BMW K bikes (Bricks)


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1Back to top Go down   Really rough idle k100 Empty Really rough idle k100 Mon Sep 02, 2024 9:08 pm

amart0300

amart0300
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Hello I have a 1985 K100 that idles roughly. I have changed out the fuel pump and filter. I have replaced the top and bottom throttle body rubber bits and the vacuum caps. Injectors were also cleaned. New spark plugs as well. A new temperature sensor was also installed. The bike will only start with the choke on and if i hold down the green button it will idle quite smooth (at a fast rpm). Turning the choke off the bike quickly goes down in rpm and dies.

    

2Back to top Go down   Really rough idle k100 Empty Re: Really rough idle k100 Mon Sep 02, 2024 10:51 pm

amart0300

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Replaced the fuel pressure regulator just now still showing the same symptoms. Bike will only start with the choke on, and it will rev pretty high. Turning the choke off will cause the engine to fall 1000rpm and die. Bike has had the throttle body upper and lower rubber replaced. New fuel pump and filter. New spark plugs. New Coolant Temp sensor. Injectors have been cleaned professionally. New battery. Air box door swings open and closed freely. Bike will backfire and pop when it is on with the choke.

    

3Back to top Go down   Really rough idle k100 Empty Re: Really rough idle k100 Mon Sep 02, 2024 10:53 pm

amart0300

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4Back to top Go down   Really rough idle k100 Empty Re: Really rough idle k100 Mon Sep 02, 2024 11:18 pm

jbt

jbt
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What about valves clearance and throttle bodies synchronisation?


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Let us enjoy the transient delight
That fills our fairest day.
    

5Back to top Go down   Really rough idle k100 Empty Re: Really rough idle k100 Mon Sep 02, 2024 11:23 pm

amart0300

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i haven’t checked the valves most cause i’ve never done anything like that. and i would have to take the bike to go get the throttle bodies synced and i don’t know how to do that

    

6Back to top Go down   Really rough idle k100 Empty Re: Really rough idle k100 Tue Sep 03, 2024 12:21 am

Porto

Porto
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You must sycronise the throttle bodies. Don't just endlessly change parts. Just speeking from experience. They do go out. Sounds like you have a good machine otherwise

    

7Back to top Go down   Really rough idle k100 Empty Re: Really rough idle k100 Tue Sep 03, 2024 1:40 am

jbt

jbt
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amart0300 wrote:i haven’t checked the valves most cause i’ve never done anything like that. and i would have to take the bike to go get the throttle bodies synced and i don’t know how to do that
The very first thing to do is to find , read, and understand the workshop manual or Clymer's.
Valve clearance is a basic control anybody can do with a simple gauge.
Idem for the throttle bodies clearance, the only thing you need is a thin screwdriver and a light to check if the flaps are closed together. Too bad you did not check it when changing the rubbers.


__________________________________________________
Let us enjoy the transient delight
That fills our fairest day.
    

8Back to top Go down   Really rough idle k100 Empty Re: Really rough idle k100 Tue Sep 03, 2024 3:16 am

naut023

naut023
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Have you checked the coils and leads?


__________________________________________________
1985 K100RS
    

9Back to top Go down   Really rough idle k100 Empty Re: Really rough idle k100 Tue Sep 03, 2024 4:32 am

MartinW

MartinW
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Holding the green button down enrichens the mixture so you might be running lean and will have to adjust the mixture. This can be done using an exhaust gas analyser some motorcycle/ car shops might have one or if you can't access one you can use the lean drop method. Look up the lean drop method either on the forum or online. The adjustment screw requires the removal of a rubber plug on top of the RH front corner on top of the airbox. Once the rubber plug has been removed an (5mm?)Allen key can be inserted into the hole. Adjustments must be made in very small increments and after every adjustment the idle must be allowed to settle. Screwing the adjustment screw in richens the mixture screwing the screw out leans it out. If you join the local BMW motorcycle club they might have a exhaust gas analyser and someone to help.
Regards Martin.


__________________________________________________
1992 K75s
    

10Back to top Go down   Really rough idle k100 Empty Re: Really rough idle k100 Tue Sep 03, 2024 5:39 am

amart0300

amart0300
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naut023 wrote:Have you checked the coils and leads?
i haven’t

    

11Back to top Go down   Really rough idle k100 Empty Re: Really rough idle k100 Tue Sep 03, 2024 5:40 am

amart0300

amart0300
active member
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MartinW wrote:Holding the green button down enrichens the mixture so you might be running lean and will have to adjust the mixture. This can be done using an exhaust gas analyser some motorcycle/ car shops might have one or if you can't access one you can use the lean drop method. Look up the lean drop method either on the forum or online. The adjustment screw requires the removal of a rubber plug on top of the RH front corner on top of the airbox. Once the rubber plug has been removed an (5mm?)Allen key can be inserted into the hole. Adjustments must be made in very small increments and after every adjustment the idle must be allowed to settle. Screwing the adjustment screw in richens the mixture screwing the screw out leans it out. If you join the local BMW motorcycle club they might have a exhaust gas analyser and someone to
help.
Regards Martin.
I am in los angeles, i’ll try to look for a local bmw motorcycle club to help me out with adjusting the mixture

    

12Back to top Go down   Really rough idle k100 Empty Re: Really rough idle k100 Tue Sep 03, 2024 6:01 am

naut023

naut023
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amart0300 wrote:
naut023 wrote:Have you checked the coils and leads?
i haven’t
They are pretty easy to test with a multi-meter and if you already have a multi-meter it is free  Very Happy


__________________________________________________
1985 K100RS
    

13Back to top Go down   Really rough idle k100 Empty Re: Really rough idle k100 Tue Sep 03, 2024 1:54 pm

bad boy

bad boy
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jbt wrote:What about valves clearance and throttle bodies synchronisation?
@jbt
according to my trusted mechanic who has been servicing Ecos for decades, the valve clearance is hardly ever an issue with the venerable Flying Brick engine.
He told me that they used to check them it at Peraves CH but stopped doing so after finding again and again that the OEM valve clearances remain correct for many, many a year.
BMW have been building reliable engines for over a century.

And yes, throttle bodies sync is a different story.
amart0300, please go and check it.

@amart0300
if pressing the choke makes your bike run better, the mixture is too lean.
A very common cause is a leaky intake tract which adds more air to the previously correct mixture after the sensor has determined the right amount of gasoline injected.
Go and replace all the rubber stuff, as ageing makes it brittle and leaky.


__________________________________________________
Cheerz, David

Really rough idle k100 9438-010

____________________________________________________________________________
1997 Peraves Super Ecomobile: a Kevlar reinforced monocoque with outrigger wheels, seating two.
K75 fork, K100 monolever, headlight, indicators, K1100RS gearbox, K1200RS 589 instrument cluster, engine, rear wheel
    

14Back to top Go down   Really rough idle k100 Empty Re: Really rough idle k100 Tue Sep 03, 2024 3:56 pm

amart0300

amart0300
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bad boy wrote:
jbt wrote:What about valves clearance and throttle bodies synchronisation?
@jbt
according to my trusted mechanic who has been servicing Ecos for decades, the valve clearance is hardly ever an issue with the venerable Flying Brick engine.
He told me that they used to check them it at Peraves CH but stopped doing so after finding again and again that the OEM valve clearances remain correct for many, many a year.
BMW have been building reliable engines for over a century.

And yes, throttle bodies sync is a different story.
amart0300, please go and check it.

@amart0300
if pressing the choke makes your bike run better, the mixture is too lean.
A very common cause is a leaky intake tract which adds more air to the previously correct mixture after the sensor has determined the right amount of gasoline injected.
Go and replace all the rubber stuff, as ageing makes it brittle and leaky.
I replaced the upper and lower rubber on the throttle bodies and the vacuum line that runs to the FPR. Z pipe is in good condition still.

    

15Back to top Go down   Really rough idle k100 Empty Re: Really rough idle k100 Tue Sep 03, 2024 9:44 pm

Dai

Dai
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Life time member
What about the small vacuum caps on tb1 -> 3 and the vacuum tube on tb4? They all split, but the small rubber caps are more prone to it thatn the vaccum tube. Also check that the tube from tb4 to the fuel pressure regulator isn't crimped if the protective spring is missing (it often is).


__________________________________________________
1983 K100 naked upgraded to K100LT spec after spending time as an RS and an RT
1987 K100RT
Others...
1978 Moto Guzzi 850-T3, 1979 Moto Guzzi 850-T3 California,1993 Moto Guzzi 1100ie California
2020 Royal Enfield Bullet 500
    

16Back to top Go down   Really rough idle k100 Empty Re: Really rough idle k100 Tue Sep 03, 2024 10:46 pm

Two Wheels Better

Two Wheels Better
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Moved post from general Technical, Repair & Troubleshooting, to Technical, Repair & Troubleshooting - Engine & Transmission.


__________________________________________________
"A long ride is the answer to a question you will soon forget!" ~ Anonymous
1977 R75/7-100, '93 K11/K12 Big Block, '93 K1100RS, '95 R100 Mystic, '96 K1100RS, 2 x '98 K1200RS, '06 K1200R & '09 K1300GT
    

17Back to top Go down   Really rough idle k100 Empty Re: Really rough idle k100 Tue Sep 03, 2024 11:11 pm

amart0300

amart0300
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Dai wrote:What about the small vacuum caps on tb1 -> 3 and the vacuum tube on tb4? They all split, but the small rubber caps are more prone to it thatn the vaccum tube. Also check that the tube from tb4 to the fuel pressure regulator isn't crimped if the protective spring is missing (it often is).
Replaced with new vacuum caps and a new vacuum tube.

    

18Back to top Go down   Really rough idle k100 Empty Re: Really rough idle k100 Wed Sep 04, 2024 1:30 am

92KK 84WW Olaf

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Dai wrote:What about the small vacuum caps on tb1 -> 3 and the vacuum tube on tb4? They all split, but the small rubber caps are more prone to it thatn the vaccum tube. Also check that the tube from tb4 to the fuel pressure regulator isn't crimped if the protective spring is missing (it often is).

If yours is 1985 it also has a vacuum sensor...there is another vacuum pipe take off beside the fuel pipe at the front of the injector rail. This pipe is likely cracked and leaking. Just take it off and replace it with a vacuum cap.

You say the Z pipe is good BUT they can look good and be cracked too. I am in Ks long enough to find they only last about 5 years. I had to replace vacuum caps on my Sprint after only 12 months.

I have never had to adjust valve clearances.


__________________________________________________
1992 K100LT 0193214 Bertha Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red 578 bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 689 58,645 now 106,950 miles Deceased.
1983 K100RS 0011157 Fricka 606 Alaska Blue 29,495 miles Damn K Pox Its a Bat outta Hell Now 58,200 miles. 
1996 K1100LT 0233004 Lohengrin Mystic Red 38,000 miles currently 51,800 miles.
1983 K100RS 0004449 Odette R100 colours 58,000 miles. Sprint fairing now 63,390 miles

Past:
1968 Yamaha 80 YG1
1971 Yamaha 125 YAS-1
1968 Honda 125 SS
1970 Honda CD 175
1973 Honda CB500-4
Honda CX 500
    

19Back to top Go down   Really rough idle k100 Empty Re: Really rough idle k100 Wed Sep 04, 2024 1:33 am

amart0300

amart0300
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92KK 84WW Olaf wrote:
Dai wrote:What about the small vacuum caps on tb1 -> 3 and the vacuum tube on tb4? They all split, but the small rubber caps are more prone to it thatn the vaccum tube. Also check that the tube from tb4 to the fuel pressure regulator isn't crimped if the protective spring is missing (it often is).

If yours is 1985 it also has a vacuum sensor...there is another vacuum pipe take off beside the fuel pipe at the front of the injector rail. This pipe is likely cracked and leaking. Just take it off and replace it with a vacuum cap.

You say the Z pipe is good BUT they can look good and be cracked too. I am in Ks long enough to find they only last about 5 years. I had to replace vacuum caps on my Sprint after only 12 months.

I have never had to adjust valve clearances.
I removed the vacuum tube a replaced the port on the TB with a cap, the sensor is still back there with the leads disconnected and heat shrinked. Should I reconnect the leads to it?

    

20Back to top Go down   Really rough idle k100 Empty Re: Really rough idle k100 Wed Sep 04, 2024 1:36 am

amart0300

amart0300
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while leaving the vacuum line off and TB capped of course

    

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