`71 R75/5 oil drip from driveshaft boot

[chefnation]

Greetings, just bought a beautiful /5. couple things I'm seeing after a ride.
small amount of gear oil drip on boot. that should be dry inside boot right? indicates leaky seal in there?
also, oil seeped out of carb air intake ran down to carb on right side.(first ride) this appears to have stopped.
today went for 20 mile ride. shut bike off, shut petcocks off, put on center stand. small amount of fuel leaked out of both carbs
has the larger oil pan (4 QT) oil level is ok. Jim

 

[20774]

Welcome to the forum! Actually there is oil inside the driveshaft to the tune of 100cc for the earlier models. Its purpose is to slosh back and forth when you accelerate and brake. It will lube the front u-joint as well as the splines at the aft end of the shaft. If you driveshaft has an usual alignment such that the back end is somehow higher than the front, the oil will pool up front.

As for the leak, you should check that the clamps around the boot front and rear are tight. If still leaking, then I would consider draining the driveshaft fluid and see how much comes out. As I said, I think it is 100cc. Then put 100cc back in.

Yes there might be some oily issues on the right carb. The crankcase breather valve dumps any misting oil into the right carb. Note that a too high oil level could contribute to that. You have a deep pan...takes 4 quarts/liters? That's an awful lot of oil...I don't recall a deep pan taking that much. Do you have any idea who makes it? Any pictures so we could see?

 

[stevenrankin]

Boot

One other thing about the boot between the swing arm and transmission is they do get old and crack over time. LOL, if it is the original boot, it may be time to replace it.

As to the fuel leaking when parked, it could just be a booger in the float needles or, perhaps the floats themselves need changing? Again, it depends on age, floats don't last forever and the original floats don't play well with ethanol mixed fuel if you are using it.

Four quarts? To be honest, I have never seen a four quart oil pan on any BMW airhead. As Kurt says, check it out, send pictures but I can tell you if you are overfilling, you will get oil forced out into the carbs. There will always be a bit of oil mist going into the carb, excessive amounts may mean other problems. LOL, check first the amount you need to fill then worry if the problem doesn't stop.

Enjoy the riding. St.

 

[chefnation]

One other thing about the boot between the swing arm and transmission is they do get old and crack over time. LOL, if it is the original boot, it may be time to replace it.

As to the fuel leaking when parked, it could just be a booger in the float needles or, perhaps the floats themselves need changing? Again, it depends on age, floats don't last forever and the original floats don't play well with ethanol mixed fuel if you are using it.

Four quarts? To be honest, I have never seen a four quart oil pan on any BMW airhead. As Kurt says, check it out, send pictures but I can tell you if you are overfilling, you will get oil forced out into the carbs. There will always be a bit of oil mist going into the carb, excessive amounts may mean other problems. LOL, check first the amount you need to fill then worry if the problem doesn't stop.

Enjoy the riding. St.

 

[stevenrankin]

Deep

Well, I will say that is a deep pan!. LOL, it looks like the center stand is almost rubbing it. It doesn't ring a bell as to how much oil it should hold. Check out this site and see if anything makes sense. http://largiader.com/tech/oilpan/

Three quarts is still my guess to be the amount needed. Are you certain you have the extended pick up on the oil pump? St.

 

[20774]

Well, I will say that is a deep pan!.

Wowser!! That's deep!

 

[stevenrankin]

Another link

https://bmwmotorcycletech.info/oilingsystem.htm. St

 

[20774]

I think the pan is a MAC deep sump or similar. Anton has a picture on his page of something similar by MAC. I haven't been able to find specifics but it seems like the pan support 3.5 quarts.

I found an old ad by Dytonis Inc out of New Jersey. The ad doesn't have very good pictures but it mentions in the text that it increases oil capacity to 4 liters.

 

[melville]

I think the pan is a MAC deep sump or similar. Anton has a picture on his page of something similar by MAC. I haven't been able to find specifics but it seems like the pan support 3.5 quarts.

I found an old ad by Dytonis Inc out of New Jersey. The ad doesn't have very good pictures but it mentions in the text that it increases oil capacity to 4 liters.

Yes, that's a MAC pan. I have them on two of my bikes. Put 3 quarts in it and the dipstick should show about 1/2 quart low. That's PERFECT!!! You'll have both more oil than stock available AND you'll reduce peak pressures in the crankcase as the pistons move in and out.

 

[chefnation]

thanks Melville.

so 3.5 qts and you run yours like that? previous owner kept it to max fill line. 4qts.
3.5 better? Jim

 

[bluehole]

Don't want to confuse the issue, but I have a deep pan too and I put in about 3 quarts. You may have to do some experimenting.

 

[melville]

so 3.5 qts and you run yours like that? previous owner kept it to max fill line. 4qts.
3.5 better? Jim

Mine shows 1/2 qt low with three quarts, but yes, run it where it's 1/2 qt low. My bikes will need that 1/2 qt replaced (gets to 1 qt low on the 'stick) in 1000 to 2000 miles. Which is about the same oil consumption as my BMW car.

 

[Na Cl K9]

Crankcase volume/drive shaft lubrication…

A deep oil pan serves two functions. The added surface area provided by the large casting improves heat transfer and cooling efficiency. This is a good thing since more oil means more accumulated heat to remove. This is the law of deminishing returns in action. Secondly, the older /5-/6 engines had a crankcase volume issue such that when over filled they would rapidly send the excess out through the breather and into the right hand carb intake. (/2’s just dumped it on the road). The problem was very noticeable with the first R90/6. The R90/6 would blow out enough oil after topping up to the line that after 50 miles or so the oil level dropped by a quarter inch on the dip stick. A factory service bulletin suggests scribing a new max mark at that point. /7 motors came with a deeper pan which resolved the volume issue. So, as noted by previous posters. Filling to a half quart low (3.5 quarts) in your pan improves crankcase volume, reducing venting of excess oil to the carb, reducing excessive heat retention in the volume of oil present. Now, about your driveshaft boot. Check the oil level in your shaft housing- 100cc’s is correct. Clean the boot and and clamp area thoroughly and dry. Ride the bike and find the source of the leak. Tighten clamps or replace boot. As the shaft spins, oil is drawn up along the shaft to the u-joint where it lubricates the joint, is thrown off, is accumulated in the boot and drains back to the bell where the process is repeated.

 

[chefnation]

A deep oil pan serves two functions. The added surface area provided by the large casting improves heat transfer and cooling efficiency. This is a good thing since more oil means more accumulated heat to remove. This is the law of deminishing returns in action. Secondly, the older /5-/6 engines had a crankcase volume issue such that when over filled they would rapidly send the excess out through the breather and into the right hand carb intake. (/2’s just dumped it on the road). The problem was very noticeable with the first R90/6. The R90/6 would blow out enough oil after topping up to the line that after 50 miles or so the oil level dropped by a quarter inch on the dip stick. A factory service bulletin suggests scribing a new max mark at that point. /7 motors came with a deeper pan which resolved the volume issue. So, as noted by previous posters. Filling to a half quart low (3.5 quarts) in your pan improves crankcase volume, reducing venting of excess oil to the carb, reducing excessive heat retention in the volume of oil present. Now, about your driveshaft boot. Check the oil level in your shaft housing- 100cc’s is correct. Clean the boot and and clamp area thoroughly and dry. Ride the bike and find the source of the leak. Tighten clamps or replace boot. As the shaft spins, oil is drawn up along the shaft to the u-joint where it lubricates the joint, is thrown off, is accumulated in the boot and drains back to the bell where the process is repeated.

Thanks John D`oh, she's just below max fill level now. Oil has not blown out of air intake since that first long ride.(50 miles). Does it stress seals etc.to just run it like that ? its fresh oil. bike will get put away probably mid December.(salt flies)I could dump a pint I guess.

 

[Na Cl K9]

Thanks John D`oh, she's just below max fill level now. Oil has not blown out of air intake since that first long ride.(50 miles). Does it stress seals etc.to just run it like that ? its fresh oil. bike will get put away probably mid December.(salt flies)I could dump a pint I guess.

Pressure in the crankcase is modified by the relief function of the vent. Your engine seals will survive everything but age and full synthetic oil. All but the rear main are double lip style. Trying to let a little oil out the drain is really not practical. Just wait till the next change. I’d be curious how far the oil pickup extends into that oil pan you have.

 

[chefnation]

Pressure in the crankcase is modified by the relief function of the vent. Your engine seals will survive everything but age and full synthetic oil. All but the rear main are double lip style. Trying to let a little oil out the drain is really not practical. Just wait till the next change. I’d be curious how far the oil pickup extends into that oil pan you have.

Previous owner had bike 8 years. He bought it with Mac pan installed. He changed pan gasket fairly recently. I’ll ask him if he knows. Gasket still a little wet here and there. Nothing major. He said he put 15-40 rotella regular oil