Blow-by and crankcase ventilation-fuel contamination?

[ekvh]

I started to post this in chilidawgs thread and realized it wasn't related to his topic, so throwing this out for to-cold-to-go-outside discussion. This is in regards to excess pressure in the crankcase: I wonder if any fuel gets by the rings in blow-by? Never thought of that and its potential threat to oil contamination. I am pretty sure mine has more blow-by than it should. It hasn't blown the filter out of the vent tube yet, but you can feel it puff when you remove the filter and rev it. I'm tempted to throw some new rings in after watching Aussiegold and Bronko37's videos. I need to look at my clutch also.

In my engine, I'm talking about the 1200 that I shaved the heads 0.025", I am wondering if I am losing what I was trying to gain, from weak rings. Admittedly my shop practices are in the rank amateur stage and I may have gotten some grindings into the mix. I smeared grease around the piston when grinding the valve reliefs, then wiped and washed it out. My compression was in the 140-150 range. I advanced the cams and got it to come up some, but maybe under load it's just passing the energy by. It would be nice to see the rings, whether one has cracked or if they're just warn out.

I may just prep my 87 1200 and put it in so I have something to ride and then tear down my current 85 engine. If the 87 has noticeably more snort, I'll know without tearing it down.

 

[AApple]

Pretty much ANY internal combustion engine is gunna have some "blow by"....compression gasses getting by the piston rings. A small amount of fuel, both raw and diluted/burned will be present. No escaping it.
One thing that can also cause vapors to blow out of the breather is simply the rotation of the crankshaft, pushing/pulling the pistons up/down. This creates pulses of air inside the crankcase, which can/will create puffs out thru the vent tube. The main difference between the crank created pulses, and blow by is, blow by is usually a smoky vapor. These engines have a vapor trap can on them to catch the vapors as they turn back into a solid oil, from the factory...

GL4a

• AApple
• Jun 5, 2013

So basically, SOME air/smoke coming from the crank vent is to be considered normal. If there is so much blow by that it looks like a Cheech & Chong movie, then it would most likely also be smoking from the tailpipes, the plugs would foul easily, and the engine would not run well. This would constitute too much blow-by. I actually still have a small tester to check blow by pressures in automotive engines. You just pull the PCV valve out, and attach this little gauge, and it moves a little ball up in the register. The higher the ball goes, the more blow by there is. The tester is calibrated to show from "Normal" to "Excessive".

 

[Ansimp]

It might just be increased compression from your shaved head causing more blow by from your original rings. If it runs well I would just go for a more elaborate catch can style system to recover any lost oil.

 

[mcgovern61]

What are the compression readings now?

 

[joedrum]

hmmmmm boxer motor are worst at oil contamination than other motors ..the stock carbs dont help this with there leaking problems ...ive noticed on hooch the oil stay in good shape longer than other oldwings ive had with stock carbs ...and the sidestand deal pays a part here too ...interesting discussion

 

[Tom_Charlton]

+1 on the sidestand. Leaving your Wing on the sidestand lets oil lay against the bottom of the left side pistons and may encourage the carburetors to leak into the manifold. I always put mine on the center stand.

Another thing to avoid is short trips that don't get the engine up to normal operating temperature. Water vapor in the lower end can build up and cause rusting inside the engine if the oil temp doesn't get above 212F.

 

[bronko37]

Also remember, my compression readings were incredibly low. Also, with my upswept exhaust system what I didnt realize is that the exhaust is pointing directly at my rear signals. On each and every ride I would have oil on the signals themselves. Also the case was leaking on the split line. There were a lot of things pointing in the direction of new rings.

Your compression on the other hand seems to be pretty good. Factory is 170psi, and the book suggests a rebuild below 140psi. I was at 90psi but you are right there in the good range. Was the compression really low before you milled the heads down?

However, if one is so inclined to tear into a motor and has the skills tools and time to do it, I would encourage them to try it. It has been a really rewarding experience and I sure have learned a lot along the way.

May be time to do some homework here first tho and see whats going on here.

 

[bronko37]

PurpleGL1200I » Wed Feb 10, 2016 10:17 pm[/url]":3e6facc2]
+1 on the sidestand. Leaving your Wing on the sidestand lets oil lay against the bottom of the left side pistons and may encourage the carburetors to leak into the manifold. I always put mine on the center stand.

Another thing to avoid is short trips that don't get the engine up to normal operating temperature. Water vapor in the lower end can build up and cause rusting inside the engine if the oil temp doesn't get above 212F.

Lots of folks love the center stand, my bike doesnt have it on it so I block it up level when she is just in the garage. I also read one time that some folks lean the bike hard right after shutting it off for a second to let the excess oil in the cylinder walls and heads drain into the case. Then the put it on the side stand. I dunno if it works or not, but the logic seems sound to me.

 

[ekvh]

I tip mine right and then side stand it. Works for me as long as I keep the oil to the middle of the marks, or about 1/2 court below full. Mine doesn't use much, if any, oil. Compression on the 1200 is recommended to be 156-213 psi, so I think mine is a bit low. Oil sprayed helps it the readings some indicating rings. It runs pretty good, but I have to get it tip-top in case I run in to Joe.

 

[bronko37]

Sounds to me like you've already made up your mind, lol. I know once I decided to tear into mine nobody was gonna tell me different. If you feel so inclined I say go for it, it really isn't that bad to do. Just one process at a time until it's done. Everything clean, organized, and fully inspected.

 

[ekvh]

"Everything clean, organized, fully inspected." WHAT????? lol

 

[dan filipi]

Lean right? Lol. This is a flat engine. What good does this do?

 

[bronko37]

dan filipi » Thu Feb 11, 2016 8:47 am[/url]":1yy17dhc]
Lean right? Lol. This is a flat engine. What good does this do?

The theory Dan is that any residual oil that is left in the cylinders and head upon shut down will drain back into the case by leaning it right before you side stand it left. If you just side stand it left and oil is sitting in the cylinders it can creep past the rings. Its supposed to help with the smokey start up nature of these flat engines. Supposed to.....

 

[ekvh]

Agree, I shut mine down sitting straight up, remove helmet and gloves. This allows the majority of the oil to drain, hot oil, to drain. Then lean it right as much as you dare for 5-6 seconds and side stand it right. Of course if your bike blows smoke out the right side after doing this, it probably is something else. Mine will smoke some on the left if I forget to do this. Not always, probably only when the ring end gaps are towards the bottom. YRMV

 

[joedrum]

im with dan ..ill do no turn off dance everytime i stop the bike ....i really like the front ride off stand :BigGrin:

 

[dan filipi]

Lol, picture a group of oldwing riders stopping at the pub and they all lean right after shutting down :smilie_happy:

Anyway, I agree to shut down with the bike upright and not on the sidestand because oil will fill in the left head cover.

 

[toytender01]

Well you see, after riding for a while your shorts get bunched up, and the lean right helps too straighten them out......... :smilie_happy: :smilie_happy: :smilie_happy:

 

[julimike54]

toytender01 » Yesterday, 11:18 am[/url]":1nldf2md]
Well you see, after riding for a while your shorts get bunched up, and the lean right helps too straighten them out......... :smilie_happy: :smilie_happy: :smilie_happy:

That thar is funny! :yahoo: :smilie_happy: :Egyptian: :BigGrin:

 

[mike in idaho]

When you shaved the heads, the decrease in the center to center distance of the timing sprockets retarded the valve timing. That will lower the compression numbers a bit(later intake valve closing). An offset key in the crank sprocket could be used to get the timing back to the original specs and the compression up a tad.

 

[ekvh]

By my calcatrations the shave dropped valve timing slightly less than one cam degree. I advanced it as much as five camshaft degrees, which is ten crank degrees and it bumped compression nicely and moved power band down. I've just wondered about blow-by and whether the gains are lost in dynamic situations. ( squirting by the rings)

I guess I could put some kind of gauge on the vent. If rings are good, I shouldn't see any real change in pressure??? It might cause a bit of pressure on seals.