Oil pressure fluctuation

[Kllongbrake]

It's a Twin Cam 124" in a Touring. I've had some....issues this year and I've ended up with a Dan Thayer 3 stage pump and R&R plate. Now the pressure drops under acceleration from 38psi sometimes down to 15psi then pulls back to 38psi. I changed the oil pressure sender as it was weeping anyway and has 60k on it. No change. I've got a 60psi mechanical gauge on it also to verify that it's really happening.
Anybody seen this before or have any ideas? Thanks for your time. 

[Admiral Akbar]

You have an EVO oil pan gasket in your twincam.

[Kllongbrake]

You have an EVO oil pan gasket in your twincam.

No sir.

[smoserx1]

The cam support plate has a bypass valve in it operated by a spring and I wonder if your spring is too weak.  this is what some folks would replace with a Baisley spring.  The oil filter itself also has a bypass valve that opens if there is too much pressure drop across the media (usually dirty media or very cold temps).  I doubt that is the issue but you could put on a different filter and see if it makes any difference.  You are not running an odd viscosity oil are you?

[BVHOG]

It's a Twin Cam 124" in a Touring. I've had some....issues this year and I've ended up with a Dan Thayer 3 stage pump and R&R plate. Now the pressure drops under acceleration from 38psi sometimes down to 15psi then pulls back to 38psi. I changed the oil pressure sender as it was weeping anyway and has 60k on it. No change. I've got a 60psi mechanical gauge on it also to verify that it's really happening.
Anybody seen this before or have any ideas? Thanks for your time.

Any chance it has an Axtel bypass spring in the plate?

[Kllongbrake]

The cam support plate has a bypass valve in it operated by a spring and I wonder if your spring is too weak.  this is what some folks would replace with a Baisley spring.  The oil filter itself also has a bypass valve that opens if there is too much pressure drop across the media (usually dirty media or very cold temps).  I doubt that is the issue but you could put on a different filter and see if it makes any difference.  You are not running an odd viscosity oil are you?

Redline 20-60 oil
Don't know about the spring or bypass. It's just a new R&R plate with 75 miles on it. I don't have a pop off gauge to check the plate. Is it a problem for the pressure to dip?

[Kllongbrake]

It's a Twin Cam 124" in a Touring. I've had some....issues this year and I've ended up with a Dan Thayer 3 stage pump and R&R plate. Now the pressure drops under acceleration from 38psi sometimes down to 15psi then pulls back to 38psi. I changed the oil pressure sender as it was weeping anyway and has 60k on it. No change. I've got a 60psi mechanical gauge on it also to verify that it's really happening.
Anybody seen this before or have any ideas? Thanks for your time.

Any chance it has an Axtel bypass spring in the plate?

If it does it came straight from Thayer like that. I'll call Randy @ Hyperformance Monday and see what he says about the bypass.
Does the axtell bypass cause a dip in pressure?

[Deye76]

Was the oil pan removed, re-installed? If so, the symptoms are like the wrong gasket that akbar referred to.

[Kllongbrake]

Was the oil pan removed, re-installed? If so, the symptoms are like the wrong gasket that akbar referred to.

No it wasn't. It is vented at the fill tube however it has seen an S&S 3 stage and plate and a Screamin eagle orange plate with high flow pump since vented and there wasn't any issues.

[Admiral Akbar]

Was the oil pan removed, re-installed? If so, the symptoms are like the wrong gasket that akbar referred to.

No it wasn't. It is vented at the fill tube however it has seen an S&S 3 stage and plate and a Screamin eagle orange plate with high flow pump since vented and there wasn't any issues.

Sounds like you fixed it til it was broke. Go back to where you where before.

[Nastytls]

Sounds like you've spent a boatload on them.... Why so many different oil pumps? If it was fine before put it back that way as Akbar alluded to.

[les]

I've got a 124" with the S&S plate and pump.  I've got an Arlen Ness oil pressure gauge.  Oil pressure is wacky.  If I'm out riding and pull over, the time it takes to drink down exactly one beer, when I get back on the bike and start it, the pressure is around zero.  It gradually gets it's way back up to around 40.  If I take my time and slowly have two beers, when I start it the pressure is about 20, and again works it's way back up.  If I start it cold, the pressure is immediately at 40.

If I start it cold and then idle warm up normally, when it gets hot for my first run them it's around 35 - 38.  If I ride it, then stop for a while and the engine is still a bit warm, then pressure works it way up past 40 to the 42 and sometimes 45 range.

The oil pumping system is about as precise as a yard stick.  All over the place.

[koko3052]

les...I would say that it's your gauge...would drive me bonkers!

[les]

les...I would say that it's your gauge...would drive me bonkers!

I thought of that.  But I'd say the gauge is not really operating erratic, or I just think it's not.  It used to drive me crazy, but I've learned to just ignore the weird readings and focus on what it's generally trying to tell me.

My current assessment is that the H-D oil pump architecture is somewhat of an imprecise POS.

[PoorUB]

My current assessment is that the H-D oil pump architecture is somewhat of an imprecise POS.

Only the oil pump?

[Y2KRKNG]

It's a Twin Cam 124" in a Touring. I've had some....issues this year and I've ended up with a Dan Thayer 3 stage pump and R&R plate. Now the pressure drops under acceleration from 38psi sometimes down to 15psi then pulls back to 38psi. I changed the oil pressure sender as it was weeping anyway and has 60k on it. No change. I've got a 60psi mechanical gauge on it also to verify that it's really happening.
Anybody seen this before or have any ideas? Thanks for your time.

Does it do the same thing after the oil is up to normal temp?

[Kllongbrake]

Yes it did. But I only tested that once. An unnamed person, who should know something about this, stated that the only time he'd seen this is in drag racing when the oil goes to the back of the pan and starves the pump. That everything else he hears says the pump and plate are working.
I usually run about halfway up the stick. I filled it and rode it to work. Still did it in the morning. On the way home it was hot out and it quit diving but did start lightly bouncing a few PSI and then would intermittently drop to 20-25ish for a few minutes then would come back up to 35 with no change in load.
Just haven't had the chance to put the SE stuff in. Should be able to do it tomorrow and try it this weekend.

[kd]

I'm thinkin it could be a loose oil intake line at a fitting drawing air but I suspect it would drip when the oil was hot and thin.  Does your oil look foamy or creamy with air?  Another thought not mentioned is the bypass spool in the cam plate. It might be hanging up when hot only from a tight fit and expansion. Or even the spring.

[smoserx1]

An unnamed person, who should know something about this, stated that the only time he'd seen this is in drag racing when the oil goes to the back of the pan and starves the pump.

The only way I could imagine that happening on a Harley touring bike is if someone removed the oil pan and fail to install the baffle.  I would still be suspecting the bypass valve in the cam plate, it sounds like it is opening too soon but I am having trouble understanding how it would happen.

[Hossamania]

Does the sound of the motor change at all when it happens?

[capn]

If the gauge is in the fairing could be the pressure sending unit.

[Kllongbrake]

Does the sound of the motor change at all when it happens?

No it doesn't change. No change in performance either. I'm almost done putting the SE stuff in. I'll ride it tomorrow but I'm sure the SE stuff will work fine again.

[Kllongbrake]

If the gauge is in the fairing could be the pressure sending unit.

I've installed a mechanical gauge to verify issue. It's really doing it. I thought the same though and changed the sending first anyway since it was weeping very lightly.

[pwmorris]

Wasn't there a post about someone having issues with the Thayer pump?
I've never run one, and I never speak of something I personally haven't tested or ran.

I had a several psi oil fluctuation (maybe 5-10) before I vented my tank, and eliminated my crossover line. Now, it's rock solid.

How are you venting this 124"?
Tank?
Case?
Heads?
Cam chest?
Rocker boxes?
Nothing? Just leaving stock, like a 60 HP set up?
This issue just happening now on hot summer days, and not before?
Make sure you are getting advice from owners of 124" and bigger on the street. That regularly run their bikes during hot, 90-100 degree summer days? Are running hard (like I just did today as it's 100 degrees in the SF Valley today and came back from a nice couple hour putt in LA Friday traffic on my hi compression 126"),
in stop and go, big traffic, high speeds, low speeds, freeway jams, etc. as a daily driver, not a "Sunday Starbucks and back to the house to cool off bike"? Or a "I take it out in the AM when it's cool, then it's back to the garage before it gets too hot!"
Or, even worse, "I've got several bikes, and my hot rod 124" only goes out once in a while, or when it's nice and cool outside, and no traffic...."


The 124" is a different animal than a stock HD Twin Cam, and thus requires a different approach to your oil system requirements. Just as your clutch, and other areas need different solutions that have nothing to do with stock set ups.
Also, I run Liqui-Moly, and got rid of by Redline for my street bike oil due to heat related thinning/tapping issues. Still run Redline in my trans, and 10 wt in race bike.

[Kllongbrake]

Wasn't there a post about someone having issues with the Thayer pump?
I've never run one, and I never speak of something I personally haven't tested or ran.

I had a several psi oil fluctuation (maybe 5-10) before I vented my tank, and eliminated my crossover line. Now, it's rock solid.

How are you venting this 124"?
Tank?
Case?
Heads?
Cam chest?
Rocker boxes?
Nothing? Just leaving stock, like a 60 HP set up?
This issue just happening now on hot summer days, and not before?
Make sure you are getting advice from owners of 124" and bigger on the street. That regularly run their bikes during hot, 90-100 degree summer days? Are running hard (like I just did today as it's 100 degrees in the SF Valley today and came back from a nice couple hour putt in LA Friday traffic on my hi compression 126"),
in stop and go, big traffic, high speeds, low speeds, freeway jams, etc. as a daily driver, not a "Sunday Starbucks and back to the house to cool off bike"? Or a "I take it out in the AM when it's cool, then it's back to the garage before it gets too hot!"
Or, even worse, "I've got several bikes, and my hot rod 124" only goes out once in a while, or when it's nice and cool outside, and no traffic...."


The 124" is a different animal than a stock HD Twin Cam, and thus requires a different approach to your oil system requirements. Just as your clutch, and other areas need different solutions that have nothing to do with stock set ups.
Also, I run Liqui-Moly, and got rid of by Redline for my street bike oil due to heat related thinning/tapping issues. Still run Redline in my trans, and 10 wt in race bike.

What do you run? Liqui-moly 10-60?
It was doing it cold and hot.
I've put SE plate and "high flow" pump in and it now works as should again. Builds to 40 at operating rpm and doesn't drop one psi.
I'm convinced there's a problem with the plate. Likely the bypass plunger.  I've got drilled heads behind the AC mounts with 90 degree 3/8" fittings and 3/8" hose going over the rear rocker box and venting to the ground. And the oil tank is vented at the fill neck with a -4 AN fittings and hose to the rear fender with a filter and one way valve.
Can feel the head vents working but they don't drip. I don't flog it very often though. Typically keep it under 5K. Run higher speeds on the freeway for extended periods and everything seems to be working.