Author Topic: '94 K75S Appropriate AFM screw position  (Read 422 times)

Offline 1ockdown

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'94 K75S Appropriate AFM screw position
« on: October 06, 2019, 05:43:40 PM »
The AFM screw I'm talking about is the screw under the little rubber cap on top of the air box. Forgive me if I misnamed it.

I recently bought a '94 K75S with 9,000 miles on it, yes Nine Thousand, for $300. It was one of those bikes they used for filming movies and marathons, like Boston Marathon, or Spike Lees Klansman, trailered to and from events. From what I've been told the bike was only ridden by contracted California state highway patrol, and all maintenance done at dealerships. I'm converting it to one of those cafe/scrambler monsters.

I've been having issues with my bike running rich and went on a search to find the culprit. All fuel lines replaced, Intake boots between plenum and TB's replaced, vacuum lines replaced, Crank Hose replaced, all filters changed, oil changed, clutch properly adjusted with proper free-play, TPS adjusted. I've ruled out Fuel Pump and Fuel Pressure regulator for now, since there's 9K miles on the bike, and last time it was inspected was 2016, and it was supposedly serviced regularly at BMW dealerships.

When I first got the bike, it hesitated really bad when quickly snapping the throttle, even just died out sometimes. Idle was all over the place, I read all the forum posts where people were having that hesitation symptom and fixed things accordingly; TB boots were cracked, fuel lines cracked, Crank hose cracked.

Now it does not die out anymore, however it may unless it's fully warmed up. The other day I adjusted the Brass idle screws on TB's with vacuum gauges to get my idle proper. Today I looked at the AFM screw I mentioned above because when I hit the starter button while the bike was running, RPM's dropped. It was 1/4 Counter-clock wise turns from fully clockwise. AKA i screwed it 1/4 CW till it bottomed out.

I then progressively unscrewed 1/4 turn at a time until RPM's stayed the same when I hit the green starter button. I ended up with 3-3.5 CCW turns from fully bottomed out.

Fully warmed up it idles nicely at 1000-1100 RPM's, but still chugs-clunkers a tad when I crank the throttle off idle, and first gear feels underwhelming compared to the other gears; First Doesn't nearly pull as hard as second or third.

My question currently is how far out is that screw supposed to be? If there's anything else in my description that peeks your interest, I'd love to hear it.

Pics of before and current attached.
  • My garage in New York
  • 1994 K75S ABS

Offline johnny

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Re: '94 K75S Appropriate AFM screw position
« Reply #1 on: October 06, 2019, 05:51:42 PM »
greetings...

all this moto needs is back to back to back to back tanks of no corn ethyl and a bottle of marvel mystery oil in 1st 2 tanks and a bottle of techron in each additional tank... a thousand miles worth... not 1 mile less...

put all you adjusted back to oe and give it the fuel and miles it wants... after a thousand miles sync the injectors and you are done... needs nothing else...

you mean this screw... if so that only affects idle... from full in it shoild be out 4 turns for oe...


* filterhus.JPG (45.18 kB . 747x562 - viewed 60 times)

j o
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Offline 1ockdown

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Re: '94 K75S Appropriate AFM screw position
« Reply #2 on: October 06, 2019, 05:56:46 PM »
johnny, I know the AFM screw has been touched before because when i popped the rubber thing off, it had been misshaped like someone tried to jam it back in there.
  • My garage in New York
  • 1994 K75S ABS

Online Chaos

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Re: '94 K75S Appropriate AFM screw position
« Reply #3 on: October 06, 2019, 06:07:28 PM »
I'm converting it to one of those cafe/scrambler monsters.



Why?  You'll loose the versatility of a K bike, one of their best features. 
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1987 K75S    VIN 0231
Original owner, Original litter
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Offline 1ockdown

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Re: '94 K75S Appropriate AFM screw position
« Reply #4 on: October 06, 2019, 06:10:32 PM »
Johnny, 2 gas tanks full of mystery oil, then techron in each tank, dont mix the two together right?

Chaos, I wanted a project, and I was able to get this bike cheap enough to accomplish that. I'm not sure which versatility's you're regarding, but the most I'm going to be doing beyond what you see now is a new seat and looking into new gauges.
  • My garage in New York
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Offline johnny

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Re: '94 K75S Appropriate AFM screw position
« Reply #5 on: October 06, 2019, 06:14:59 PM »
greetings...

look... all way in then out 4 turns...

1st tank 1 bottle of marvel mystery oil...

2nd tank 1 bottle of marvel mystery oil...

3rd tank 1 bottle of techron...

4th tank 1 bottle of techron...

5th tank straight no corn ethyl...

do this in 1 day or 2 continous days...

injector sync..

ride it... needs miles...

j o
  • :johnny i parks my 96 eleven hundert rs motobrick in dodge county cheezconsin  :johnny

Offline 1ockdown

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Re: '94 K75S Appropriate AFM screw position
« Reply #6 on: October 06, 2019, 06:16:59 PM »
Roger that, thanks for clarification. I'll get on top of riding it with those additives. Either way, thank you for mentioning the 4 turns, as it was only 1/4 out. So I'm happy I went poking around.
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Offline Laitch

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Re: '94 K75S Appropriate AFM screw position
« Reply #7 on: October 06, 2019, 06:27:03 PM »
The AFM screw I'm talking about is the screw under the little rubber cap on top of the air box. Forgive me if I misnamed it.
johnny, I know the AFM screw has been touched before because when i popped the rubber thing off, it had been misshaped like someone tried to jam it back in there.
You've misidentified it. How much hope is there for a remedy here if posting photos in correct orientation seems out of reach or unimportant?

Anyway, if under that cap on the air box—which can only be mounted correctly on the air box in a certain orientation—is a 5mm hex fitting, you've been adjusting carbon monoxide (CO) level. That CO test is done with an exhaust gas analyzer after a throttle body balance tune up and it's probably all whack now. It is not an air flow meter adjustment. You need a manual. The Clymer manual explains this.

One component that you haven't described in your work is the condition of the coolant temperature sensor. If that is malfunctioning, good performance will be problematic. What color are the spark plugs after the engine has been running.

The way to deal with a newly acquired K75 is to go over it like member mlytle did. Take a look here.

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https://tinyurl.com/RillRider

Offline johnny

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Re: '94 K75S Appropriate AFM screw position
« Reply #8 on: October 06, 2019, 06:28:35 PM »
greetings...

a few years agoi  had a chance to buy the 1st k1100rs in the usa... it was titled to bmw na... was used for tv commercials and magazine pieces and general propagnda...

they said factory service from day 1... butts had no records... it was in beverly hills... i gotts to ride  the santa monica mountains on it... it was a mess... i bet it was never serviced...

the reason im telling you this... before riding a thousand miles in 2 days... id take a look at the splines...  proally has 25 year old molly on thete if any at all..

j o
  • :johnny i parks my 96 eleven hundert rs motobrick in dodge county cheezconsin  :johnny

Offline 1ockdown

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Re: '94 K75S Appropriate AFM screw position
« Reply #9 on: October 06, 2019, 06:33:56 PM »
Johnny, I'm already working on getting that done. I saw your post about the Castrol( I think) grease and that's what I'll roll with. I'll go back to the post and confirm.

Laitch, when I uploaded the photos, they weren't in that orientation, ill figure out how to fix it. I followed the Rob Lentini "Lean Drop" method of adjusting the mixture on two valve K bikes.
  • My garage in New York
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Offline johnny

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Re: '94 K75S Appropriate AFM screw position
« Reply #10 on: October 06, 2019, 06:43:15 PM »
greetings...

once again... is it this screw...


* filterhus.JPG (45.18 kB . 747x562 - viewed 58 times)

you see... i poasted a photo of a screw when you should have poasted a photo of the screw...

if so it is all way in and 4 turns out for oe...

j o
  • :johnny i parks my 96 eleven hundert rs motobrick in dodge county cheezconsin  :johnny

Offline 1ockdown

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Re: '94 K75S Appropriate AFM screw position
« Reply #11 on: October 06, 2019, 06:43:52 PM »
yes Johnny, that screw.
  • My garage in New York
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Offline johnny

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Re: '94 K75S Appropriate AFM screw position
« Reply #12 on: October 06, 2019, 06:52:13 PM »
greetings...

its all the way in and 4 turns out for oe...

look... you need to be specific here at motobrick.com... poast photos screenshots... call it what it is by use of the fische and manual...

laitch is right... you are a mess... you are lucky brunhilda has not banned you yet...

j o
  • :johnny i parks my 96 eleven hundert rs motobrick in dodge county cheezconsin  :johnny

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