I recently picked up an 85 K100, in reasonably good cosmetic nick, but I'm starting to come up with a bit of a list of minor issues that the bike has.

First off, fuel continues to drip from the forward line (return line) of the fuel tank when the hoses are removed. To be honest, I don't know the purpose of the return line, or where it's routed, but my other concern is it would appear that gas is getting into the crankcase, as the oil level has risen to the top of the sight glass when I left it closer to the bottom line last oil change. It doesn't smell terrifically gassy, but there is more stuff in there than there was.

With my other bikes, I'd just add an inline fuel shut off, or replace the petcock, but all this injector stuff is new to me and I don't want to cock it up.

Any advice would be much appreciated.

Josh

If the diaphragm of the pressure regulator is broken fuel will pass from there to #4 throttle body and into the cylinder and then to the crankcase.
I would say the first thing you need to do is a complete rebuild of the fuel injection. Don't run and hide what usually needs doing is cleaning and reseating connections and renewing hoses and in your case possibly the new Fuel Pressure Regulator.
Remove all the FI stuff and start with reseating and inspecting the manifold stubs as they crack with age and leak under the seat against the head then check that all the connections above the throttle bodies are airtight, work through the system and renew and replace as needed as time will have taken it's toll. Also the crankcase breather Z shaped hose from plenum chamber to crankcase will be cactus for sure as they rarely last past 5 years.
The drip is common and most here put a short length of fuel line from inlet to outlet after removing the hoses.

Thanks very much for the quick reply!

Ya, the z shaped hose is pooched, and will be replaced, which will hopefully cure the inconsistent idle and hesitation off idle. 

The regulator appears to be down by the throttle bodies. Does it control the shut off for allowing fuel out of the tank? I'm just curious as to why fuel could be leaking into the crank when the motor is off. I suppose it's possibly just the fuel left in the system that's dumping into number 4 every time the bike is shut down?

Thanks again

j

See if you can blow through the vacuum tube, not compressed air, or if you're game suck If it is leaking there be careful not to try to start with a cylinder full of fuel as it doesn't compress but conrods bend.
Usually there doesn't need a shut-off valve in the system and I have never seen one that does need it.
On the portal page there is a link to a site "so you just bought a BMW what now" he gives a very good run down on the things you are likely to encounter and fixes for a lot of it. It's a good read regardless.

sounds good. Thanks for the advice:D

Be aware that putting on that lovely z hose can cause you to use certain words.

Don't get put off or disheartened mate, I'm hopeless with this stuff and yet have been talked through some incredibly technical looking stuff, including all the things Rick mentioned here. If in doubt, keep asking and wisdom will be yours.
welcome by the way.
RT

ainsjac wrote:Be aware that putting on that lovely z hose can cause you to use certain words.

Smear a bit of silicon grease on both ends, then put the crankcase end on first followed by the plenum chamber end. They seem to go on fairly easy if done that way. Okay, so I've only replaced two!

RicK G wrote:See if you can blow through the vacuum tube, not compressed air, or if you're game suck If it is leaking there be careful not to try to start with a cylinder full of fuel as it doesn't compress but conrods bend.
Usually there doesn't need a shut-off valve in the system and I have never seen one that does need it.
On the portal page there is a link to a site "so you just bought a BMW what now" he gives a very good run down on the things you are likely to encounter and fixes for a lot of it. It's a good read regardless.

So I tried to blow through the vacuum tube, but I certainly can't. Does this suggest the fuel pressure regulator is working properly?

Forgive my ignorance, but is the forward fuel line connection on the tank, the return line, actually getting surplus fuel pushed up it from the regulator? For example, if I were to disconnect it when the bike was running, there's a possibility of fuel squirting out of the end of the hose, rather than the tank.

Here are a few more symptoms I should add about my problem of what appears to be fuel in the crankcase.

Lately, occasional hard starts. Crank and crank, open the throttle about half, and it starts up angrily. Similar to what I would consider a flooded carbureted engine. Hopefully I haven't bent any con rods! Once started runs well at mid rpm, idle is a little spotty, but I'm going to assume that's due to the z hose. Pulls like a freight train.

Today pulled the plugs, all look fantastic, tan and clean. Except for the plug threads, which are very oily, and possibly gassy. This adds to my theory that fuel is somehow leaking into the cylinders when the motor is shut down.

Any other bench tests I can do for the pressure regulator? The bike is in my basement, and I keep the fuel tank off, and outside so I'd rather not start it up.

Thanks again everyone.

The front line is the return line. The system keeps a constant pressure by way of the Fuel Pressure Regulator, it returns unneeded fuel back to the tank. There are only two ways raw fuel can get into a cylinder, bad diaphragm in the FPR (which by not being able to blow through it rules it out) and bad injectors i.e. pintle valve not sealing. Usually this will make for rich running but it is possible to get larger quantities into the cylinders when stopped. Remove the fuel rail with injectors and leave the bike sit and monitor if there is a fuel discharge from one or more injectors.

RicK G wrote:.... and bad injectors i.e. pintle valve not sealing. Usually this will make for rich running but it is possible to get larger quantities into the cylinders when stopped. Remove the fuel rail with injectors and leave the bike sit and monitor if there is a fuel discharge from one or more injectors.

Yep, sounds like a leaking injector. This happened to me. Symptoms weren't as bad as yours Rustyb but when I pull the injectors to clean them I found one was leaking.

Lots of instructions on Youtube on how to clean injectors with a can of carby cleaner.
You will need to get an o-ring kit for each injector. Fuelmser part# ISK-0500AX from Repco $13 for a set of two. A kit consists of top and bottom o-rings, spacer, pintle cap and filter. Its all easy to do once you work it out.
Make sure you clean very well around your injectors before you pull them to prevent dirt getting into the head

You'll want to replace your engine oil before too long also if you've got fuel in there.

Cheers

Seems the logical diagnosis. I'll pull them out and have a look. Thanks for the parts link.

If you do find you have a faulty/dirty injector/s, alternatively, you could get them professionally cleaned at about $30 each. Or buy a new set if they're really bad. OEM injectors for the K are not readily available but there are some other options available. Do a forum/google search from the Forum tab to find stuff we've already discussed about injectors but try this...
https://www.k100-forum.com/t9046-1-hole-vs-4-hole-injectors