil has accumulated in the rocker boxes, it will start to blow out the breather passage to the air cleaner and ends up all over your bike, your passengers new boots, and in extreme cases on your rear tire .
Reason for Oil Blow By: More air is displaced by the ascending and descending pistons when a 95" and larger kits have been installed, simply because there's bigger pistons moving up and down. Sustained high rpm riding aggravates blow by because more oil is being pumped into the engine since the pump is turning faster. The rocker boxes become overwhelmed with too much oil that it cannot separate the oil from the escaping air. Some stock displacement engines have oil blow-by problems even when ridden moderately, but that is not the norm. Blow-by does not happen immediately because the oil buildup that causes it takes time to occur. That's why blow-by sometimes doesn't occur until after sustained high-speed riding.
From Nov 04 issue of American Iron - Donnie Smith:
The breather system is all about separating gaseous materials from the oil to allow the engine to vent to the atmosphere without puking oil all over its exterior. The engine must vent the pressure built up in the crankcase by the ascending and descending pistons. As the pistons descend in both cylinders, which happens on the power and intake strokes, the air in the flywheel compartment (crankcase), which is below the pistons, is pressurized because there's less space under the pistons for the air to occupy. The thrashing flywheel assembly also produces a fine oil mist that combines with the air in the crankcase. This oily, pressurized air must be allowed to escape, or it will soon blow out the engine's gaskets and seals. This oily, pressurized air is forced (vented) out of the crankcase, through the spaces between the bearings and races of the pinion bearing, and into the gear case compartment. It is then allowed to go up the pushrod tubes and into the rocker boxes. Once in the two rocker boxes, the oily, pressurized air rushes under the rocker arm support plates and into openings that lead to the breather baffle assemblies - there's one in each rocker box.
The first advantage to making the oily pressurized air go up the pushrod tubes is that gravity assists in separating the heavier oil from the lighter pressurized air, but the separation process needs more help than that.
There is a three-stage system in the rocker boxes for venting the displaced air back into the combustion chamber, where any oil residue is burned off to prevent all but a minimum of emissions from escaping to the atmosphere.
The three-stage system consists of an open-cell foam disc, which can be described as an oil filter gauze element. This open-cell foam disc, which is shaped like a 1" long barrel, scrubs oil from the oil air vapor. The disc is very porous and air is easily blown through the foam.
The oil that gets separated from the air flows through two small return holes in the rocker arm support plate to return to the gear case - unless there's too much oil to deal with!! The cleansed air is then fed through an umbrella flapper valve (the 2nd stage), which rises to let the air through. This flapper valves an umbrella-shaped, one-way, rubber valve that lets air out of the engine, but will not allow it to come back in. Once the piston begins to ascend, pressure in the crankcase drops, and the air in the breather compartment reverses direction. When this happens, the flaps of the umbrella valve drop down, sealing the vent hole and blocking the cleansed air from returning. But when overwhelmed will let oil out of the engine along with the air. The cleansed air then follows a tortuous path in the rocker boxes (3rd stage), which allows air to escape, but separates any residual oil from the air. (Tortuous is the term used by engineers to describe a channel that gases find easy to follow, but liquids do not.) After the oil is separated and the gases flow out of the heads, the gasses are sucked back into the carb, or EFI venturi , and into the combustion chamber to be burned.
Let's assume that what S&S says in the prior post is true based on their observation of running engines.
There are four pushrod cover tubes that connect from the cam chest to the rocker boxes in parallel with the drain passage from each head. In order to block the rocker box oil drains with cam chest air pressure, there needs to enough air flow restriction through the pushrod tubes to build a pressure differential and make that happen.
In looking at pictures of adjustable pushrods, I would estimate that they block the cover tube flow area almost twice as much as standard pushrods. When I swap cams this winter, I'm taking out the adjustables and putting stock pushrods back in along with the new 2020 oil pump. Here's a pic of an S&S pushrod kit and an H-D adjustable pushrod.
Let's assume that what S&S says in the prior post is true based on their observation of running engines.
There are four pushrod cover tubes that connect from the cam chest to the rocker boxes in parallel with the drain passage from each head. In order to block the rocker box oil drains with cam chest air pressure, there needs to enough air flow restriction through the pushrod tubes to build a pressure differential and make that happen.
In looking at pictures of adjustable pushrods, I would estimate that they block the cover tube flow area almost twice as much as standard pushrods. When I swap cams this winter, I'm taking out the adjustables and putting stock pushrods back in along with the new 2020 oil pump. Here's a pic of an S&S pushrod kit and an H-D adjustable pushrod.
Not saying anyone is right or wrong here, but I would like to see what FuelMoto has to say, as fuelmoto makes a set of adjustable chromoly pushrods too.
And I wonder how all of these compare to the Screamin Eagle pushrods.
I also noticed there were a ton of products nyxxed from S&S's store front in the recent few months since the 2020 Model year engine came out. I'm really curious as to what's going on.
Trying to do a bit of research on which tappets and pushrods to go with a new cam, and seems that some of the products I've been watching are disappearing.
Adjustable, no one else sees the weak link. Just a product on the market most use for convenience.
With that said, going back to the original thread, what I did to my softail today.
I looked at it wondering what I can do with this beast. All kinds of thoughts, yes. My budget and shop means limits me.
Dayum shame.
Edit: I remember a time push rods come off and I had to push that friggin scoot 2 miles to the girls apt. They had tools, and pulled the scoot into their kitchen.
I layed both of them sometime during the night while fixin the scoot.
Was no adjustable push rods back then. I still amazed this day, I knew wtf I was doin.
Last edited by Tampa Fatboy; 12-18-2019 at 06:38 PM.
Originally Posted by BobRRView Post
S&S says it has determined the problem to be the continuous rise and fall of the air pressure in the crankcase, cam chest and rocker boxes. That the pressure changes are caused by large volume of air moving in and out of the crankcase as the pistons travel up and down. As a result of this air flow and the changes in pressure in the cam chest, air also flows in and out of the rocker boxes through the cylinder head oil drain passages. At sustained high speeds the constant in and out flow of air in the rocker boxes interrupts the free flow of oil from the cylinder heads to the cam chest . In fact a small quantity of oil, pushed up and down by the pressure changes, is trapped in the drain passage, effectively blocking the passage so that no oil can drain out of the rocker boxes . When enough oil has accumulated in the rocker boxes, it will start to blow out the breather passage to the air cleaner and ends up all over your bike, your passengers new boots, and in extreme cases on your rear tire .
Reason for Oil Blow By: More air is displaced by the ascending and descending pistons when a 95" and larger kits have been installed, simply because there's bigger pistons moving up and down. Sustained high rpm riding aggravates blow by because more oil is being pumped into the engine since the pump is turning faster. The rocker boxes become overwhelmed with too much oil that it cannot separate the oil from the escaping air. Some stock displacement engines have oil blow-by problems even when ridden moderately, but that is not the norm. Blow-by does not happen immediately because the oil buildup that causes it takes time to occur. That's why blow-by sometimes doesn't occur until after sustained high-speed riding.
From Nov 04 issue of American Iron - Donnie Smith:
The breather system is all about separating gaseous materials from the oil to allow the engine to vent to the atmosphere without puking oil all over its exterior. The engine must vent the pressure built up in the crankcase by the ascending and descending pistons. As the pistons descend in both cylinders, which happens on the power and intake strokes, the air in the flywheel compartment (crankcase), which is below the pistons, is pressurized because there's less space under the pistons for the air to occupy. The thrashing flywheel assembly also produces a fine oil mist that combines with the air in the crankcase. This oily, pressurized air must be allowed to escape, or it will soon blow out the engine's gaskets and seals. This oily, pressurized air is forced (vented) out of the crankcase, through the spaces between the bearings and races of the pinion bearing, and into the gear case compartment. It is then allowed to go up the pushrod tubes and into the rocker boxes. Once in the two rocker boxes, the oily, pressurized air rushes under the rocker arm support plates and into openings that lead to the breather baffle assemblies - there's one in each rocker box.
The first advantage to making the oily pressurized air go up the pushrod tubes is that gravity assists in separating the heavier oil from the lighter pressurized air, but the separation process needs more help than that.
There is a three-stage system in the rocker boxes for venting the displaced air back into the combustion chamber, where any oil residue is burned off to prevent all but a minimum of emissions from escaping to the atmosphere.
The three-stage system consists of an open-cell foam disc, which can be described as an oil filter gauze element. This open-cell foam disc, which is shaped like a 1" long barrel, scrubs oil from the oil air vapor. The disc is very porous and air is easily blown through the foam.
The oil that gets separated from the air flows through two small return holes in the rocker arm support plate to return to the gear case - unless there's too much oil to deal with!! The cleansed air is then fed through an umbrella flapper valve (the 2nd stage), which rises to let the air through. This flapper valves an umbrella-shaped, one-way, rubber valve that lets air out of the engine, but will not allow it to come back in. Once the piston begins to ascend, pressure in the crankcase drops, and the air in the breather compartment reverses direction. When this happens, the flaps of the umbrella valve drop down, sealing the vent hole and blocking the cleansed air from returning. But when overwhelmed will let oil out of the engine along with the air. The cleansed air then follows a tortuous path in the rocker boxes (3rd stage), which allows air to escape, but separates any residual oil from the air. (Tortuous is the term used by engineers to describe a channel that gases find easy to follow, but liquids do not.) After the oil is separated and the gases flow out of the heads, the gasses are sucked back into the carb, or EFI venturi , and into the combustion chamber to be burned.
Maybe 15 years ago this was true, but even everyone's favorite backyard engineer, DK Custom Products, showed that the blow-by on the M8 was highest at idle. If an M8 is puking oil, it is either overfull, or has insufficient ring seal, or maybe both. Unless you are at a wide throttle opening, there is vacuum being generated even at high highway speeds. This is true for all naturally aspirated gas-powered engines. The Harley engine is not unique.
If the engine is operating like it was designed, and you have maintained it according to the manual, there should be little or no issues with blow-by, and there is certainly no reason to bolt on a $20 hardware store "fix" onto something that was not broken. I have bought 2 M8 bikes now, and had no problem with blow-by on either of them, and the last bike I bought was over-filled by the factory by almost a quart.
Sumping is of course a different issue. Seems the softails (based on my readings) seem to suffer with it less than touring bikes. The softail has a different oil pan design, and has an additional passage for return over the touring. Not sure if that's actually it or not, but it could be a contributing factor. If the oil cannot drain, and the crank scraper is not designed with tight tolerances, you can get the "oil tornado". This is one of the things that can suck power from any engine where crankcase oil is allowed to touch the spinning crankshaft. It will act like gravity and basically draw oil from the pan and spin around the crankshaft. Maybe the M8 crankcase channel design allows for this in the touring models (or maybe an over-filled softail) but not the softail due to the 1 additional oil drain passage. I'm assuming Harley is trying all the different oil pumps in an attempt to avoid tearing down motors to install crank scrapers. Who knows. It all seems like luck of the draw, which leads me to believe it may actually be a sump gasket sealing issue.
Great discussion and information here, but this thread has officially jumped the rails and with the current discussion it seems like it could use its own thread.
12-17-2019, 09:44 PM
When I swap cams this winter, I'm taking out the adjustables and putting stock pushrods back in along with the new 2020 oil pump. Here's a pic of an S&S pushrod kit and an H-D adjustable pushrod.
