Excessive Engine Pressure
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1st Gear
Joined: May 2014
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From: Belleville il
Excessive Engine Pressure
I have a 1993 HD FXR with breathable heads. Recently, I rebuilt the motor and bored cylinders out to .020 and installed Wiseco 10:1 pistons. Also, installed S&S breather, Harley tappets, Harley tappet guides, and Harley push rod covers.
Currently, having problems with oil leaking through lower push rod covers. I suspect that motor is creating to much pressure.
On the 1993 engine case, is there vent plug that I can remove to install a hose fitting to help relieve pressure?
I own a Harley shop manual for that year/model, but I cannot find any mention of a vent plug?
Hoping for an easy fix!
Thanks
Currently, having problems with oil leaking through lower push rod covers. I suspect that motor is creating to much pressure.
On the 1993 engine case, is there vent plug that I can remove to install a hose fitting to help relieve pressure?
I own a Harley shop manual for that year/model, but I cannot find any mention of a vent plug?
Hoping for an easy fix!
Thanks
Seasoned HDF Member
Joined: Nov 2006
Posts: 12,878
Likes: 5,449
From: la la land jerzey
your rings have not sealed or you have driven it to fast too soon and the cylinder walls are scrached causing the ring seal to go away
i have seen it come back but most times it has to come apart again -
try driving it with engine speed no faster than 2500 for a couple hundred miles
i have seen it come back but most times it has to come apart again -
try driving it with engine speed no faster than 2500 for a couple hundred miles
Road Master
Joined: Feb 2014
Posts: 913
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From: indiana
ive seen this a lot. a small portion are from improper break in. and the biggest problem they didn't wash the cylinders properly after boring. that hone grit will ruin a new cylinder if not cleaned out
Dirt don't hurt
Joined: Jan 2011
Posts: 21,065
Likes: 4,561
From: Haslet Texas
I just went through exactly the same thing. I found oil all down the side of my bike in alarming amounts.
I took it all back apart again and the only thing I could find wrong was that I had the 2 longer bolts in the cam chest backwards.
I have no idea why but it doesn't leak anymore.
I took it all back apart again and the only thing I could find wrong was that I had the 2 longer bolts in the cam chest backwards.
I have no idea why but it doesn't leak anymore.
Seasoned HDF Member
Joined: Jun 2010
Posts: 9,332
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From: Upstate New York
You don't say what you are using for pushrods, but if you are using adjustable or "quick install" pushrods, it is possible to have a pushrod that is "bent" (actually brazed together crooked). As adjustable pushrods are larger diameter than the stock pushrods, it doesn't take much eccentricity for the pushrod to be able to hit the cover. If this happens, as the pushrod rotates during running, it can actually "rock" the pushrod cover enough to break the seal, usually at the lower o-ring. This can cause an intermittent leak.
I know this from experience.
I know this from experience.
Seasoned HDF Member
Joined: Jun 2010
Posts: 9,332
Likes: 3,873
From: Upstate New York
I just went through exactly the same thing. I found oil all down the side of my bike in alarming amounts.
I took it all back apart again and the only thing I could find wrong was that I had the 2 longer bolts in the cam chest backwards.
I have no idea why but it doesn't leak anymore.
I took it all back apart again and the only thing I could find wrong was that I had the 2 longer bolts in the cam chest backwards.
I have no idea why but it doesn't leak anymore.
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1st Gear
Joined: May 2014
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From: Belleville il
With the motor hot and the throttle wide open, I performed a compression test on each cylinders. Both cylinders measured at 140 psi. Afterwards, I poured a small amount of oil in each spark plug hole, and performed another compression test. Each cylinder peaked at about 185 psi. I think I do have leaking piston rings.
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Road Master
Joined: Feb 2014
Posts: 913
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From: indiana
With the motor hot and the throttle wide open, I performed a compression test on each cylinders. Both cylinders measured at 140 psi. Afterwards, I poured a small amount of oil in each spark plug hole, and performed another compression test. Each cylinder peaked at about 185 psi. I think I do have leaking piston rings.
Road Master
Joined: Oct 2011
Posts: 957
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From: Carlsbad Springs Ontario
Dont panic yet !
With the motor hot and the throttle wide open, I performed a compression test on each cylinders. Both cylinders measured at 140 psi. Afterwards, I poured a small amount of oil in each spark plug hole, and performed another compression test. Each cylinder peaked at about 185 psi. I think I do have leaking piston rings.
In my experience the psi. difference you see between hot/normal and hot/wet is ok. for a motor that has not been " correctly " run in yet.
You said you installed a aftermarket " breather ? " and i suggest you check that for proper operation. Also check the pushrod tubes to ensure you have replaced the old o/rings etc. etc.
I suspect that you have a simple oil leak at the pushrod tubes otherwise there would be oil spewing out everywhere.
Relax and let us know what you find .