Since changing to synthetic oil, I have a large amount of oil leaking from the front/top of my engine. It is mostly spewing out the heat vents in the right lower fairing (RT), and some is pooling above the hall effect hatch and dribbling down the crank cover.

I removed the crank cover, timing chain cover and valve cover, and I removed and cleaned the gaskets and channels (both mechanically and with solvent) then siliconed them on each side of the gasket.

The sensor in the timing chain cover has an oil seal around the crank boss, but I noticed no oil inside there.

The oil is leaking at about a half a litre per 100km. Where could it be coming from?

you´ve mention the reason yourselfe:

syth oil is the problem - don´t feed the ol´K´s with that stuff

change to standard again- driving - change again & hope .... but I think it´s too late - for the old rubber seals

Maybe overfilled, but the main reason ist -as you can read in some threads for this case- the alien oil....

Take in warm regions one nice normal 20W50 oil without any additional stuff for motorcycles. One oil used for cars, bought in the DIY-market....

If you change all of the seals around the motor, from this moment on you can drive oil whatever you want..

I have already changed the rear main seal, but does anyone have a list of all the other seals on the engine? I didn't even know there was one on top?

There is NO seal on top

But the wind blowing the oil in corners you would never expect may irritate your eyes...

Clean it up perfectly, and check again after some kilometers, may be the top of the timingchaincover isn't fine yet, or the overflowhole from oil/waterpump shows some drops....

Hot oil can be very difficult to trace back to its source but if you really mean half a liter per 100 kilometers I would check to see if you forgot to replace the filler cap (or the O-ring on the filler cap !

I will re-do them and replace the seal inside the timing chain cover. Is it a standard (generic) part or must I buy original?

Buy original, and follow the mounting instructions for the new TFP-Seals.

Or buy one OEM-Seal in the right dimension and try again in one year

Hoechst, merci vilmal

I'm waving the BS flag on that claim. I run Mobil-1 15W50 car oil in both my '84 bricks and both are oil tight. Synthetic oils are not the cause of oil leaks.

Most of the K bikes except the earliest models have a vent tube from the top of the block to the underside of the fuel tank with an in line check valve so you don't get fuel in the oil. This tube is supposed to vent the gas tank to the crank case, preventing evaporative emissions from entering the atmosphere and making the hole in the ozone layer even bigger than it already is.
If that hose has aged from heat and cracked or separated it will allow crank case pressure to vent oil to the top of the engine and make a nice mess. I strongly suspect this is the problem. It is so out of the way, and attaches to the top of the block right under the radiator. No shortage of heat there, and a nice fan to blow the oil around. Just my guess. Keep us posted on the findings.

Themason,
Good to have you back. I have an 85K100RS and the breather tube is on the top of the block towards the rear of the engine and connects to the air intake plenum at the rear, without any check valve, but it also is subjected to high temps and if cracked or loose will spill oil onto top of engine, especially if over filled a little.

... and for sure causes a new filled synthetic oil a lot of leaking after a while. This modern stuff used with twenty year old seals gets out of your engine as soon as possible. We could give you one hundred names of users where it happend exactly like this. May be there are fifteen, who were as lucky as you.

As i wrote, if you examine your engine down to this and replace all seals, then your choice of oil is free.

Yes, agreed. I read on the old forum that changing to synthetic after many years of running regular oil can, and usually does cause oil seal failure.
TheMason must have been running synthetic on both bikes with low milage/age...that's why no leaky seals. OoB

That is a different breather hose. You should have both.

Would the vent from the fuel tank to the front of engine come from a nipple in the front of the fuel tank or further back. I have two nipples on my fuel tank, one points down and is about halfe way back and just right of center. The other points rearward and is on the right side about half way back both have tubes that run towards the rear of bike and vent to atmosphere behind the rear master cyclinder.
JohnC

No, no, that is a different tube. This is the fuel tank vent. The earliest '85's like mine and I suspect yours vented the tank down a hose on the right frame tube behind the right battery cover, down below the right foot peg plate. Later in 1985 when the 50-State bikes came out with flappers in the fuel filler, the tank was no longer vented to the atmosphere. Instead the vent hose exited in the same spot under the tank, but goes forward through a small one way valve (looks similar to some in-line fuel filters on carbureted bikes) and connects to the top of the block just under the radiator. This is the hose I suspect has either split of broken off allowing oil to escape from the crankcase.

No. One bike I have owned since 1984 was switched from a steady diet of Kendall GT-1 20W50 to Mobil-1 15W50 full synthetic at about the seventeen year point with over 150,000 miles on that engine. No leaks. Another old K-100 was switched to synthetic from dino oil at around 15,000 miles with no leaks ( this bike is the perfect original early K bike with only 22K miles total, my little museum piece ).
Same thing with a 1988 Audi. I bought it in 1993 with 53K on the odometer. The previous owner had been using some crap no-name 30 weight oil. I found a container of it in the trunk. Horrified, I immediately switched it to Mobil-1 and nothing leaked. Never has, and the car has 145,000 miles on it today. Completely oil tight. More recently I bought a 1993 Audi off a cousin with 160,000 miles on it. He used Castrol GT-1. I switched this car to Mobil-1 too, before I even rolled it off my cousin's driveway. No leaks.
You are perpetuating an old wives tale with no basis in fact.

I can confirm that: K1100RS 1996 with 90 000 km with unknown oil history switched to Castrol Edge 10W-60 - no leaks, no extra oil consumption. Friends K100RS running on Mobil 1 synthetic - no oil leaks.

Best regards,

What's the difference between 'crap no-name' oil and the expensive oils? Extra special top notch additives? Because the basis is the very same! Both get their oil from the same source and since the no-name company most likely will not have its own factory, it buys it from whom? Have a guess! They just put their stickers on it. And when it comes to newer, better, fancier additives: as a chemist my every day job is to fool people into believing that my extra bits I'm doing to the regular chemistry is the key to a happy life Let me tell you, it is not in most cases. Most of the time there is nothing new about it
That'S why I use the cheapest oil I can get hold of. Same reason why I don't put Shell V-Power in my tank and why I use Acetone as a brake cleaner instead of 'brake cleaner'