K11 Owners Group

[rederic]

Hi,
requesting advice from all you K11 experts out there.

I've a '92 RS. It has recently developed a very poor 'lumpy' idle which often results in the bike stalling. However once you raise the revs a few hundred it seems to smooth out- that is until you reach around 3,500 revs when it becomes rough/vibey. These vibes seem to increase the faster you go.

Has anyone else experienced this? Any suggestions would be appreciated before I start taking things to bits.
Cheers, Mick

[joeangi]

Sounds like a vacuum leak to me, I don't know where to tell you to look first. Look around for a cracked hose.

Joe
_________________
1994 K1100RS
1986 K100RS

[Ted]

First stop is the crankcase breather hose, those suckers go bad every few years and the symptoms are exactly as you describe. If not that the great hunt is on
_________________
Ted
KOG#1

[Flying Duck]

If it's not the CBH then spray some starter fluid around the boots between the throttle bodies and the cylinder head. Those can get old and leak.
_________________
93 LT (x2)
94 RS
86-97 K75F(K75/100/1100 Frankenbrick)
86 K75C w/paralever, hi perf cams,TURBO!
91 & 92 K75Ss
91 K1
86 custom K100
14 WR250R
IBA #17739 (SS1K, BBG, 50CC)
Buy parts HERE

[Ted]

Unfortunately with an air leak it can be a lot of places. The issue is that unmetered air is getting in to the system somewhere so while the bike thinks it is giving the right amount of fuel for the air entering, it is actually running lean (and resulting in poor idle and top end performance.)

One thing to remember, you might have multiple air leaks, none of them alone noticeable but all together a problem. If you are going to take the time to really look, don't just stop if you find one. Being mindful that I may confuse an e30 BMW with a BMW Motorcycle as I have had to chase down leaks in both, the very basic path of air to exhaust is:

Here is the engine...



Notice the air filter/VAF sensor box on top to the left, the air collector on top to the right, the throttle bodies under the air collector, and the engine underneath that.

Step 1. From the air box/filter/volume air flow sensor (inside) where the engine measures the amount of air to match to fuel, to the air collector (below). Everything from the VAF in the air filter box on, including the engine, is considered "metered air" and any leaks will cause problems.

VAF Sensor (#8 below) inside the air filter box:



Collector:



Step 2. From the Collector metered air passes through rubber collars (seen above in the collector photo - the left one is a K100 the right for a K75) to the throttle bodies where the air is mixed with gasoline, then through another set of rubber collars to the engine cylinder head.

Throttle bodies:



Step 3. In the cylinder head the gas/air mixture is burned to power the engine, and the exhaust is ported out through the exhaust pipes.

Any leaks in this chain, or in the engine, will cause an unmetered air leak.

The method is simple but time-consuming...

First - usual disclaimers, this is what I do but seek independent verification and if you are not comfortable doing this, take it to a shop.

DO NOT DO THIS IN AN ENCLOSED SPACE. I use Fi-Safe starter spray which is quite flammable so I do it outside preferably in a breeze. One can also try WD-40, but I don't think that works very well. Know where the alternator is and do not spray anywhere near it!

The technique I use is to give various locations a quick spritz and listen to hear if the idle changes, speeds up or slows down, in response. If I do come across this, I've located an unmetered air leak.

1. The crank case breather hose is a likely culprit because it often develops cracks around the hose clamps. I would probably replace it anyway if it hasn't been done in a year or two as it will eventually go bad. You should also check the o-ring around the oil fill cap, these also go bad over time and allow in unmetered air. Both of these are things you should probably do anyway and as the cost is under $20 you might want to go ahead and just order the parts. One note, be very careful of the hose clamp end when installing the new breather hose, careless placement of this may cause the clamp tail to abraid the wiring loom coming down the frame rail causing all kinds of electrical grief.

Second place I check is the rubber collars between the throttle bodies and the engine, both from the air plenum to the throttles and from the throttles to the engine. This is where (outside and in a breeze) I can give the rubber bits quick spritzes, waiting for the previous spritz to dissipate before giving the next, with the bike idling and listen for any change in idle speed. I make sure to get a red straw to put into the spray nozzle so I can be precise in where I am spritzing.

Third, I check the air box/collector connection - rare to find a leak here but not unheard of.

Like I said, it is time consuming work but after 15 and 20 years, these leaks definitely do not go away.

If you find leaks, and hopefully it is the easy and most common breather hose or cap o-ring, it is simply a matter of taking apart, replacing, and putting back together.
_________________
Ted
KOG#1

[Flying Duck]

WD-40 is no longer flammable. Either the safety Nazis got to them or there was a lawsuit. It still says flammable on the can but I've tried lighting both a puddle and spray from the can of newer WD-40 and nothing happens. The old stuff was though. I've got cans of both. One makes a great torch, the other, no joy.
_________________
93 LT (x2)
94 RS
86-97 K75F(K75/100/1100 Frankenbrick)
86 K75C w/paralever, hi perf cams,TURBO!
91 & 92 K75Ss
91 K1
86 custom K100
14 WR250R
IBA #17739 (SS1K, BBG, 50CC)
Buy parts HERE

[Ted]

[Stoked Steve]

Great write up on locating air leaks, Ted. This ought to be a sticky in the tech section.
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Steve
Virginia Beach, VA
93 K1100RS Mystic Red SOLD
12 Suzuki DL650A VStrom

[Rafal]

Hello there!
Nicely done Ted! Yet one remark. 1992 RS means that it is either K100 16V or K1100 - both with Motronic ECU. The diagram that You have presented are for LE-Jetronic - 2V bricks.





There is no air flow meter. Only air temperature sensor and throttle position sensor. Also there is no connection between TBs and fuel pressure regulation system. Yet there is an additional rail behind the TBs, and hose from airbox to timing chain cover.
There is no rubber connector between TB and engine head, only o-ring. Airbox top cover is connected to TB via bend hoses, but I don't recall the situation when they got damaged.

Best regards,
_________________
Rafal
K1100RS is a real beast (in Marrakesh Red)
K75S is a real beauty - she has gone , but not to far .

[rederic]

Wow,
don't know what to say but thanks everyone for the fantastic response.
I've now printed them off, ordered new breather and cap o ring and I'm ready to persevere/skin my knuckles/curse the tiny spaces you have to work in/wish I had baby fingers.
Looking forward to getting the old thing up and running properly again in time for my run up into the Scottish highlands.
thanks everybody, Mick

[Scott_Anderson]

Just read in another post about rough running caused by a bad O-2 sensor. Yours may or may not have one being non-US.
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Ride safe.



1995 K1100LT 0302044
2017 FLHTK Ultra Limited
Garmin StreetPilot 2820
Garmin Zumo 550
Garmin Zumo XT
"One who does not ask questions is ashamed to learn" Danish proverb
1997 K1100LT 0302488(R.I.P.)
1997 R1100RT ZC62149(sold)

[Ted]

Thanks for the clarifications Rafal - guess with my new bike I have 8v on the mind
_________________
Ted
KOG#1