Compression Leakdown Failure
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Tourer
Joined: Mar 2007
Posts: 368
Likes: 2
From: Salina, KS
Compression Leakdown Failure
I took my 2005 1200 XL C in for the 15,000 service.
Dealer tells me that my bike did not pass a compression leakdown test (rear cylinder loss 30%, front cylinder 10%), and that I need a top end rebuild. At 15,000 miles, that's a real pisser. The dealer suspects that the root cause may be valve stem seal failure on the back cylinder. Apparently the 2005’s were susceptible to this, however a recall was never done, although the Company did issue service bulletins regarding this.
I have seen some information , but I can't recall anyone ever explaining the relationship between failure of the seals and compression loss. The dealer’s explanation was that the failed seals allow oil to leak into the cylinder. The oil burning then carbons up the cylinder/pistons, creating excessive wear on the cylinder walls, and allowing the compression to leak out of the cylinder. The rear spark plug has always been darker than the front, and the last time I checked (just before I took it in to the dealer’s), the plug showed some crusty carbon deposits on one side of the electrode. I have read somewhere that a one sided deposit is one indication of valve stem seal failure. The front plug looks pretty normal, maybe even a tad lean.
The bike does not now nor has it ever used great amounts of oil—about 3/4ths quart per 5,000 miles. As a result,I am somewhat skeptical. The plug condition kind of supports the diagnosis, but the oil use does not. By the way, I have been using Seafoam in every second or third tank since 10,000 miles. That is supposed? to combat carbon buildup. Apparently not in this case.
Has anybody else had experience with this?
Tourer
Joined: Mar 2007
Posts: 486
Likes: 0
From:
RE: Compression Leakdown Failure
So they are telling you the excessive carbon has caused the rings to leak? Most engines that I have seen that have leaky valve guide seals are usually on the tail end of the engines overall life but there have been a few that have the same condition as you are experiencing. Having built several automotive engines I can tell you that if the seal prematurely failed it will suck oil through the valve stem guide and into the intaketrack.Small amounts usually build carbon right onto the valve stem right below the guide and the carbon tracks back into the guide and increases the wear on the guide itself making the valve incorrectly seat.In this case replacement of the seal,the guide, possibly the valveand regrind or relapping the valve cures the problem. The piston, cylinder walls and piston rings are uneffected by thethis situation. Cylinder walls are damaged by worn out compression rings and oil control rings that carbon up from compression ring blow-by.
I would opt to have the dealer only rebuild the rear cylinder head and see how it fares. I bet you would find the leakdown comes back within exceptable limits.
I would opt to have the dealer only rebuild the rear cylinder head and see how it fares. I bet you would find the leakdown comes back within exceptable limits.
Road Master
Joined: Jun 2006
Posts: 933
Likes: 1
From:
RE: Compression Leakdown Failure
I'll bet the service dept sales has dropped off by now and they are trying to "find" work.If it runs good and isn't using oil I say leave it alone.I have a hard time seeing an EVO engine needing that type of repair without noticable oil consumption.
Club Member
Joined: Feb 2007
Posts: 16,320
Likes: 306
From: Boynton Beach, FloriDuh
RE: Compression Leakdown Failure
ORIGINAL: diablo666
I'll bet the service dept sales has dropped off by now and they are trying to "find" work.If it runs good and isn't using oil I say leave it alone.I have a hard time seeing an EVO engine needing that type of repair without noticable oil consumption.
I'll bet the service dept sales has dropped off by now and they are trying to "find" work.If it runs good and isn't using oil I say leave it alone.I have a hard time seeing an EVO engine needing that type of repair without noticable oil consumption.
I don't even see a leak down test listed as part of a normal service check. Unless you complained of a problem, I don't know why they would have done the test to begin with. Giving them the benifit of the doubt, maybe you have a dealer that goes above and beyond.
Road Warrior
Joined: Jun 2005
Posts: 1,334
Likes: 2
RE: Compression Leakdown Failure
If it does turn out to be a real problem and you are just out of warranty, then call Harley corporate and try to get a goodwill repair done.
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Tourer
Joined: Jul 2007
Posts: 401
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From: hollister fl.
RE: Compression Leakdown Failure
how was your bike running when you took it in for the 15000 mile service .did you take it in for a running problem or just 15000 mile service .if the bike was running fine id have to take it out of that shop & get a second opinion!!!!!!!!!!
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Road Captain
Joined: Jul 2007
Posts: 674
Likes: 1
From: FLORIDA
RE: Compression Leakdown Failure
I would most certainly perform my own compression check if it were my machine.....You can purchase a compression gauge for just a few dollars and its a very EASY check to perform......To check and see if your rings are worn or your cylinder walls etc, take a compression reading......And if its LOW, then squirt some oil directly into the cylinder through the spark plug hole [ where you screw the comp gage into ]Then recheck your compression again......If it then checks noticeably higher, there is a good chance your rings are worn......[ although it sounds like your motor ain't burning much oil at all tween oil changes ]....
Getcha a compression gauge and a bike service manual.........You will save yourself ALOT of money over the years....
Getcha a compression gauge and a bike service manual.........You will save yourself ALOT of money over the years....
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