Compression
HDF Community Team
Joined: Jun 2006
Posts: 12,774
Likes: 2,606
From: san antonio
I was looking for any reason other then misting or blow by that would cause oil consumption. I use about a ounce and a half every 100 miles. Not huge but not right either. I suppose its being sucked in through the vent tubes. with about 6500 miles on the bike it was perplexing. When I romp on it a little, I use oil faster. The same story as all the others with the same issue. Thanks again guys! Mike.
Run the leakdown test again; use a true leak down tester. Make sure the piston is a TDC and the engine locked so the crank cannot rotate. Start at 40# and increase the cylinder pressure in 10# increments to 90# taking readings at every 10# increment. Sometimes cylinders will show low leakdown at 40# or 50# but the leakdown will increase with cylinder pressure. You may have done this already but I would want to verify that the 1% leakdown is an accurate measurement.
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Cruiser
Joined: Sep 2007
Posts: 101
Likes: 0
The plugs look as though they are ok, burning a pale gray. All the testing was done at the dealer so I cant tell you the process, only the numbers. I have a stage one with the SE backer plate and a K&N filter with V&H slipons and Techlusion. The bike runs real smooth and has plenty of power, It is just this oil loss thing. The breathers is my guess because of the carbon. You sound like a Harley tech yourself. Thanks for answering.
Cruiser
Joined: Apr 2009
Posts: 137
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From: Dania Beach, FL
Plugs being pale gray is good. Oil would darken them and would residue on the bottom of the threaded-in part of the plug. Harder to see if you use black plugs. This is why I like NGKs, the bottoms are silver and easy to read. I'd lean toward ventilation.
Road Master
Joined: Jun 2008
Posts: 868
Likes: 1
From: Trenton,N.J.
I just had a compression check done on my 2010 Dyna SG. Leak down was 1% on both cylinders, the front was 200# and the rear was 190# Is this telling me something is going wrong but has not gotten there yet? Harley says it is in normal range, but I get the feeling if I had to pedal the thing they would say its normal. Please tell me what you guys think. Mike.
Road Captain
Joined: Aug 2009
Posts: 619
Likes: 3
From: In Garage
I had 4500 miles on my ride before I dug into the engine. 200 and 190 seems high on a stock bike. Uless I missed a sente nce.
anyways I had a 5% difference in my cylinders. Once apart I found a lot of carbon. About a good 16/th of an inch. Im not exaggerating. I posted a pic on this site some were. I tried seafoam and it did not work I had to take a wire wheel to it to get it off the pistons. The chambers looked clean. Hmph go figure.
Now im at exactly the same comp. On each piston. I did get new pistons and went bigger : )
anyways I had a 5% difference in my cylinders. Once apart I found a lot of carbon. About a good 16/th of an inch. Im not exaggerating. I posted a pic on this site some were. I tried seafoam and it did not work I had to take a wire wheel to it to get it off the pistons. The chambers looked clean. Hmph go figure.
Now im at exactly the same comp. On each piston. I did get new pistons and went bigger : )
HDF Community Team
Joined: Jun 2006
Posts: 12,774
Likes: 2,606
From: san antonio
A more intresting question would be how his measured compression compares to calculated to see which cylinder is off.
Last edited by djl; Jul 17, 2011 at 06:46 PM.
Road Master
Joined: Jun 2008
Posts: 868
Likes: 1
From: Trenton,N.J.
I just had a compression check done on my 2010 Dyna SG. Leak down was 1% on both cylinders, the front was 200# and the rear was 190# Is this telling me something is going wrong but has not gotten there yet? Harley says it is in normal range, but I get the feeling if I had to pedal the thing they would say its normal. Please tell me what you guys think. Mike.
Any head work??
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Cruiser
Joined: Sep 2007
Posts: 101
Likes: 0
The engine has not been messed with at all. No other work done other then a stage1, and a really thorough break in. Alot of roll on and roll off. perhaps the numbers are high because of the carbon? I see different tricks to get rid of it, like water spray, seafoam spray, ect. Can the water spray damage a piston?
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HDF Community Team
Joined: Jun 2006
Posts: 12,774
Likes: 2,606
From: san antonio
The engine has not been messed with at all. No other work done other then a stage1, and a really thorough break in. Alot of roll on and roll off. perhaps the numbers are high because of the carbon? I see different tricks to get rid of it, like water spray, seafoam spray, ect. Can the water spray damage a piston?
Thread Starter
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Cruiser
Joined: Sep 2007
Posts: 101
Likes: 0
The dealer did the test so I may go back and ask the tech. In any case I think I will do the compression test myself and see what I get. I have to get the proper gague parts, so we will see! the whole (EVERYTHING IS FINE) thing just does not sit well with me.