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[stekat]

Shortly after I bought my '07 CVO, I took a compression reading for reference.  For a 9.3CR motor it was reasonable at 150psi front & rear.  After the dealer repaired the rear cylinder oil leak (the first time), I rechecked the compression.  The front was still 150 but the rear was now 210psi.  I quickly found that the wires out of the rear compression release had melted and shorted out on the head bolt.  I would not have found the bad compression release without a compression check; the bike still started fine.  The dealer said that probably most of the 110" CVO's have bad compression releases and don't know it.  He also said that S&S runs their wires up thru the rocker box to prevent just this kind of failure.

My point in all this is that these engines, with only 9.3CR, must have a very tight cam in order to trap that much pressure.  It also partially explains the numerous complaints of pinging, overheating and mechanical failures we've all had.

Thought you'd all like to know.

[evilroadking]

You know, when i installd my SE 50MM Throttle body, i notice a potentional problem with relay wires. I had some thermal wire wrap sheidling laying around and put it to use. It's good to know that i wasnt being parnoid and overprotecting something.

[erniezap]

Obsessed or paranoid people on this site?  You're kidding, right?   

[evilroadking]

I'll stick with Obsessed. Parnoid makes feel nervous and obsessed.

[grc]

Shortly after I bought my '07 CVO, I took a compression reading for reference.  For a 9.3CR motor it was reasonable at 150psi front & rear.  After the dealer repaired the rear cylinder oil leak (the first time), I rechecked the compression.  The front was still 150 but the rear was now 210psi.  I quickly found that the wires out of the rear compression release had melted and shorted out on the head bolt.  I would not have found the bad compression release without a compression check; the bike still started fine.  The dealer said that probably most of the 110" CVO's have bad compression releases and don't know it.  He also said that S&S runs their wires up thru the rocker box to prevent just this kind of failure.

My point in all this is that these engines, with only 9.3CR, must have a very tight cam in order to trap that much pressure.  It also partially explains the numerous complaints of pinging, overheating and mechanical failures we've all had.

Thought you'd all like to know.

Copy of cam specs attached, verifying your gut reaction. 

Jerry

[stekat]

Thanks Jerry, that's very helpful.  If I had more guts, I'd trash the warranty, re-cam and re-tune the way it should be done.  Unfortunately, with the failures I've already had, I don't trust the engine in any state of tune and am afraid to dump the warranty.

[Chief]

OK, I ran a check this afternoon. I got 115 / 182 on the rear using the starter button and then jumping the starter to keep the CR closed. The results are about what I would expect (182) for a 9.3 motor. The front showed 175/175 indicating that the front CR is not functioning since there is no difference from using the starter button (CR's open) and when I jump the starter (CR's closed).

Time to see the dealer again. Oh, and the rear cylinder base o-ring appears to be leaking again, or maybe that is still.

[stekat]

Chief, thanks for your numbers, very interesting.  I wonder why they are that much lower than what I got?  Did you test with the throttle open?

I too have oil leaks at the bottom of the cylinder, twice.  The second time they replaced the cylinder and used a torque sequence recommended by Cometic (the gasket maker) with Harleys blessing.  Harley said that they would probably change to the new specs soon anyway.  With 1000mi since the new cylinder, so far I have no leaks (yet).

I just noticed and posted on the size of the breathers; "110 breathers very small".  High internal pressure may be part of the oil leaking problem.

[Chief]

Chief, thanks for your numbers, very interesting.  I wonder why they are that much lower than what I got?  Did you test with the throttle open?

I too have oil leaks at the bottom of the cylinder, twice.  The second time they replaced the cylinder and used a torque sequence recommended by Cometic (the gasket maker) with Harleys blessing.  Harley said that they would probably change to the new specs soon anyway.  With 1000mi since the new cylinder, so far I have no leaks (yet).

I just noticed and posted on the size of the breathers; "110 breathers very small".  High internal pressure may be part of the oil leaking problem.

I would assume the difference is in the gauges. Yes, the throttle was open on all tests. The numbers I got are right in line with what I got on my previous 88. Same gauge, so if there is an error, at least it is consistent. The absolute number is not important as I'm only looking for a comparison as the motor wears. As long as the F/R balance stays pretty consistent, then everything is OK.

As far as the small holes in the breathers, there isn't a whole lot of air coming out of them, so high flow rates aren't necessary. Think of them as bleeders and not free flowing vents.

[stekat]

I'm not sure I follow you.  I've run and built hi perf engines all my life.  Adequately removing crank case pressure will show demonstrable benefits on a dyno.  Are you pulling from some source that indicates low internal pressure in these engines?  From my experience, a pencil lead size breather on a 110" motor doesn't do it.

[Chief]

I'm not sure I follow you.  I've run and built hi perf engines all my life.  Adequately removing crank case pressure will show demonstrable benefits on a dyno.  Are you pulling from some source that indicates low internal pressure in these engines?  From my experience, a pencil lead size breather on a 110" motor doesn't do it.

In the motor, where is the pressure coming from? The main source of air being introduced into the motor is blow-by past the rings. The idea behind the unbrella valves in the rocker boxes is that air can get out, but not in. When the pistons travel down, they will force air out. When they move up, the umbrella valves are closed and the crankcase starts pulling a vacuum. Once equilibrium is established, the only thing that needs to get through the breathers is what gets past the rings. As long as you've got good rings and a good seal, there's not a whole lot of air volume passing through the breathers.

I wouldn't be overly concerned with the size of the breather hole. It's been a small hole for a long time and seems tp work pretty well.