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.

 

Sounds like "it is in normal range" to me!

 

1% leakdown is well within range, 5% to 10% is great. I wouldn't like the fact that there is 10# difference from one cylinder to another as they should be identical. However, manufacturuing tolerance differnces, like head chamber volume could cause that and it is within acceptable range of 10% variance between cylinders. Top end is in excellent condition.

 

I did not like the 10# difference either, and that is why I asked. Being a 2010, and having misting funeled back into the air intake, there is some carbon build up on the pistons. I suppose some sea-foam, and a hard run with another check is in order. Thanks for writting back. Mike.

 

Thats 5% and would be considered normal.

 

Sounds normal to me. The 10 lb split between the ft and rear I'd rerun them to see if they come up the same. Are you looking for a problem or just checking it out

 

5% on a production built motor seems pretty good. Lots of variables to consider, the slightest difference can change the numbers a bit. The fuel in the intake and carbon on valves could either be timing is slightly off or a your bit rich. Maybe a tune?

 

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.

 

Oil consumption, not good. 6500 is definitely broke in. I now know why you done leak down and compression. Would have to be rings, valve seals, or possibly crankcase ventilation. Your tests kinda rule out rings. JMO though as my knowledge is more in Hi-Po V8's.

 

It all seems to point to the air intake. Looking for another solution in oil product, or air filter backer plate. No one seems to have a fits all fix for this problem. Maybe I will just ride it till I die of old age, or they stop making sea-foam. Be well all!!!!!!.

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