Oil leak

[dfang]

Hi guys,finally got the bike on the road and there is oil on the shelf under the engine ,put a new seal in main and oil pump,ran engine using cooling fans prior to reassembly,no oil leaks spotted by two pairs of eyes,yet I am back to square one again.any help would be greatly appreciated.

[Bob_Roller]

Did you have the oil leak before replacing the main seal ??

[dfang]

Yes,hence the reason for replacement

[Bob_Roller]

The only thing I have heard about with main seal leakage after replacement, was the cap that goes over the end of the crankshft where the seal contacts it .Ii guess it can develop wear and cause leakage or seepage .
No idea how common this is .
The other thing that I have experienced, is when I went from semi synthetic oil Spectro brand, to full synthetic oil Mobil 1 .
I got a main seal leak, replaced the seal and the leak started again, went back to the semi synthetic oil and the leak stopped in a short period of use .

[dfang]

I’m using mineral oil,as bmw has stipulated,anyway back to the drawing board,I will take bike to local mechanic to check out.

[Steve]

I kept replacing the rear main seal, and it kept leaking, until I realized that I had the wrong dip stick in place and I was putting too much oil in. Problem solved! There are two dipsticks, one for the earlier sump and one for the later, deeper sump.

[dfang]

Thanks for your replies guys,I have the deep sump,so maybe too much oil,I will also have engine breather looked at in case of blockage.

[Bob_Roller]

Are these OEM oil sumps, or aftermarket?

[georgesgiralt]

Hi !
If I'm not mistaken Anton Largiader has a comprehensive article on the stick length and application.

[dfang]

Have checked the dip stick,appears to be the right one for the model.if I pull gearbox off to check,what rpm’s should I run it at to get pressure up, to hopefully spot the problem.

[Barry]

Airheads have a powerful high volume oil pump. When cold the oil pressure will be close to maximum at idle and when warm you shouldn't have to go much above 2000 RPM.  The oil pressure relief valve discharges at 75 PSI over the timing chain and you will often read that the engine should be kept above 2000 RPM to ensure good lubrication of the chain.

[dfang]

So I have decided to remove gearbox,so hopefully I can see where the leak is coming from.is it safe just to remove the clutch assembly,and run the bike with only the clutch carrier/flywheel in place.

[georgesgiralt]

Hello,
Did you, when you exchanged the seal, previously, thoroughly clean the place ?  And was a lot of grunge present when you started ?
Did you touch at the oil pump at all ?
Because, here, you have two places where oil can leak. Obviously the main seal and the oil pump.
Maybe, and this is just a thought, old grunge and mud sealed a leak at the oil pump cover. And once cleaned up started leaking.
Regarding the tracing of the leak, may I remind you of the old method ?
Clean properly, then apply some talcum and then run the engine. Oil if there is oil will bond to the talcum making it's path more visible.
As per removing the gearbox, !, for one will favor the engine displacement method in order to have the bike on it's wheels (as you plan to run it at idle without the gearbox).
This goes as follow :
Disconnect the pipes and the gearbox from the engine and swing arm.
Put a wooden box and a scissor jack under the engine, then remove the engine mounting stubs and advance the engine as far as it will go.
Disconnect the gearbox and remove it.
Put the engine back in place and insert the two stubs.
I've had to use this method a couple of times. It is efficient and fast. (well faster) and leave the bike stable on it's wheels. Handy if you have to wait for parts or analyse a gearbox problem which takes time...
I _do_ hope this helps.
Chin up, you'll find the problem and solve it !

[dfang]

Both main seal and oil pump o ring replaced,rear of engine cleaned spotless,have had bike to mechanic to check engine pressure release valve,he states it appears to be working ok.bike was a barn find which hadn’t been running for 20 years,should I replace pressure relief valve as step in the process of trying to sort this problem out.

[Barry]

Both main seal and oil pump o ring replaced,rear of engine cleaned spotless,have had bike to mechanic to check engine pressure release valve,he states it appears to be working ok.bike was a barn find which hadn’t been running for 20 years,should I replace pressure relief valve as step in the process of trying to sort this problem out.

I'd find out where the oil is coming from first.

The oil pressure switch is a common cause of leaks and the oil can be blown backwards when riding.  If you haven't already done so I'd clean the area around the switch and see if it stays clean in use.