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Discussion Starter · #1 ·
Greetings,

This may seem like an odd question, but my 68 bonneville has always had crankcase vent tube discharge, (you know that milky white goo, that is found on the ground after a good ride). But here lately there is no discharge goo. I run the vent tube to the "T" then run it out around the rear fender. The other port of the "T" is connected to the oil tank. There is air puffing out of the tube while its running. I built the engine bout 3000 miles ago.

I recently changed the oil and drained more than a cup of oil from the crankcase, indicating wet sumping, so I pulled the regulator, it was fine, so I pulled the oil pump. I found the oil pump spring caps to be loose. I reseated the balls, and tightened the caps with a drop of blue lock tight. It is not wet sumping now, good oil flow to the top end, has good compression, and seems to be running fine.

I don't know why the crankcase vent has cleared up???

Thanks for all replies.
 

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Your old oil was full of water, creating a sort of mayonnaise
When you changed the oil, you did the bike a favour.
If you do a lot of short runs, the bike will generate moisture in the oil.
If you can't boil it off, due to short runs, change the oil more frequently than recommended - it costs money but is a lot cheaper than using nasty oil
 

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Discussion Starter · #4 ·
Your old oil was full of water, creating a sort of mayonnaise
When you changed the oil, you did the bike a favour.
If you do a lot of short runs, the bike will generate moisture in the oil.
If you can't boil it off, due to short runs, change the oil more frequently than recommended - it costs money but is a lot cheaper than using nasty oil
This bike has always discharged goo. I think gp is probably right. I don’t know when it actually stopped, but is was long before I changed the oil. I changed the oil because it was due an oil change. All my rides are short (20 miles or less).
 

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Hi 10drum, The intake camshaft is hollow & has a 1/4" hole drilled in it 1/4" to the right of the right intake cam lobe.

The left end of cam is open to the disc breather valve. There are actually 2 discs both with 2 small holes rather triangular in shape. One disc notches onto left end of intake cam & has spring which presses it against the 2nd disc. The 2nd disc is located behind the cam bushing in left crank case. Behind this 2nd disc is the passageway that goes to the steel tube the breather hose fits onto.

The holes in the discs are situated such as when pistons fall they align & air/fumes are expelled from crank case area. These fumes must pass through the 1/4 hole in cam & the disc hole. A little fumes may pass by the bushing, but most go through cam.

As pistons rise the holes are blocked due to the rotation of the 1st disc. This creates a small negative pressure in crank case.

The rod bearings are always spewing oil & the flywheel picks up oil & flings it up onto cams. So the cams tend to have oil sprayed on them. Some of this oil enters the 1/4" hole in cam. The rotation of cam can act as a centrifuge of sorts & the oil can be thrown out the cam as it rotates so in practice not all that much oil gets into the rotating discs & out the breather pipe.

However if the sump has too much oil or motor has too much blow by the system gets more oil than it can handle & some oil can be lost out the breather tube. On some motors this can be a fair amount of oil. One bike I'm involved with would often spit a 2" puddle on the ground after shut off or sometimes at start up. Most oddly was often unpredictable.

The milky goo in the oil is from water in the blow by oil. I was told in apprentice school approx. 1 gal of water is produced per 1 gal of fuel consumed. At work in practice I've found this to be mostly true. Plus condensation from temperature differences. Most the water is turned to steam & sent out the exhaust pipe. But some goes by rings with the blow by gases. Plus condensation in crankcase. Cold winter days will dramatically increase moisture in both exhaust & blow by.

If you corrected too much oil in sump, that can explain why less oil is expelled from breather hose. I cannot explain why you are getting so much less moisture now. Is it because of the warmer weather or possibly from lower humidity??

I always though it better if the blow by oil could be sent back to oil tank, but the froth tower on tank is higher than fender so it's not possible to raise breather hoses & T fitting to accomplish this.


On an aside the spring for the crank sprocket faces the sprocket to reduced the chance of oil being sucked from the primary due to the lower pressure in the crank case. On a really good sealing set of rings & good valve stem clearance, at times if you gently place finger over end of breather hose, you can feel the low pressure suck your finger towards hose. Which good rings this system works decently, but can still spit some drops now & then. Moisture/condensation will often be spit on cold starts. I've observed this many times.

The later primary breather system is plumbed such the blow by oil is mostly trapped in primary case & sent back to oil reservoir. Any oil that gets into breather hose simply drains back into the primary case. It's very rare to see primary breather bike to spit oil out breather. Moisture/condensation is spit out on cold starts. A good 3 drops to a 1" circle. Starting motors in 20s & 30sF this is expected. I've seen it many times.

The bad part of the primary breather is much condensation can collect in the primary case & it's common to see rusted steel parts on the clutch & the like. Short trips can really build up the condensation in primary. So there are trade offs.

In any case good you are now having good results.

Looking at cams at swap meets some intake cams have a roll pin installed in the 1/4" hole. The roll pin sticks out a good 3/16" maybe more. I don't know why or what motors had the roll pin. Looks factory & I've seen it many times. My hunch is it allows less oil to enter cam. Again, only a hunch, I could be very wrong.

Don
 

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Yes, the purpose of the pin was to reduce splutter from the breather. I don't know when this was implemented, but in regard to earlier preunit engines,Harry Woolridge's book " The Triumph Trophy Bible" says, re '56 models "To reduce oil splutter from the engine breather outlet, the inlet camshaft only had one breather hole, fitted from 72123 (22/2/55 ).
 

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Discussion Starter · #8 ·
TR7VMAN, thanks for making me think. I've wondered why some cams have that tube and others don't. You've also made me think about the the placement of the "T". There's been times I've noticed on unmolested bikes (a rare find indeed), that the the "T" is installed adjacent to the top of the oil tank, plus, I've seen different T's. Some of the T's have a smaller hole in one of the ends.

As I said above, "the bike seems to be running fine", and it does, but I have noticed different sound(s). At first I thought it was the primary, so I checked that, then I thought it was because I have been building, and experimenting with a BMW R75/5, and I'm just getting use to the sound of the Beemer??? but "sputter" is what I am hearing, thanks for labeling the sound Stephen. I think this engine, or at least the crank, has been raced in the past, because the primary end of the crank is threaded, I guess so that it could be run without the rotor. I may dig deeper into this, come winter.

Thanks for the replies
 
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