[]I have a 2005 Road King with 38500 miles. I developed a spark knock a while back andnow I noticeitis starting to use oil. When I changed my spark plugs, the front plug had oil around the threads. The spark knock seems to be coming from the front cylinder where the oily plug was. I am told there is a filter in each head that filters oil from crank case pressure. I have heard this can cause oil to leak from the breather if it is stopped up. Could this also cause oil to leak around valve seals? Bike runs fine otherwise. Is there a way to check for bad valve seals? How much compression should I have per cylinder to eliminate a ring problem? Any help would be greatly appreciated.

 

ok number one buy the service manual from HD.
It explains the breather system in detail.
why did you get a spark knock (ping, detonation)
Are you carb or F.I.
what mods did you do?
If you are getting oil in the cylinder it can come from only three (common)places and breather is not one of them, although it can add to the problem.
1. past the rings
2. through the valve guides
3. Head gasket
or worse a cracked cylinder or piston with hole burned through from detonation.
Now if you did something to cause an excessive lean condition you could have severe internal
problems. And that is your bad.
I'm not expecting you to be a mechanic and know all the ins and outs.
But I do expect you to BUY the HD manuals (service and electronic) for your bike.
They explain a lot and have valuable info.
Unless you are never going to work on it yourself.
In which case you shouldn't be asking the last few questions you asked.
but since you did.
I haven't looked it up myself yet but Thunder Mountain says 06 TC88 should be about 160 psi
on compression, guess someday when I need the info I will verify it.
If the breather fails or gasket is installed wrong, it can allow excess oil to accumulate in the rocker boxes. so if you have bad / weak seals, valve guides yes it can leak down.
If spark knock is bad enough long enough the excess pressures and heat can;
crack pistons and heads, burn hole in the piston, warp the head and damage rings.
Now go buy the manuals.

 

05's were known for bad valve stem seals. Would bet that's your problem. Might be time for an upgrade? For example, if considering having the heads ported, Bean at Big Boyz will replace the seals at part of the porting job.

I have exactly what you described with the oilly/crusted spark plug (mine was the rear).

Search the forum for valve stem seals - will find a bunch of info.

 

I had oil on the plugs on an 05 RKC. There was a recall to replace the valve guides. Check with your dealer.

 

my bike is efi, i am thinking the spark knock is from oil around the plug and is not getting a good ground, only does it when loaded and a hot day. thanks.