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[Saljemar]

I have a very small amount of oil seeping out from the rear side of my rear cylinder below the head gasket.  It was determined that I have a slightly porous cylinder.  After a couple hundred miles 5 fins wil have shiny brown staining and a little has dropped to the top of the lower cases.  I was planning on having it replaced after the riding season.  Has anyone had this same problem and do you think it affects performance?

[sadunbar]

I have a very small amount of oil seeping out from the rear side of my rear cylinder below the head gasket.  It was determined that I have a slightly porous cylinder.  After a couple hundred miles 5 fins wil have shiny brown staining and a little has dropped to the top of the lower cases.  I was planning on having it replaced after the riding season.  Has anyone had this same problem and do you think it affects performance?

Just curious - how was it determined you have a porous cylinder vs. a seeping head gasket?  I've never seen a porous cylinder leaking as you describe, but have seen plenty of seeping head gaskets, especially on the rear cylinder, which would create the condition you are seeing.

To answer your question, as long as the seepage (regardless of its origin) is minor as you describe, other than the hassle of cleaning it all the time, it could likely wait until the end of the riding season.  I'd pull the spark plug and see if it's at all oil fouled.  If it is, then I'd repair it now vs. waiting.  If it's a warranty issue, it shouldn't take any time at all to have it repaired... 

[Saljemar]

There is nothing on the spark plugs.  Before I brought it in I took a magnify glass and could see nothing coming from the head gasket, but starting from 5 fins below the head gasket.  They put it on a dino and after running it saw seeping through the cylinder.

[mark]

I'd probably address the problem now just so I'm not dealing with oil leaking over the engine, dealing with possible staining, etc.  even if you get it fixed during the riding season, how long will you be w/o your bike....a week?

[Saljemar]

I think I will have it done now like you said.

[HD Street Performance]

Interesting
Is your motor stock? Stock head gasket?

[Saljemar]

Totally stock except Fullsac's 1.75" baffles.

[grc]

If you are saying the oil is leaking at the rear center of the rear cylinder, there isn't any kind of oil passage back there to leak.  The cylinders only have one oil passage, and it's the return passage for oil draining back from the head.  It isn't located where you indicated you see a leak.

Check with an auto parts store for a leak detection kit.  The kind I'm thinking of includes a special dye you put in the oil and a black light.  You might be surprised to find the actual leak isn't where you see the oil collecting on the fin.

Jerry

[FLH91]

Thats a great idea!

[sadunbar]

If the front wheel were 12 o'clock and the rear wheel were 6 o'clock, there is an oil passage in the cylinders at (approximately) 11 o'clock and 7 o'clock The thickest part of the cylinder is between the outside diameter of the oil passage and the outside wall of the cylinder.  It's almost unfathomable a cylinder could be so porous it is leaking thru this area.  I'll guess it's a rocker box gasket or head gasket seeping and collecting on the cylinder fins where it becomes noticeable.

[HILLSIDECYCLE.COM]

Have seen porosity in the cast iron liner in the past, (never in a 4" OE HD casting, though).
That created an oil consumption/smoking issue.
Scott

[sadunbar]

Have seen porosity in the cast iron liner in the past, (never in a 4" OE HD casting, though).
That created an oil consumption/smoking issue.
Scott

Leaking from a porous cylinder near the oil passage into the cylinder bore thru the liner - yes, seen that and the result is as you suggest - oil consumption/fouled spark plug/smoking...

Leaking from a porous cylinder near the oil passage out of the cylinder to the fins - never seen that.

Of course, there's always a first time and never say never...     

[HILLSIDECYCLE.COM]

Hate it when that happens.............

[Saljemar]

After reading the comments I decided to see if I could find another reason that I was getting a wet area on the back side of my rear cylinder and not change out the cylinder because the dealership said it was porous.  The first thing I checked was the header clamp and the nuts were not very tight.  I tightened them up and as of now do not have a wet area on the back side after driving a few hundred miles.  The bike has 5500 miles so I brought it to the dealer since it was under warranty, but won't be so fast next time and will do my own diagnosis first along with some help from this group.

[HILLSIDECYCLE.COM]

You tightened the exhaust flange nuts, and now it is dry?
Scott