BMW K bikes (Bricks)

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1Back to top Go down    Idle & Sounds on Thu May 24, 2018 7:25 am

George_Pap

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Hi all.
After the recent problem i had with the clogged fuel tank vent pipe bike now is back on the road. Put about 150km on it and in general it seems ok.
The only problem i face, since i m totally noob in K bikes is its idle behaviour.
Bike needs more than 5 minutes with the choke on and on the very start actually needs the second scale of the choke lever. For 3-4 minutes. After that period engine needs another 4-5 minutes on the first choke scale and stabilises its rpm to 1000-1100 a noise is heard from the engine - crankcase (?)
Since a video will give you the picture i would like your experience on this.

Thank you.




Last edited by George_Pap on Thu May 24, 2018 7:36 am; edited 1 time in total


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K100RT (Early 1985 -nonABS)
    

2Back to top Go down    Re: Idle & Sounds on Thu May 24, 2018 7:28 am

George_Pap

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at 00:41 you can hear exactly the sound that worries me. It goes away after 10 minutes warm up.
After that 10 minutes of the engine working idle sets to steady 1100 rpm and that noise is barely audible.


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3Back to top Go down    Re: Idle & Sounds on Thu May 24, 2018 7:46 am

Dai

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Diesel knock! Very Happy I think we've all had that at some point - search the forum for lots of possible answers. The most likely causes are:

1. Dirty injectors
2. Air leak on the inlet stubs
3. Unbalanced throttle bodies.

If the RPM stabilises at 1100, I'd be inclined towards the air leak theory initially because idle RPM is 960-980 according to BMW. It's not something that will do any damage as it's (only) a misfire.


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'83 K100 upgraded to K100RS spec
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'78 Moto Guzzi 850-T3, '79 Moto Guzzi 850-T3 California,'93 Moto Guzzi 1100ie California,
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4Back to top Go down    Re: Idle & Sounds on Thu May 24, 2018 7:56 am

George_Pap

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@Dai wrote:Diesel knock! Very Happy I think we've all had that at some point - search the forum for lots of possible answers. The most likely causes are:

1. Dirty injectors
2. Air leak on the inlet stubs
3. Unbalanced throttle bodies.

If the RPM stabilises at 1100, I'd be inclined towards the air leak theory initially because idle RPM is 960-980 according to BMW. It's not something that will do any damage as it's (only) a misfire.
Hey Dai!

I've read almost everything SmileBut reading finally made me terrify! Monkey nuts, Crankshaft pivots, Cam chain, Tensioners, even thermostat problems.
God, i m more confused than ever !
Thats why i've posted the sound, hopping somebody to respond " Yes!!! Its the X thing, had the same sound! "

Which places are prone to air leak so to search?By inlet stubs, you mean the four rubber hoses that go into the throttle bodies? Have in mind that this sound became worse after patching the leaking crankcase breather hose !


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5Back to top Go down    Re: Idle & Sounds on Thu May 24, 2018 9:04 am

Dai

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The four inlet stubs under the throttle bodies that bolt to the crankcase. Spray some WD40 (or similar) around them when the engine is running. If the RPM suddenly goes up and the knocking stops, you've found the air leak.


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'83 K100 upgraded to K100RS spec
Others...
'78 Moto Guzzi 850-T3, '79 Moto Guzzi 850-T3 California,'93 Moto Guzzi 1100ie California,
'03 Suzuki Blandit GSF600SK3 (NFS any more because wifey has claimed it)
    

6Back to top Go down    Re: Idle & Sounds on Thu May 24, 2018 10:28 am

duck

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FYI: WD-40 is no longer as flammable as it used to be. It still says flammable on the can but apparently the safety Nazis got to them so it is no longer as fun as it used to be. (Made great blow torches with dad's when I was a kid.)


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Current stable:
86 Custom K100 (standard fairing, K75 Belly pan, Ceramic chromed engine covers, paralever)
K75 Frankenbrick (Paralever, K11 front end, hybrid ABS, K1100RS fairing, radial tires)
86 K75C Turbo w/ paralever
94 K1100RS
93 K1100LT (x2)
91 K1
93 K75S (K11 front end)
91 K75S (K1 front end)
14 Yamaha WR250R
http://www.ClassicKBikes.com
    

7Back to top Go down    Re: Idle & Sounds on Thu May 24, 2018 10:33 am

George_Pap

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@Dai wrote:The four inlet stubs under the throttle bodies that bolt to the crankcase. Spray some WD40 (or similar) around them when the engine is running. If the RPM suddenly goes up and the knocking stops, you've found the air leak.

will blow some butane gas with my flame torch ( Dremmel ). Guess will do. Smile


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8Back to top Go down    Re: Idle & Sounds on Thu May 24, 2018 10:33 am

George_Pap

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@duck wrote:FYI: WD-40 is no longer as flammable as it used to be. It still says flammable on the can but apparently the safety Nazis got to them so it is no longer as fun as it used to be. (Made great blow torches with dad's when I was a kid.)

thank you! i second that!


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9Back to top Go down    Re: Idle & Sounds on Thu May 24, 2018 11:33 am

Two Wheels Better

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What's the condition of the S-shaped hose which you can see near the throttle position sensor, which goes from engine to bottom corner of the airbox? In the brief flash of it in your video it looked like it had been taped up. Any cracks causing leaks will make the idle sound like a box of rocks. One quick way to eliminate the engine breather or vent hose as a source of poor idle/performance is to unscrew the engine oil filler cap on the right hand side whilst idling and note the significant idle drop. If the idle does drop further the hose is likely not a cause.

I use a propane torch with a very, very small stream of gas (not lit, of course), to determine air leaks at the throttle body rubber mounts.


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1987 K100RS, '93 K11/K12 hybrid 'Big Block', '09 K1300GT, '07 K1200R, '04 R1150RT, '95 R100 Mystic, '77 R75/7.
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10Back to top Go down    Re: Idle & Sounds on Thu May 24, 2018 11:57 am

George_Pap

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@Two Wheels Better wrote:If the idle does drop further the hose is likely not a cause.

Thank you. I have already checked that S hose. It's the crankcase breather hose as described in clymers . Found out It was cracked at the end that goes into the air box and as you correctly noticed I patched it with a fair amount of soft electrical tape till I receive the original .
Do you think that it might still be leaking? I mean is the pressure too high there?


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11Back to top Go down    Re: Idle & Sounds on Thu May 24, 2018 12:02 pm

Two Wheels Better

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@George_Pap wrote:
@Two Wheels Better wrote:If the idle does drop further the hose is likely not a cause.

Thank you. I have already checked that S hose. It's the crankcase breather hose as described in clymers . Found out It was cracked at the end that goes into the air box and as you correctly noticed I patched it with a fair amount of soft electrical tape till I receive the original .
Do you think that it might still be leaking? I mean is the pressure too high there?
It's a chance. Pop off the oil filler cap and you'll know.


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1987 K100RS, '93 K11/K12 hybrid 'Big Block', '09 K1300GT, '07 K1200R, '04 R1150RT, '95 R100 Mystic, '77 R75/7.
Have we accomplished half of what we dreamt we would? There may still be time.
    

12Back to top Go down    Re: Idle & Sounds on Thu May 24, 2018 12:07 pm

George_Pap

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Read that in a post and did that test already .Engine stalls and almost goes out.


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