The Sportster and Buell Motorcycle Forum - The XLFORUM®

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-   -   Sportster Crankcase Pressure / Engine Breathing / Wetsumping and Mods (

Hippysmack 9th August 2019 03:51

I just got my fuel inlet changed yesterday and my seal in today.
I'll check mine tomorrow but it looks to be the same size as the newer hex side,
Mine should be the same size through though.

Hippysmack 9th August 2019 04:08

Sit Sumping

Originally Posted by dieselvette (Post 5768657)
I am going to fill the oil tank to 1/2 on the dipstick, before connecting the vent line to the cam chest, and make sure no oil comes out of it. Then I can also watch for drainage through the new oil pump while I'm working on the other stuff.

While you're at it, inspect your check ball.
The check ball may have rings formed on it at the seat position by the seating action itself over time.
If the ball doesn't fall back on the ringed area every time the engine shuts down, oil will leak into the groove and then the engine.
A check ball that is no longer perfectly round will not sit properly on the round seat and oil will leak past it into the engine.
This is the older check ball but the ring seat problem can be the same.

I took pics when I removed mine but they don't show the affected area well.
I tested this one with the 86-90 removable filter pad.
I blew in the inlet and moved the ball in several positions until I I could get the air to stop.
When this ring is worn into the ball, there is only one position the ball can land on the seat to stop oil flow from the tank/pump.
That's with the worn in ring going back centered in the seat.

I blew into my feed line with the pump off with the same result as I got with the 86-90 check ball test.
Then I tried it with the filter installed with the same result.
So mine wet sumps because of that while sitting still.

This is good a time as any to include 'sit sumping'.
Someone named it this, may have been DD, but I like it.

Known causes of wet sumping during engine down time:
This is simply oil from the tank draining slowly back down into the crankcase while the bike is parked for any length of time. 1)
When you start the engine, the excess oil in the crankcase is fired out the breather, onto the floor, (or into your air-filter on post-79 models).

Oil Pump:
Worn / damaged oil pump scavenge gears or gerotors (respectively).
The oil pump can't return as much oil to the oil tank as it is receiving from the feed side of the pump.

Damaged teeth or broken gear keys can stop the movement of the teeth thus stopping the scavenge side from working.
It's entirely possible for the feed side to work with the scavenge side not working.
(but that won't last long without something detrimental happening)

Worn / damaged seals (or plates respectively) between the scavenge and feed side of the oil pump.
Gravity pressure is always present on the feed side of the pump.
If the seal between the feed and scavenge side is compromised, that gravity oil will seep past the scavenge side and into the engine.

Check Ball / Check Valve:
All Sportsters have some sort of an oil check system in place.
The check ball can be thought of as the on / off valve for oil supply into the engine.
On 57-85 engines, the check is in the oil pump and on 86 and up engines, the check is in the oil filter pad.
The main objective of the oil check is to close the oil passage during engine shutdown to stop a wet sump condition.
Occasionally the check gets weak or damaged and allows oil to bypass it during shut down.
This will cause wet sumping.
The 57-76 check ball seat in the oil pump body can get dirty and / or pitted from usage and debris.
The spring (whether check ball or valve) can break or weaken which won't push the unit against the seat properly.
Without adequate seat pressure, oil will bypass into the engine.

The check valve is spring loaded. Debris can lodge in the spring seat and keep it open.
The spring can also get weak with wear and the cup seat may not sit properly to seal off.
A small particle of debris may be lodged at the seat position of the check valve/ball keeping the passage open also.



Is your Engine Sit Sumping?

Common red flags include:
Oil puking out the breather(s) on startup:
Oil puking out of the breather tube (pre 91 engines) or the air cleaner (post 91 engines).
Over extended storage periods (winter or down for repairs), oil from the tank drains slowly down into the crankcase.
When you start the engine, the excess oil in the crankcase can be fired out the breather vent(s) and onto the bike / floor.
Lower oil level in the oil tank over various periods of down time.
The amount of oil (when parked) was correct.
Upon later inspection, the tank may be 1-2 quarts low on the stick.
NEVER check the oil level without first running the engine up to operating temp.
This allows the oil pump to return most of the oil in the sump back to the oil tank before checking the level.
Overfilling the oil tank can increase wet sumping:
If you fill the tank (improperly), this will result in too much oil in the engine.
It can also result in oil blowing out the oil tank cap or breather(s).
A sudden loss of power while riding, I think we've covered that.

rocketmangb 9th August 2019 04:50

Those parts are replaced when I do major engine work !
Clean any debris out of the pressure switch hole,it can clog the switch port !

Hippysmack 9th August 2019 05:00


Originally Posted by rocketmangb (Post 5768705)
Clean any debris out of the pressure switch hole,it can clog the switch port !

Good Tip!
I didn't think of that.
Pressure cuts the light off.

Hippysmack 9th August 2019 05:12

I tested a couple switches that I have for operation.


Originally Posted by Hippysmack (Post 5707261)
Testing for an Open Circuit:

These were bench tested but can simulate conditions while installed with the signal wire removed.
This requires a multi-meter set for continuity with the buzzer.
The black probe below can alternately be placed against the engine.
With the engine shut off and the signal wire dis-connected, the contact points should be pressing against each other ensuring continuity.

Touch the probes on the same side of the switch to ensure you have
good contact points on the probes. Clean the area if needed.

Probe each side of the switch and the buzzer on the meter should
sound off thus ensuring continuity between the contacts. If not, the
switch is defective and has to be replaced.

This tested out to be defective with an open circuit.

Testing for the Opening / Closing Pressure:

This setup was made using regular plumbing and air hose fittings.
This requires a multi-meter set for continuity with the buzzer.

The valve was placed inline in case something went wrong

With zero pressure applied, the circuit is closed, continuity is achieved
between the probes and the buzzer sounds off.

With 27 PSI applied, continuity is broken and the buzzer is quiet

This switch didn't make contact until the pressure got down to about 2-1/2 PSI.
However, this test should have been performed with a lower range gauge for tighter low end calibration.

rocketmangb 9th August 2019 05:23

Yall are bad muthas !
I now have a Manometer to test the air flow level from the breather system !

Hippysmack 9th August 2019 05:34

Pics and data please. :clap

rocketmangb 9th August 2019 05:38

Coming soon !

harley506d 9th August 2019 08:20

Replaced my breather bolts a while back as the hexagons were getting worn, both old and new were 1/16" at thread end.
So is puking more common to all those who have changed air box to after market and are now using much larger opening banjo bolts?

60Gunner 9th August 2019 08:27

I figured George would jump on board sooner or later.
I don't necessarily have a high oil pressure issue. No more than anyone does at high rpm anyway. Just stating 30 psi would be an ideal pressure to maintain.

I don't remembermwhere in that 130 page thread testing in the tank vent line took place or you could read it for yourself. I have no need or desire to tee into, vent from, or otherwise pay any particular attention to it to even vaguely care enough to look for it tbh.
I would run any manometer off my cam chest fitting, up the down tube and mount it.

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