72 Crankcase

For the life of me I'm going to beat this dead horse till its gone to dust and floating in the wind.

I want a picture, or 4, in detail, showing the exact area and location of the oil pick up on a modified 1972 crankcase.......please.
Don't tell me to go here or there. If ever I can return such a demanding favor, I will GLADELY return it. Even if that mean sutting the hell up. I will......for a while anyway.

O.K. go back to the first thread and I posted it there, Sorry I was doing it when you started this thread, Chuck

pvisseriii said:

For the life of me I'm going to beat this dead horse till its gone to dust and floating in the wind.

I want a picture, or 4, in detail, showing the exact area and location of the oil pick up on a modified 1972 crankcase.......please.
Don't tell me to go here or there. If ever I can return such a demanding favor, I will GLADELY return it. Even if that mean sutting the hell up. I will......for a while anyway.

Click to expand...

Your engine number is very early in the '72 range which supposedly started 200000. The first combat engine was somewhere around your number. Where is your crankcase breather 1) lower back side of the left crankcase half or 2) left crankcase half at the end of the camshaft? If camshaft breather you probably have the large sump screen.

I modified my combat engine oil pickup per what is posted. Looking back over 12 years and 26,000 miles I would say it wasn't necessary. So what if the oil goes up the "combat breather", still goes back to the oil tank.

Thanks so much for your patience, Chuck.

Yes, It is getting clearer. I looked back at the GrandPaul's testmule project and saw that there is something a little different. There is a hole with a counter bore which appears to match up to the the hole you pointed out on the timing side. Is this just a matter of preference where as he drilled a hole rather than machining down to meet the hole adjacent.

Dave kicked me off his thread. :lol:

Hey Dave, You can post on my thread. :mrgreen:

llf8ed wrote, "Where is your crankcase breather?"

It is number 1) lower back side of the left crankcase half.
It is pre Combat but I have a combat head, 36 mm Mikuni, 11/2 pipes, .030 compression plate.

pvisseriii said:

For the life of me I'm going to beat this dead horse till its gone to dust and floating in the wind.

I want a picture, or 4, in detail, showing the exact area and location of the oil pick up on a modified 1972 crankcase.......please.
Don't tell me to go here or there. If ever I can return such a demanding favor, I will GLADELY return it. Even if that mean sutting the hell up. I will......for a while anyway.

Click to expand...

I do not like to remove the baffle on the drive side as it helps to keep the crank rotation from forcing oil up the breather hole.


windy

bill said:

I do not like to remove the baffle on the drive side as it helps to keep the crank rotation from forcing oil up the breather hole.


windy

Click to expand...

Did you leave you forward pick up intact or did you plug it relying on the drilled out rear and baffle area for all oil pickup?
What has been your experience after this mod?

This seem to make some sence of it all, knowing that the problem is with the forward locate oil pick.
It is also my contention that if oil is kept from going up the breather, crank pressure could stablize without the need of inline devices. I think that pushing 50w oil up past the screens and foam in the breather port much less a reed or flapper valve beyond, has to increase crank pressure. We seem to slap in a new seal, add a check valve and think we have the answer.

What you take? Have people tried to dispell your ideas?

Peter

pvisseriii said:

bill said:

I do not like to remove the baffle on the drive side as it helps to keep the crank rotation from forcing oil up the breather hole.


windy

Click to expand...

Did you leave you forward pick up intact or did you plug it relying on the drilled out rear and baffle area for all oil pickup?
What has been your experience after this mod?

This seem to make some sence of it all, knowing that the problem is with the forward locate oil pick.
It is also my contention that if oil is kept from going up the breather, crank pressure could stablize without the need of inline devices. I think that pushing 50w oil up past the screens and foam in the breather port much less a reed or flapper valve beyond, has to increase crank pressure. We seem to slap in a new seal, add a check valve and think we have the answer.

What you take? Have people tried to dispell your ideas?

Peter

Click to expand...

I plug the front pickup and rely on the new rear pickup holes only. the small holes are .109 so as to act as a screen. IMHO the less oil in the breather the easier it is for air to move so less crankcase pressure and a reed valve would help even more to lower crankcase pressure. a good reed valve will take almost no pressure to open verses trying to push air ( and possably oil ) through the foam and screens in the original 72 breather. I ride mine anywhere from 150 to 650 miles at a time at 4000 plus rpm with NO issues in 25,000 miles.


windy

Peter, I can't speak for Windy but I would like to add a little more. People seem to wonder why the modification is being done, This is my understanding. When the motor is run at high rpm the oil seems to pool at the rear of the bottom end, This in turn pushes the oil back thru the breather hose which is not a very good because it can't make its way back easily then the crankcase pressure builds. This is because it has a hard time making its way thru the stock set up. I think this is why many have blanked off the rear breather and copied the 850 design. (thru the timing chest) The one way valve has been proven to help with leaks, This is not just a theory it has been proven. Of late there has been discussion of the method Jim Comstock has designed which has gone back to the crankcase for breathing, He has a reed valve on the back of the crankcase and blanks off the timing chest to air flow. This gives a smaller area for the air to exit the crankcase as it doesn't have to move thru the timing chest. When I did the old style mod to the cases I just wanted to be sure the motor never starved for oil, Also I wanted a motor that would not build pressure and in turn leak oil. I wonder if some people think they have oil leaks because of crankcase pressure when it may be they wet sump so bad at start up it pushes some of that oil past the seals. Of late some may have mixed up the two, Both can cause leaks in an old motor. If you do some searches on the forum you will find a lot of info that will shed some light on the subject, I am very happy with the set up I chose and have ridden my bike hard and not only don't have any leaks but the oil seems to return very good. I hope this helps.