Hi, so just got a 85 k100 and I’ve been reading around about the common “cold knocking engine sound” well, over the course of 2mweeks my idle has been terribly low on cold start and has got to the point I had to at least turn the idle screw to raise it to around 1.1k (did this tonight) so I don’t have to drive with the choke on....but before tonight , once the engine was warm I could leave choke off with almost no stall worry...
So far I’ve :
Changed the fuel filter,
Oil ,
Gear and final drive oil,
Adjusted free play in throttle ,
Cleaned the air filter,.
The engine knocking is so bad until I just jump on and drive and once warmed it runs great knocking is gone.
But...tonight (before raising idle speed) I had to give it gas to keep it running on a cold start......jumped on and it had tpower loss and some sputtering until I got it very warmed up (riding around)then all was good ...but with the choke not on it would stall (sometimes )at red lights ....point being the idle issue did get better but is getting worse again...
Oh and I started getting oil (not gear oil)leaking from the weep hole a week ago and it’s getting worst but not too bad..this bike is my only transportation and I just need it to last till winter when I can change seals and do a spline lube...oh and no slipping on clutch so I’m assuming oil isn’t getting to the clutch ...yet....so my questions are .....
1:Is that knocking really pretty “normal “ for k100’s and is that knocking even worse becuase my idle is so low at startup?
2: with the weep hole telling me about the seal needing changed do you think I could hold it off for about 6 months if it doesn’t make my clutch slip?
3: I know I gotta check the plugs(they were changed 2k miles ago and roughly a year ago by previous owner )but what else could be making my idle so bad(which makes that banging I hate worse on cold startup)?
I know this is very general...I will get more specific later ....just need some guidance , I’m very mechanically inclined but this is my first bmw and my first bike with 71k miles already on it...
Thank you

Idle speed when warm should be 1000 RPM plus or minus 50RPM. Does the noise reduce when you pull the clutch in? 2V bricks had a self diagnostic feature built in. With the bike warm and idling at 1000 RPM press the green starter button. The revs should stay the same or rise very slightly, if they rise the mixture is too lean if they drop the mixture is too rich.
Regards Martin.

I would be checking the rubbers as you may have a leak

Change the crankcase breather hose (11 15 1 460 480 Beemer Boneyard) as a start unless you know for certain it isn't old and in good health.  Oil coming out of the weep hole will likely require a new seal in the oil/water pump.  This is a rite of passage for new K owners I think.  Buy two seals (at least).  Third time was a charm for me with this particular job.

First off, are you talking about the weep hole between the engine and transmission or the hole between the oil and water pumps?  If it is the engine/tranny hole, you most likely need a clutch o-ring and possibly a rear seal.  They aren't all that hard to replace, with a helper, you can do them in a day, worst case, a weekend.  It is an excellent time to make sure the whole drive train is in good shape with clutch and drive shaft spline lubes, clutch boot, swing arm beariings, etc., etc. 

My first K bike needed the transmission grub screw tightened which is a similar job to getting to the o-ring and seal.  I was able to do the whole thing, which included splitting the transmission, from start to finish in seven hours with a lunch break.  We can help you plan the job so you have all the stuff you need at hand to make it as smooth as possible.  True, it's a bit of a big job, but these bikes really aren't that hard to work on.

A bad idle when cold could be a problem in the engine temperature sensor or it's wiring, but I would check the breather z-tube first.  In fact, if it didn't look brand new, I'd change it anyway because they seem to crack and leak pretty often.  There is plenty of information here on testing the temperature sensor so I won't post it here right now.

Ok , I’m going to go check the hose today...in fact ever since I pulled up the gas tank to get to the air box I have noticed the problem get worse so I need to double check the seal and check that hose...yeah I’m gonna do a whole drivetrain gearbox overhaul this winter,..oh yes the weep hole leak is under the transmission housing ...

If it's a rear seal issue then there's no real path for oil to foul the clutch.

If it's the clutch nut O-ring then it takes a while for the clutch to get oiled.

I once bought a K leaking from a bad O-ring and rode it 1,200 miles (to get it home) and the clutch did not get fouled.

I'd stick some paper towel or a cork in the weep hole (and drain it often) to keep too much oil from getting on the rear tire.

Also check to see if it's motor oil or gear oil coming from the weep hole. (Gear oil smells like sulphur.)

There's a seal at the back of the clutch pushrod and if that goes then gear oil can creep up the pushrod and come out of the weep hole.

So the crankcase breather hose has some small cracks

It’s motor oil for sure...

Guess you can’t see the small cracks in that pic....
Oh and it’s for sure motor oil coming out of the weep hole

Could I just duct tape the breather hose till the new one comes? I mean or just drive it till it comes without taping it(a lot of pulling stuff off just to tape it up for a week)
I’m going to order the breather hose now...

So should I have oil inside the breather hose? And there is a lot of oil everywhere ...the hose has crack but they don’t seem to go all the way thru to the inside , but I haven’t even checked the crankcase side...only pulled off the end to the intake area..
Took pictures ...oil right above the crankcase from unde air box...

Oh now I see fresh oil leaking from the end where the breather hose goes into crankcase...no wonder there is oil everywhere!

There seems to be a unusual amount of oil towards the front of the crankcase. Depending on the actual year (either 1984 or '85) that your 1985 was made your bike may or may not have the EPA emissions tubing/stub/nipple sitting in the front of the crankcase around the radiator shroud bottom. The stub may or may not be connected with rubber hose to a gray plastic check/relief valve sitting under the gas tank then connected to the gas tank vent.

Whether or not that emission stub could be slowly emitting oil if it is open is something to consider.
I'm working through similar issues myself with my '84.

That stub should be capped off. There is no need for the check/relief valve, you can remove it.
There's a service bulletin about it.

http://www.kforum-tech.com/Downloads/K100-service-bulletins-and%20special-tools/bulletins.htm

http://www.kforum-tech.com/Downloads/K100-service-bulletins-and%20special-tools/13%20014%2089%20%282228%29%2Epdf

You may also consider
1.Dirty injectors
2.Unbalanced throttle bodies
3.The 4-pin connector to the fuel pump should be checked, cleaned, manipulate the pins or sockets for better contact
4.The condition of the rubber fuel pump damper if the moto has been sitting

Ok so I didn’t find a valve , in the picture you posted the area where your valve is , is where my air box corner is.....there is a lot of oil directly below the area where the crankcase breather hose connects to the crank case .....and on the clamps that hold The plenum chamber to the intakes , i thinkmthey are called intake stubs? I just know on a lot of my past machines there is a clamp on each intake...
.well , there is a lot of oil around each intake and after I removed the breather hose from the plenum oil dripped a few drops from the plenum .thank you to everyone who reply’s and is helping me ....I’m a very technically inclined person and I haven’t had a bike (let alone a k bike ) in 5 years so please bear with me on the names of certain things...I’m re-learning as I go.....
To note , after tinkering with the breather hose and turning the idle adjustment screw up last night the machine is running a lot better.i have less vibration also ......but I really have the smell of gasoline when I come to lights or am sitting in traffic....like I’m running too rich...I haven’t checked the plugs yet and I really don’t notice a reduction in power....it’s hard to tell cuase I don’t like to beat on the bike and I never take each gear past 5k rpms ..but still a lot of power at the power bands...

You should probably try doing a plug chop. Type in spark plug chop reading and it should give you what is required, it is best done using new plugs after the bike has been warmed up. I try to do it at 60-70 MPH in 4th gear on a quiet road with room to pull over safely. I also like to do it with another vehicle shadowing me at a safe distance. What I do is find a quiet straight road with a place I can pull over and safely remove the plugs, then measure back at least a mile and do a run. Basically what you need to do is hold the bike at speed without varying for at least a mile. Then pull in the clutch while at the same time hit the kill switch  then roll to a stop with gentle braking at your selected pull over spot. Once stopped pull the plugs and do a colour reading, take pictures and post them if you are unsure of what you are observing. You should do a few practice runs to make sure have got the hang of it. If you aren't confident of doing this safely don't attempt it.
Regards Martin.

I would suggest checking the resistance of the engine temperature sensor both when the engine is cold(~2500 ohms) and when it's at operating temperature(~250-300 ohms)  if it is whack it can make the mixture either to lean at start or too rich at running temperature. 

You check it at the big connector on the Jetronic unit under the seat.  Don't know the pin numbers off the top of my head, maybe someone else can chime in with them.

Heresy23 wrote:Ok so I didn’t find a valve , in the picture you posted the area where your valve is , is where my air box corner is....I really have the smell of gasoline when I come to lights or am sitting in traffic....like I’m running too rich...

It's difficult for me to understand what you're describing. That breather stub tube in Volador's photo should be in the same location on your moto.

The photo shows a stub tube at the front of the engine that has an outlet into the crankcase. When a moto was sold in the US, that stub tube was connected to a hose running to the fuel tank. It was used to move vapor from the fuel tank to the crankcase. Connected in the middle of that hose run was a one-way valve blocking return of vapor to the tank. It was an invention to satisfy environmental ideologues in California when a moto was sold there.

Some owners have altered the system by capping that tube, attaching a hose from the tank vapor outlet then threading it through the frame so it extends toward the pavement behind the right foot peg. Other owners have installed what BMW calls an accumulator cup which receives both water drainage from the fuel cap and fuel excess or vapor. A hose is attached to that cup then routed behind the right foot peg. The engine might be running rich but you also might be smelling fuel vapor from the tank. Regardless, that tube into the crankcase should sealed.

More on "the Cup":

http://www.kbikeparts.com/classickbikes.com/ckb.tech/0.ckb.tech.files/thecup/thecup.htm

Regarding the check for the temperature sensor

"I would suggest checking the resistance of the engine temperature sensor both when the engine is cold(~2500 ohms) and when it's at operating temperature(~250-300 ohms)  if it is whack it can make the mixture either to lean at start or too rich at running temperature. 

You check it at the Jetronic Electronic Fuel Injection module under the gas tank.  Don't know the pin numbers off the top of my head, maybe someone else can chime in with them."

The resistance to check is between pins #1 (ground) and #10. Make use that you check the FEMALE PLUG and NOT the EFI module male pins!

You also really need to check that the stub is capped off as others have said. Your fresh oil picture on the right side of the motor in post #10, sure looks like the stub is open.

Thanx again , I’m going to do al of these checks to narrow it down but I still can’t fimd a stub. So I’m gonna take off the fairings later but just peaking they the right side this is all I see .. I was assuming it on the front right behind the fairing ..

I know I need to remove the fairing but I figured I throw these up... I’m looking in the correct area for the stub right ?

Sorry about too many pictures....so I was assuming it “should “ be here (where the arrow is pointing ) From the “stub” I had drawn to the corner I had also drawn is nothing ....
Sorry I haven’t been on my spelling ..lol..

And again thanks to all that posting,

It is tough to see. You may have to pull the right side fairing to see it.

Ohhh ok it’s behind the radiator in the front .. ! So how should I cap it (temporary) if it’s open? I’m dpsure I have some things in the garage to use to seal it off till I do what’s suggested...
I’m hoping I can take the fairings off and just stick my hand in there instead of removing the radiator .....

A golf tee or similar tapered shaped object into the tube works best.
Put a piece of hose over the tube, fold it over and zip tie it in place

If the tube is not present your moto was made before the EPA standards were required

I have a short length of hose, capped with a small hex head bolt screwed in the end of it. You don't have to remove the radiator to do this. The fairing and maybe the air box convoluted inlet pipe will be enough to get access.

Glenn

At least from all of the 85 US K100s I've seen the 85s don't have the pipe on the top front of the engine.

Ok update, I checked and found no stub tube, a lot of oil behind the raidiator though....so I’m gonna do a lot of these suggestions to figure out what is going on......needless to say until my bike gets warm it runs really bad and I must have the choke turned up until it reached operating temp....I did not replace the crankcase breather tube yet...that’s on order right now ....I’m going to check for any leaks in the fuel and intake system, just haven’t had the time recently and I need to take it apart and post some pictures....there is a lot of oil and grim around where the plenum is connected to the throttle butterfly assembly ....

Replace the three vacuum caps on the throttle bodies now too.  Those you can get at your local auto parts store for cheap.

Thanx ,Oh I was gonna throw those in my order becuase I have to make the 20$ minimum...if the vacuum caps are cracked will it effect performance?
Oh I just seen you wrote about getting them at auto parts store...rather do that .

So I replaced the 3 vacuum caps and there was another spot that needed a cap and now my idle is at least very steady and even!!

I too have had the fuel smell in similar situations,I found the" breather "UNDER THE TANK WAS KINKED fitted new pipe problem solved,hope it works for you.

Hi,

Had a thought this morning, are you sure that you didn't overfill with oil?

I would also be thinking now about changing all of the throttle body rubber tubes along with the rear breather tube.

Glenn

No, I mean I’m towards the high end of oil amount but not over the maximum...
Working on it all the throttle tubes now ....I noticed a lot of oil in the crankcase breather tube and dripping out of plenum when I removed it ...

glennpm wrote:Hi,

Had a thought this morning, are you sure that you didn't overfill with oil?

I would also be thinking now about changing all of the throttle body rubber tubes along with the rear breather tube.

Glenn

How many miles on the bike in question?  An '85 with low mileage and a lot of storage time is almost guaranteed to have rotten rubber bits all over the place.  There are also other problems waiting to pop up and annoy you, stuff like corroded electrical connections and plugged cooling passages.

My advice at this point is to do a bit of disassembly and removal of the air box and the air bushings to the throttle bodies.  Then a good inspection and replacement of anything with the slightest signs of cracking or rot.  It will make cleaning all the oil off easier and give you the opportunity to service the water temperature sensor, and all the electrical connections involved in making the engine run properly.

While you're in there, it would also be good to remove and clean the radiator thoroughly.  That will insure optimum cooling in hot weather.

You would be looking at a job that may take you anywhere from a weekend to a week, but the payback would be the knowledge that everything is up to snuff and will stay that way for a long time.

72k miles ..
Yeah, I really need to remove the air box and overhaul ....since this is my only vehicle and they made the air box such a pain to get out I gotta plan it out......love the fact that in this month I’ve only been getting nickel and dimed for repairs...3$ Heres 10$ there .......
Hey .75 can you give me some advice on this post?
https://www.k100-forum.com/t15097-what-is-this
Thanks!

Point-Seven-five wrote:How many miles on the bike in question?  An '85 with low mileage and a lot of storage time is almost guaranteed to have rotten rubber bits all over the place.  There are also other problems waiting to pop up and annoy you, stuff like corroded electrical connections and plugged cooling passages.

My advice at this point is to do a bit of disassembly and removal of the air box and the air bushings to the throttle bodies.  Then a good inspection and replacement of anything with the slightest signs of cracking or rot.  It will make cleaning all the oil off easier and give you the opportunity to service the water temperature sensor, and all the electrical connections involved in making the engine run properly.

While you're in there, it would also be good to remove and clean the radiator thoroughly.  That will insure optimum cooling in hot weather.

You would be looking at a job that may take you anywhere from a weekend to a week, but the payback would be the knowledge that everything is up to snuff and will stay that way for a long time.

https://www.k100-forum.com/t14705-tuning-my-k100

http://www.bmw-k100rt-page.eu/manual/Ignition/contentIgnition.htm

http://www.bmw-k100rt-page.eu/maintenance/contentMajorService.htm

Unless you have a clear maintenance history you need to start from the fuel tank down.

What is the inside of the fuel tank look like? Fuel level sender, Fuel Pump Rubber Damper condition?
Inside fuel tank hoses?

http://www.bmw-k100rt-page.eu/manual/FuelOil/6_FuelLub.htm

Fairing removal

http://www.bmw-k100rt-page.eu/manual/FrameForks/15_FrameForks.htm

1. Are spark plugs Bosch X5DC or NGK D7EA with spark plug 5KΩ wires

2. Check/clean with DE-oxit/reseat the ICU and ECU connector plugs

3. Check/adjust throttle position switch

http://www.bmw-k100rt-page.eu/manual/FuelOil/17_FuelLub.htm

4. Syncro throttle bodies

http://www.bmw-k100rt-page.eu/manual/FuelOil/17_FuelLub.htm

https://www.youtube.com/watch?v=gWCR3D8YMNs

5. Clean Injectors  Soak injectors in Lacquer Thinner many videos on cleaning injectors

6. Valve adjustment

https://www.youtube.com/watch?v=bFkPnLVkxWQ

7. check/clean the Temperature Sensor connector plug located behind the radiator

Good Luck with your moto