Ace 100 Crankcase breather

[louiez101]

I noticed that I have excess oil coming from my crankcase breather hole, why???

[Bullfrog]

A few possibilities, most of which are benign - but one is a serious symptom.

First, the benign possibilities. Did you recently change oil or add oil? An over-filled transmission will leak oil out of the breather. The spinning gears more easily fling oil up to the bottom side of the breather and the warming engine creates internal air pressure which is vented out the breather carrying the "flung up" oil with it. A start up in cold conditions can do the same sort of thing. Note that when the excess oil in an over-filled transmission has been forced out of the vent, the leakage will stop.

Now for the serious possibility. An air leak between the crankcase area of the engine and the transmission cavity can pressurize the transmission cavity ALL THE TIME. In this case, the oil leaking out of the transmission breather vent won't stop until almost all the oil is gone - ie, there will be oil on the top of the cases EVERY time you start the engine. So this is bad simply from the stand point of being messy and always losing oil from the transmission. But it gets worse. ANY leak into, or out of, the crankcase area of the engine must be corrected because two-stroke engines must have air-tight sealing. The oil leaking out of the breather might be a prime indicator that you have such a leak.

Solution? Do a crankcase pressure test to confirm whether or not you have a leak. It is quite possible that you do . . . and that it might be a failed clutch side main seal. Since the clutch side seal can be replaced without removing the engine from the frame, that would be a relatively easy fix.

The sentence above has been edited to be in red because it is NOT CORRECT. While the magneto side seal can be replaced with the engine in the frame . . . if the clutch side seal has failed, the engine must be removed from the frame and then it must be fully disassembled in order to replace the seal. I apologize for the error.
Ed

[viclioce]

Nice points! ; D Victor

[hodakamax]

I think Ed has covered all the points that are likely. One other weird one can be water in the oil from emersion or even condensation. When you start the engine the combination of oil and water emulsify and as the engine heats up the emulsion expands blowing out the breather. This usually is a one-time event as the water evaporates when heated. In this case the oil will appear milky. An unlikely series of events but it does happen.

Max

[hodakamax]

A few possibilities, most of which are benign - but one is a serious symptom.


Solution? Do a crankcase pressure test to confirm whether or not you have a leak. It is quite possible that you do . . . and that it might be a failed clutch side main seal. Since the clutch side seal can be replaced without removing the engine from the frame, that would be a relatively easy fix.

Ed

What? Which clutch side, the clutch lever side or the actual clutch assembly side? Just asking! (and trying to catch you.)

Max

[Bullfrog]

Good one Maxie! Um, the clutch side of the crankshaft.
Ed

[ossa95d]

My recollection is that the clutch side crank seal is inboard of the bearing.

[Bullfrog]

DOH! Absolutely correct. I screwed up BIG TIME! I was thinking one thing and typing another.

CORRECTION: It is the magneto side main seal which can be replaced with the engine in the frame. In this instance, the clutch side main seal is suspect and the engine must be removed from the frame and the cases must be split in order to replace that seal if it has failed.

My apologies for the mixed up auto-pilot response.

. . . and now I fully "get" Maxie's hint.

Ed

[hodakamax]

Gotcha

Maxie

[[email protected]]

I have exactly this problem on my 96 Dirt Squirt, but only when the weather is cold. In summer no problem, so in the winter I simply take out the oil dipstick for the first two or three minutes of warm up (stationary of course) then switch off the engine and replace the dipstick. I've tried different levels of oil and even different oils, but nothing stopped the ooze out of the breather when the weather was cold.