Bottom End Pressurization Problem

[Fred W]

Alan (ionbeam) disassembled his motor due to a CCT failure and the resulting bent valves, not due to a loss in ring compression. He only noticed the gooked up rings because he was in there already and decided to look at the pistons and lower end. I don't think he knows for sure how much his messy rings were leaking, but I'm sure he'll let you know full details.

 

[ionbeam]

...my 190k mile FJR developed an intermittent problem where my left leg would suddenly be covered with oil...replaced O-rings...
• The primary leak is coming from the where the stator wires exit the side cover, but it's also leaking to a lesser extent from the airbox by way of the crankcase breather....

• The bike had been consuming a very small amount of oil for the last 1-1/2 years or so...Doesn't burn during normal every day use.

• Compression was 215psi on all cylinders on 6/15/13. Compression is now 175psi on 1 & 2, 180psi on 3 &4. Compression raises to 240psi with a little oil in the cylinder, so obviously there is a ring issue...

• ...Ran through a bottle of Yamaha Ring Free over the course of the trip home, made no difference...

Alan (ionbeam) disassembled his motor due to a CCT failure and the resulting bent valves, not due to a loss in ring compression. He only noticed the gooked up rings because he was in there already and decided to look at the pistons and lower end. I don't think he knows for sure how much his messy rings were leaking, but I'm sure he'll let you know full details.

I wonder if you actually may have two different, unrelated issues. When you say you replaced 0-rings do you mean the one on the oil filler plug?

If the breather hole is free into the engine, the breather hose is clear and the breather hole is free going into the air box I don't see how the engine can build up internal pressure. I would think that compression blow-by past the pistons which is bad enough to cause oil to be driven up and out of the top of the engine would also cause a driveability problem. How did the plugs look? If they aren't oily I would doubt compression blow-by.

The only way to stop the oil from leaking at the stator is to pull the cover and seal it again. I have had my stator cover off several times and have had a b!tch of a time getting it back on without leaking at the wire feed-thru, it's kind of a kludge the way the rubber piece needs to go in. If your stator wires have a sleeve above the feed-thru like this stock stator does, check the sleeve to see if oil is wicking up the wires, this happened to some '03 & early '04s. In this picture it looks like the wires are well sealed in the rubber plug.

I had no reason to suspect that I had a ring problem, my bike started well and charged hard. I was running my bike at New England Dragway, so the engine definitely wasn't babied. From my CCT disaster thread:

** I've got a puzzle here. When the cylinder head came off, the mechanic whistled and said that I shouldn't have let my motorcycle sit for a year or two before the repair. WTF?!?! My poor bikie had just been taken off the road a few weeks ago. When we looked at the pistons and the bottom of the cylinder head it was massively rusted. There was zero sign of coolant, just rust, rust, rust. During the final tear down it was clear that the rings were so rusted and frozen into the pistons that they had to go. My motorcycle was in my garage when the BIG BANG happened and stayed in my garage (to the dismay of my car) until it went for repair. It was humid for a couple of weeks, but dang, it looked worse than I would have expected if I had filled the cylinders with sea water. Any ideas what happened to cause all the rust? I can assure you that my engine had experienced regular elevated RPMs and higher engine loads daily. Our local gas stations have finally gotten rid of MBTE and replaced it with 10% ethanol which does pick up water. ????

Note that aluminum doesn't rust and we misspoke in calling the orange fur 'rust'. I had been using Tachron every few tanks to prevent exactly what we found. What ever that stuff was, fuel residue, rust or algae it had things frozen together.

 

[Bionic Pelvis]

If the breather hole is free into the engine, the breather hose is clear and the breather hole is free going into the air box I don't see how the engine can build up internal pressure. I would think that compression blow-by past the pistons which is bad enough to cause oil to be driven up and out of the top of the engine would also cause a driveability problem. How did the plugs look? If they aren't oily I would doubt compression blow-by.

This is what has me scratching my head. It's not just a dribble or wicking up the wires, it's a pressurized spray (but only sometimes). The stator wasn't recently replaced, but it was less than a year old. It's not leaking out of the top of the engine, unless you meant by way of the breather & stator grommet, and it is definitely leaking out of both. After I siliconed the grommet it leaked more heavily out of the breather, so it was easy to identify that as a second source of the leak and lead me to suspect something was causing pressurization. The spark plugs looked fine, it wasn't smoking at all, started easily, performed normally, exhaust header & ports are all dry, so on. 175 is still a fair amount of compression; is it enough to keep most of the oil out of the combustion chamber, but with just enough blow-by to pressurize the bottom end under the right conditions? It's definitely not a normal, run-of-the-mill "compression is getting low" scenario.

 

[Donal]

If it were me, I would rig up some kind of temporary additional crankcase breather. The easiest thing to do would be drill a hole through the 'oil filler cap' to fit any available hose you can lay your hands on. Use some sort of adhesive (silicon sealant) to fix it in place and then route the open end to the air box.

If that makes a difference then consider replacing the existing breather hose. You will still need to seal the stator wires at some time.