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[Bagger]

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.

[Bagger]

Some possible solutions?

a.   Ensure the oil tank is not overfilled.  The tank must have air at the top to allow for venting.  No air equals no venting.  No venting means that excess oil will be forced out somewhere, the first place usually being into the air cleaner.
 
b.   Oil pump alignment.  Pump misalignment can result in premature wear, as well as cause an improper seal against the cam support plate and /or crankcase.  On the cam support (feed) side of the pump, an improper seal allows oil seepage into the gear case and creates a possible blow-by problem.  On the crankcase (return) side, an improper seal might result in less than-ideal oil scavenging of the crankcase/flywheel compartment. 

c.   Ensure drain holes in rocker support plate underneath the breather assemblies are drilled cleanly through - not blocked or rough edges.  Drill holes with #43 drill bit.

d.   Ensure correct oil filter is on the engine.

e.   Check for clogged oil return line.  Be sure the return hose to the oil pan isn't kinked, pinched, restricted.  Pull the hose off and run water through them to be sure.. In colder/humid climates, a hardened "plug" of milky oil condensation-sludge can partially block the hose.  Check passages through the tranny case and pan are open & clear.

f.   Check for excessive cylinder/ring leakage.

g.   Warped or wrongly installed parts will allow excess oil to bleed off into the gear case and the excess oil will be forced up the pushrod tubes where it will overwhelm the breather system.  For example – is the cam support plate warped, if so then oil pump O-ring will not seal the two mating parts.  Is the rocker support plate warped?

h.   Replace the rubber umbrella valves in the breather assembly.

i.   Replace breather assembly foam filter. Breather Filter: HD P/N 63815-99

j.   Replace plastic breather assembly that tend to warp with the metal ones (p/n 17650-02) – Stock on 2004 and up. 

k.   Install two gaskets (p/n 17592-99) under the breather baffle to give the oil a tiny bit more room to accumulate while draining down.

l.   Help the additional air escape the engine more efficiently.  The breather bolts that affix the air cleaner to the heads are hollow.  The holes in the bolts are the way the breather system transfers vented air into the air cleaner assembly – Drill out the breather bolts one or two drill sizes.  Making the holes larger will allow more air to pass through in the same amount of time.

m.   Examine all junctures between oil-passing parts and O-rings – ensure correctly installed.  Some crucial areas are:  1. The side of the oil pump that fits against the cam support plate, which is the pump’s feed side. O-ring #11286 seals the pump against the support plate.  2. O-ring #11301 seals the cam support plate to the engine case.  3. On a TC88B engine there’s an extra feed opening for the counter balancing system, which also takes a #11301 O-ring.  If this O-ring is missing, crimped, nicked, etc., oil will bleed past the junction and down into the gear case.  All 2000 and later cam support plates have this feedhole.

n.   When installing the support plate on a rubber-mounted TC88 motor there’s a screw and washer blocking this feedhole since there’s no counter balancer system in this engine.  If this feedhole isn’t blocked, then oil will be fed right into the gear case, the result being oil blow-by and a loss in oil pressure.

o.   Try an S&S Reed Valve. Not compatible with the Feuling Super Oil Pump. Page 40 - 41 of S&S Catalog
http://www.sscycle.com/catalog16/pg/Twin_Cam/html/Twin_Cam.htm

p.   Try Doherty Mystfree Vents
http://www.dohertymachine.com/

q.   Try TP Engineering Pro Vent Rocker Boxes http://www.tpeng.com/rockerbox.html

[Bagger]

http://www.mklsportster.com/xloilblowbyarticle.htm

Routing the Breather Hose Into the Air Cleaner:  Many Harley mechanics defeat one of the primary benefits of the breather kit when they route the breather hose into the air cleaner, on the inside of the air filter itself.  Besides the fact that this defeats the purpose of the breather in the first place, it allows an oily mist into the combustion mix of your engine.  The engine is designed to ignite a mixture of gas and air in the combustion cycle - adding a heavy oil mist to this mixture serves to greatly contribute to excess carbon formation in the combustion chambers, on piston tops and glaze cylinders as the oil burns along with the gas and air.  Obviously, this leads to an eventual decline in the performance and reliability of the motor in the long term through this and other related factors (such as fouled plugs).
So, if you have your breather hose routed into your air cleaner, reroute it to the atmosphere - the EPA may not approve, but your engine will thank you for it.

Do Crankcase Vents work: 
http://www.nightrider.com/biketech/crankvent_test.htm

Nightrider's Motorcycle Performance Guide can not state that the use of any Crank Vent will enhance the performance of an engine although we have strong subjective evidence that the devices are effective in reducing blown rocker box gaskets. We can state that these devices will not hurt performance.

Nallin Racing Head Service did testing for increased power: 


http://www.nrhsperformance.com/tech_breathervalves.shtml

Bottom line here, folks, I tried my damndest, I can't find power with these devices. I know that pisses some people off. All I have to say is "show me". Don't just show me a result, either, anyone can skew procedures or pick and choose among the full range of results to support what he's trying to say. Show me procedures and ranges of results.
Here are some crank vent products:

http://www.cas4.com/engine/engine-crankcase-breathers-breather-valves2.html
http://www.chopperscycle.com/page/VTS/CTGY/41-311
http://www.kuryakyn.com/products.asp?bn=harley&ci=2350
http://www.speedsperformanceplus.com/products.html
http://www.dohertymachine.com/tech_tips_powervent.html
http://www.dohertymachine.com/catalog_TwinKit.html
http://www.dohertymachine.com/catalog_inlinepv.html

[Bagger]

S&S addresses the issue with their “Reed Valve”.  Their marketing hype is on page 40 and 41 of http://www.sscycle.com/catalog16/pg/Twin_Cam/html/Twin_Cam.htm
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 .

TP Engineering has addressed the issue with their engines and Twin Cam models as well as all 1992 and later EVO big twins, and 19991-2003 EVO Sportsters.  You can read about TP’s $900 solution at
http://www.tpeng.com/rockerbox.html

Some pictures of the TP Rocker Boxes in this Hot Bike article: http://www.hotbikeweb.com/tech/0303hb_cam/

TP Engineering has a Pro-Vent rocker box that allegedly cures oil blow-by. TP has supposedly reengineered the way oil is separated from the pressurized air sent to the rocker boxes, as well as how the air flows out of the engine and into the breather system.  Easier air movement separates oil from the air more efficiently and eliminates oil blow-by into the air cleaner, without the use of the rubber flappper valves or foam filters to scrub the oil from the air.  TP uses a series of machined labyrinths in its rocker boxes that collect the oil droplets as the oily pressurized air traverses the passages at high speeds.  The separated oil is then returned to the engine, while the now-clean air is allowed to exit the engine and go into the air cleaner.  As the oily pressurized air is created and forced out of the crankcase, it is blown into the gear case, up the pushrod tubes, and into the first chamber of the Pro-Vent rocker box system via three entry holes that begin the process of extracting oil droplets from it.  Each surface touched by the pressurized air collects some of its oil.  The oily pressurized air collides with the walls of the chamber and is forced to make a series of turns before climbing the last wall and flowing through the entry hole into the next chamber.

In the second chamber, the pressurized air also swirls and collides with its walls.  So by the time the air climbs the final wall on its way out of the chamber, it is free of oil and ready to enter the crossover channel in the rocker box cover, which routes the cleaned air out of the head and into the air cleaner.

R&R Cycles
http://www.v-twinforum.com/forums/showthread.php?t=100338&highlight=Support+Plate
http://www.rrcycles.com/store/newrr.html#rrcamplate

The R&R cam plate is vastly differant from all others, it is a camplate/camcover which are both functional and work in conjunction with each other.

Problem 1
When the flywheels shift or have excessive runout the pinion shaft whips causing the camplate to flex and leak oil from its mating surfaces (excessive oil in th case), secondly this excessive runout will cause the oil pump gerotars to bind against the oil pump housing causing some scoring in the oil pump body as Im sure many of you have seen.

Fix 1
The R&R camplate does not mount inside of the camchest instead it is much heavier duty and mounts to the face of the whole camchest making it a much more rigid setup. This reduces the whipping action of the pinion shaft which is turn solves the problem defined above. Secondly the surface between the camplate and camchest in fully gasketed therefore preventing any leaking of oil into the camchest compartment.

Problem 2
Excessive pressure in the case causes oil to stay perched in the heads (oil can't fully gravity return from the heads while case is pressurised i.e. bike is under throttle). This oil gets excessivly hot, and when the bike is dethrottled, this excessively hot oil, when returning to the camchest is easily aireated due to its low viscosity (thiness). Your oil bag oil level will grow from 1/2 to 5/8 inch from cold to hot ladened with this aireated oil . This aireated oil then returns to the engine, since air is compressable the pressure applied to the lifters will compress the air in the oil and then when there is pure hydrology the lifter will start lifting (noisy lifters). The aireated oil does not lubricate engine parts as well either.

Fix 2
The camcover has a oil/air scrapper labyrinth which allows the case to breathe (vent) to atmosphere through a vent on top of the cam cover. This reduces the pressure in the case while under throttle, therefore solving problem 2.

[Bagger]

Oil Down Your Leg? - John Sullivan – Easy Rider Magazine
Easyriders January 2006
Issue 391|
Pgs. 160-161

Product Review

http://www.dohertymachine.com/easyriders2006.php?osCsid=b7aa2cc4d3273efb88157600127953e5
http://www.dohertymachine.com/product_info.php?cPath=1&products_id=99

Harley's Twin Cam 88 is a great motor. In stock from they make half again as much power as the Evo did and there are off-the-shelf kits to build them up to 124 inches. They have only one area of concern, which involves the cylinder head breather system. It seems that some motors pump oil out of the cylinder head breather passages into the air filter or whatever they are connected to. If your motor's breathers are routed to the air filter back plate, you could wind-up with a bit of oil running down your right leg after a long ride.
This is not a new problem. We first saw it back in 1999 and there appears to be more than one reason for it. These include combustion gases leaking past the piston rings, incorrect alignment of the oil pump, poor sealing of the oil system's O-rings, not enough volume of the scavenge side of the oil pump and inadequate oil separation in the breather valve. Not all of these items occur in every motor; in fact we would be surprised to find one motor with all of them.

We think that the two biggest reasons for excessive oil blow-by are incorrect alignment of the oil pump and poor oil separation in the cylinder heads' breather valves. Most of the oil pump alignment problems are caused by inexperienced technicians who are installing camshafts and do not follow the correct oil pump alignment procedure when the reinstall the cam plate. The poor oil separation up in the cylinder heads is caused by the stock breather valves being overwhelmed by the volume of oily/air mist that gets up to the valves during a really hard ride.

Tim Doherty of Doherty Machine has spend the past several years working on the oil separation problem in the cylinder heads and he's come up with a new breather valve design. After looking at his design, he is either very smart or an ex-farmer. His Mystfree valve uses a two-chamber oil separator, whereas the factory breather valves have a single chamber separator that is fitted with a gauze element.
In the Mystfree design the first, or stock oil separation chamber, which is cast into the center of the rocker arm support, is augmented by a cylinder that protrudes into it from the bottom of the Mystree valve body. This cylinder has three openings spaced around its edge that cause the pressurized air- oil mist that is inside of the motor to change direction several times as it is pushed towards the exit in the breather valve.

As this mist moves up against the walls of the cylinder, a good deal of its oil content is stripped off and returned via the stock bleed holes in the bottom of the chamber. It's kind-of like when the wind pushes damp air through plants and their leaves catch the dew.

When the pressurized air passes through the six holes in the Mystfree valve, it hits the bottom of the neoprene valve cause it to rise up forming a second chamber. At this point any oil remaining in the air is removed by the aluminum valve seat and drains back through the lower chamber and into the rocker box.

The neoprene valve that Tim uses is of a smaller diameter than that of the stock umbrella valve, it therefore develops a higher vacuum in the second separation chamber, which helps to pull any oil back into the cylinder head's rocker box. The idea behind the Mystfree valve is sound and his machining is flawless.

Having seen how well the Mystfree valve worked in a 95-inch motor, we decided to use them in a high performance 103-incher we are building. The Doherty Mystfree breather valves are installed in the same manner as the stock breather valves and come with all needed gaskets and mounting bolts.
- John Sullivan
Easyriders

 
IMPORTANT SUPPLEMENTAL INSTRUCTIONS
NOTICE FOR ALL
FL MODEL MOTORCYCLES
 
FL Model Motorcycles require a total oil capacity of 4 quarts. Overfill conditions can result in oil carryover even after the installation of the Mystfree units. When oil and filter is changed in an FL Model the recommended refill capacity is 3.5 quarts NOT 4 quarts since approximately ½ quart remains in the engines sump and gear case during an oil change.
 
DRILLING ROCKER ARM STANDS (OPTIONAL ALL MODELS)
Included in your Mystfree kit is a number 43 drill bit, which measures .089 in diameter. There are two oil drain return holes located in the rocker arm stand cavity in which the Mystfree mounts. 

We have found that the oil return holes in the rocker arm stand are too small to adequately return standing oil. If you are experiencing a high volume of oil carryover exiting the breather system; we recommend the following modifications: These two holes presently measure .060 in diameter. In Twincam 88 style engines, that are moving above normal amounts of oil to the rocker box area, it is recommended that these holes be enlarged to .089. This is easily accomplished by removing the rocker arm assemblies and enlarging the holes with a common electric or portable drill with the drill bit that has been provided in your kit. If you need further technical assistance, please contact Doherty Machine at 928-541-7744.

[Hoist!]

My solution. Doherty Power Pacc and run the breather tubes to the ground, instead of the backplate of the air cleaner. Just like the good old days when the crancases themselves were vented to the ground. This complicated breather system is another result of EPA laws and not better engine designs. You'll never see a drag racing engine that's not directly venting the crancase. And they're venting to the atmosphere! HD did the same for years. My '85 has a crankcase vent tube run from the case to the bottom of the frame. I bought S&S cases for my Pro Street that are "old style" cases with the same type of crancase venting. I'm now running the DPP vents from the heads to the ground. I don't need that chit filthying up my air cleaner so I can burn that oil instead of venting it. And most of it just drips out of the backplate anyway and spews everywhere as you're riding. We can't change this engine design without replacing these engines. But we don't have to vent the breathers into the air cleaner either. Hoist!

[SOKOOLJ]

BAGGER,

Looks like somebody did my home work again. LOL. Thanks for the info.

SOKOOL

[djkak]

My solution. Doherty Power Pacc and run the breather tubes to the ground, instead of the backplate of the air cleaner. Just like the good old days when the crancases themselves were vented to the ground.....HD did the same for years. My '85 has a crankcase vent tube run from the case to the bottom of the frame. I bought S&S cases for my Pro Street that are "old style" cases with the same type of crancase venting.......Hoist!

Not that it matters one way or the other but H-D crankcases have been vented to the air cleaner since Jan 1, 1978; the beginning of the "Ham Can" era. To be more specific, 1978 Big Twins with a sequential VIN >= 60,000 are emission units equipped with the Prestolite electronic ignition and vented Ham Can air cleaner. Previous to this the crankcase vent, supplemented with oil from the return pump was used to lubricate the rear drive chain.

djkak

[Hoist!]

Not that it matters one way or the other but H-D crankcases have been vented to the air cleaner since Jan 1, 1978; the beginning of the "Ham Can" era. To be more specific, 1978 Big Twins with a sequential VIN >= 60,000 are emission units equipped with the Prestolite electronic ignition and vented Ham Can air cleaner. Previous to this the crankcase vent, supplemented with oil from the return pump was used to lubricate the rear drive chain.

djkak

Yeah dj, and we've been diconnecting them from the A/C since then too. My '85 breathes thru the case. There are no breathers from the heads. They vented the crankcase into the air cleaner, which we simply relocated to the atmosphere. I'd rather drip on the floor than destroy my air cleaner and spew all over the bike. Hoist!

[Bagger]

My engine spits oil.  I've tried Doherty Powerpacc, Doherty Myst Free Vents, TP Engineering Pro Vent Rocker Covers, aligned the oil pump several times, ensured all pump mating surfaces and O rings were good and have used a Delkron rocker arm support plate with cleanly drilled drain holes - the engine still continues to spit oil.  Solution now is I accept it due to increased crankcase pressures and I route the breather bolts to the atmosphere.  

2002 FLHRI - 98 ci
(9.48:1 CR) (9.02:1 Corrected CR) (198 psi F/R Cyl.)
Revolution Performance 98" Cylinders
CP Flat Top Pistons
Baisley Super Stock Heads (84cc)
0.040" Head Gasket
TP Engineering Pro-Vent Rocker Boxes
SE Roller Rockers
JM20 gear drive cam
Horsepower Inc 48mm TB
Doherty PowerPacc w/Ness Big Sucker Stage II Filter
Doherty PowerVents
RB Racing LSR 2-1
3.37 final gear ratio
Dyno Jet PCIII USB

[Hoist!]

You know, I just realized your name was Bagger. Welcome to the site man! We have a member, formally known as Bagger, who now goes by REGGAB. I never realized it wasn't him. No wonder you asked who Chuck was. Then I called you Henry. Sorry! Nice engine package you got. Must go nice. Enjoy the site! Hoist!

[bisounours]

Good morning (New) Bagger,

I send you the  from FRANCE.

Thanks for the informations.

It'll be nice for the other members if you present you in the thread "New Member Introduction"
with a pic of your bike 

Best regards

  Jacques

[EAGLE1]

Do Crankcase Vents work: 
http://www.nightrider.com/biketech/crankvent_test.htm

Nightrider's Motorcycle Performance Guide can not state that the use of any Crank Vent will enhance the performance of an engine although we have strong subjective evidence that the devices are effective in reducing blown rocker box gaskets. We can state that these devices will not hurt performance.

I just read the info here and found it very informative, but have found myself in sensory overload with all the differnet products and options, I recently had to have the rear blown rocker box gasket replaced and have surmised it was due to a hard ride back from chi-town at 90+ for a good hour. I have never had oil spitting out of the breather, except when the oil was over filled, but i don't want to worry about the rocker box gaskets every time I run her hard on the 4-laner. these ET krank vent only vent the crank case and block off the head breathers,  while the Doherty Machine Mystfree breather valves vent the heads to the A/C or  to atmosphere     I'm really not sure what would be the best solution for my problem, any suggestions would be appreciated.

[HWYMAN1]

My solution. Doherty Power Pacc and run the breather tubes to the ground, instead of the backplate of the air cleaner. Just like the good old days when the crancases themselves were vented to the ground. This complicated breather system is another result of EPA laws and not better engine designs. You'll never see a drag racing engine that's not directly venting the crancase. And they're venting to the atmosphere! HD did the same for years. My '85 has a crankcase vent tube run from the case to the bottom of the frame. I bought S&S cases for my Pro Street that are "old style" cases with the same type of crancase venting. I'm now running the DPP vents from the heads to the ground. I don't need that chit filthying up my air cleaner so I can burn that oil instead of venting it. And most of it just drips out of the backplate anyway and spews everywhere as you're riding. We can't change this engine design without replacing these engines. But we don't have to vent the breathers into the air cleaner either. Hoist!

Howie,
Okay I will be the stupid one and ask, what kind of tubing from the breather bolts, how long, and exactly where do you vent to ? Any pix? thanks john

[GMR-PERFORMANCE]

Very good tips in this post. WE do all of the mods to the engines when they are for misting. One thing I do not like is the S&S reed valves. I have several here that i would be happy to send to some one if they want to try them. But what we have found is they will sump the engine due to the reed being too stiff. We have pulled them from the 124 crate engines and have sen 5-6 hp as a increase and puking is gone. But then a 124 S&S is a different animal then a normal t/c with there pump and cam plate, cam cover.