To put this in context, about 15,000 miles ago I had the bike apart for slingers and general inspection and new seals were installed in both units --Ted Porter did the work-- so to my thinking this leak shouldn't be happening. Looks like another bit of work faces me in the near future.
I guess I'm not really asking a question, but any thoughts will be appreciated.
The only way to know for sure would be to have some analysis done on the oil or to just go ahead and pull the transmission. Then you would know where it's coming from. I wonder in my case if the area that the seal rides on at the back of the crankshaft might not be a bit rough, thus causing the deterioration of the seal and the leak. It's something of a pain to remove the transmission, requiring serious torque to undo it. I'm thinking I'm going to just let it ride for now.
What about switching to a dino engine oil for a while? In the early days of synthetics, I had heard they didn't use the right seal-swelling compounds which resulted in a lot of leaks. Possibly a change might help your situation.
What's the engine compression...did you do a compression test or leakdown test? Have you had the top end redone? Could it be that you are getting some excess blowby if the rings are not seating or the gap is too wide? Excess blowby might also show as oil mist or vapors at the engine breather port at the front of the engine.
'78 R100/7 '69 R69S '52 R25/2
First post here, not sure if that's the right place to introduce myself... Anyway, I'm located in France and own a 1969 R60/2 since 1978. This is my 4th /2 bike, if I include the R26 which started it all.
This machine is a 12V alternator model, with Meier 24 liters tank and dual seat. I fitted stainless steel exhaust and pipes found in England, which you can tell just by the look of the pipes! Apart from this it is quite original.
I'm interested in this excess blowby thing, which my bike seems to suffer from. I redid most of the engine (bottom and top end) about 1800 miles ago. Since then I have the same oil leak Jon is talking about, plus one at the front, behind the alternator. Oil leaks from the engine breather too.
All in all that's not a major problem, and I guess I can live with it, but I'm curious to learn more about the excess blowby: where does it come from, and is there a possible cure? A simple one I mean! Thanks.
The way to check is to do a leakdown test. You can google that and find out what it is and possibly make one. I ended up buying a pretty decent device from Harbor Freight here in the US. Basically, what you're doing is bringing one of the cylinders to TDC on the compression stroke so that both valves are tightly closed...this is all with the engine NOT running. Then with a spark plug adapter, you plug into the cylinder and pressurize the chamber. A good leakdown tester will then tell you what the percentage of leakage is. If there's no leakage past the rings or valves/valve guides, then the percentage is 0. If it's going past the rings, it will some number which is calibrated to be the percentage of what's coming in through the spark plug hole. Around 5% is probably pretty decent...could even go down to near 10% and be sort of OK. The engine must be at or near operating temperature for this.
Without the measurement numbers, you can listen for where the air is leaking. If you go back to the exhaust pipes and hear air, it's the exhaust valves. If you pull off the carb for that cylinder and hear air, it's the intake valves. If you pull the oil dipstick and hear air, it's the rings.
That's the basics. This is something that should be done before a teardown in order to know what to look for during the teardown.
'78 R100/7 '69 R69S '52 R25/2
Next time, I think I'll get the fugitive oil off the tray with a syringe and put it alongside samples of Amsoil engine oil and transmission lube. That way, I should be able to tell which it is and decide how to go from there.
The bike had new rings when the slingers and seals were done, and the heads were rebuilt with new valves. That was at around 57,000 miles, and I just turned 73,000. Everything seems OK: smooth running, good compression, good performance, and zero smoke. So I don't think I have any real engine problems. I get a little oily residue around the breather port, but never enough to suggest any real issue.
Now I'll have to wait until enough accumulates on the tray that I can finally determine which it is. My strong hunch at this point is that it is engine oil, in which case I'll just keep an eye on the levels and leave things be for now.
- amsoil_samples2.jpg (124.87 KiB) Viewed 391 times