BMW K bikes (Bricks)

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clnl_hrkr

clnl_hrkr
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So the Bike and what works:



  1. BMW K100 RS 1985 (Modified as a Cafe racer by previous owner, so hacked to bits)
  2. Bike was running fine before Winter (UK)
  3. I had the tank off and changed spark plugs over winter, never tried to start it
  4. Connected it all back up and it won't start
  5. Checked side fuses, all okay
  6. Checked the new spark plugs, all sparking
  7. Checked the fuel pump and injectors all working fine, spraying okay when turns over.
  8. Engine cranks around on starter
  9. Battery is fine
  10. Top frame Earth is good (I cleaned it up again anyway)
  11. The bike is getting air(i hope , as how would it not?)


I've cranked i over for quite a few battery runs and it never FIRES it just cranks on and on. BUT when I removed all the injectors to see if they were spraying the bike DID fire up for a couple of seconds. What?????

What on earth am I missing here, it has spark, fuel and air, surely it should FIRE over now right?

Have I flooded it beyond good or what? 
Is it a sensor thing? 

Could some bright spark please help me?

Kind regards,
Jon

    

MartinW

MartinW
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Are the spark plugs wet or dry? If wet remove the Fuel Pump ( Kraffstoppe) fuse #6, and try to start it. It should run on the residual fuel in the combustion chamber. If it still floods after replacing the fuse check the temperature sensor connection and the sensor.
Regards Martin.


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K75s Hybrid
    

Born Again Eccentric

Born Again Eccentric
Life time member
Life time member
Check the fuel pump plug (at the rear of the fuel tank on the right hand side) - you wouldn’t be the first not to plug it back in after the tank has gone back on. If it is plugged in, various forum members have previously had issues with poor connection due to the sockets splaying out and not making a good electrical contact.

Trouble with cafe hacks is you can never be quite sure what things have been removed, so trouble shooting is that much harder. Always start with the obvious though.


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Help!! Bike won't start with Spark, Fuel and Air???!! Uk-log10 Help!! Bike won't start with Spark, Fuel and Air???!! Sco-lo15Help!! Bike won't start with Spark, Fuel and Air???!! Eu-log10
                              Paul  Help!! Bike won't start with Spark, Fuel and Air???!! 905546712

"Heidi" K100LT 1991 (Grey) (VIN 0190172 Engine No. 104EB 2590 2213) - 5th owner. January 2014 (34,000 - 61,000 miles and counting....)
"Gretel" K100LT 1989 (Silver Grey) (VIN 0177324 Engine No. 104EA 2789 2211) - 4th+ owner. September 2015 (58,500miles and counting....). Cat C Insurance write-off rebuild Feb 17
"Donor" K100LT 1990 (Red)  (VIN 0178091 Engine No. 4489 2024) - 6th & final owner (crash write-off now donor bike).   June 2012 (73,000 miles) to November 2013 (89,500 miles)
    

clnl_hrkr

clnl_hrkr
active member
active member
Thanks for your advice guys,

The plugs looked a bit wet but not dripping if that's a thing. The bike had pretty low compression before winter when I last did a test, so after whating a youtube video on K bikes the advice is to put 10cc's of motor oil in each cylinder to regain compression and get it starting again. As after a long sit over winter they can lose more compresion.

I'm really crap with electrical stuff but I have a mulimeter and love learning so I'll try your suggestions. 

I'll update tomorrow hopefully!

Thanks,
Jon

    

clnl_hrkr

clnl_hrkr
active member
active member
@MartinW wrote:Are the spark plugs wet or dry? If wet remove the Fuel Pump ( Kraffstoppe) fuse #6, and try to start it. It should run on the residual fuel in the combustion chamber. If it still floods after replacing the fuse check the temperature sensor connection and the sensor.
Regards Martin.

Hi Martin,

Would you be able to explain the relationship between the temp sensors and the bike starting? 

Thanks,
Jon

    

moriarti

moriarti
Silver member
Silver member
oil in the bores as per you tube video is the best guess Help!! Bike won't start with Spark, Fuel and Air???!! 112350


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1984 k100 rs red/black VIN  0004449
    

clnl_hrkr

clnl_hrkr
active member
active member
@moriarti wrote:oil in the bores as per you tube video is the best guess Help!! Bike won't start with Spark, Fuel and Air???!! 112350
Will report back sir.

Moriarti, if you're in Yorkshire do you ever get down Squires Cafe??

    

MartinW

MartinW
Life time member
Life time member
The temperature sensor sends information to the computer. If the sensor or it's connection is faulty the computer over enrichens the mixture causing flooding. If you can get it to run with the fuse out with a bit of throttle manipulation. Then as the engine dies you can if your quick enough jam the fuse back home, and keep it running by playing with the throttle. A faulty connection has caught me out twice in 20+ years and I've managed to limp home doing this. On the way home the connection came god and it ran normally. The sensor is positioned so it cops a fair bit of road spray (salt) and crap. I eventually chose to thoroughly clean the connection and waterproof it with thick silicone grease, it's been fine since.
Regards Martin.


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K75s Hybrid
    

moriarti

moriarti
Silver member
Silver member
Help!! Bike won't start with Spark, Fuel and Air???!! 214585
Im based in Brighouse and yes i get over to the cafe  lol!
i even take my own pork pies with me  Help!! Bike won't start with Spark, Fuel and Air???!! 214585


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1984 k100 rs red/black VIN  0004449
    

moriarti

moriarti
Silver member
Silver member
My 1984 doesn't have the 2 part temp sensor and i would think yours doesn't ether if so life has become so much simpler.Post your bike details to help members with their answers inc vin number study


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1984 k100 rs red/black VIN  0004449
    

11Back to top Go down   Help!! Bike won't start with Spark, Fuel and Air???!! Empty UPDATE on Sun Jan 12, 2020 12:24 pm

clnl_hrkr

clnl_hrkr
active member
active member
So I fully charged the battery and added a little engine oil inside each cylinder to make better compression, and no start still. I might do a compression test next.

As mentioned before, the only time it started (during this diagnosis project) is when I removed all 4 Injectors, any guesses as to why this might have worked? 

During last Summer it was running fine starting up on first hit of the button, I then did some clean up work over winter, removing the tank, changing the spark plugs and did some frame painting work. I havent done anything major or extreme.

Any suggestions on a logical step by step to diagnose further? 

One thought I have is the Injectrs were spraying but I'm not sure if it was powerful enough, so it may be the pump. But the pump does run when you press the start button. And there is defintely spark. Could Air be an issue, if so how?

Thanks guys

    

MartinW

MartinW
Life time member
Life time member
After failing to start are the spark plugs wet or dry??
Regards Martin.


__________________________________________________
K75s Hybrid
    

Laitch

Laitch
Life time member
Life time member
What is the battery's output when it's under load? The battery might be too weak to get it started.


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1995 K75 73,000 miles
Help!! Bike won't start with Spark, Fuel and Air???!! Usa-lo10
    

clnl_hrkr

clnl_hrkr
active member
active member
@MartinW wrote:After failing to start are the spark plugs wet or dry??
Regards Martin.
With my limited experience I'd say they are dry, they certainly didnt look like they were covered in fuel. I'm starting to think even though everything is working, there may not be enough power from the battery as suggested. I'll check the battery under load tomorrow.I also have another bike so I may swap batteries and see if that fixes.

    

clnl_hrkr

clnl_hrkr
active member
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@Laitch wrote:What is the battery's output when it's under load? The battery might be too weak to get it started.
Not sure, Im going to check the battery tomorrow with my multimeter and also swap it for another I have

    

jbt

jbt
Silver member
Silver member
@clnl_hrkr wrote:Thanks for your advice guys,

The plugs looked a bit wet but not dripping if that's a thing. The bike had pretty low compression before winter when I last did a test, so after whating a youtube video on K bikes the advice is to put 10cc's of motor oil in each cylinder to regain compression and get it starting again. As after a long sit over winter they can lose more compresion.
Don't trust what you can see on Youtube.
Winter does not lower compression.
Wear does.

Pouring oil the combustion chamber is a good thing only if you intend to measure compression, because it's supposed to temporary seal the piston/cylinder junction and allows to compare with a previous measure without oil to validate or not if the low compression is due to worn segments or leaking seat valves. Or valves under permanent constraint, but of course, you have previously checked this before, don't you?
Note: this method only apply to vertical cylinders as long as you're on the earth.
In other cases, if you live in interstellar location or if your motorcycle is a K bike with horizontal cylinders, the only consequence of pouring oil in the cylinder will be to kill your plugs -and eventually your engine as oil is uncompressible. Connecting rods are.

Buy new plugs, seriously clean your tank, buy new fuel, check that the 4 injectors are spitting the correct amount of oil during 1 minute (be careful, no erratic spark during this test...) use a big car battery shunt on your bike, a low amp. battery won't deliver enough to start your engine, particularly if the starter has to cope with 4 cylinders full of oil besides having to deal with demanding fuel pump and an ignition system which turns to be inoperant under 7-8 Volts.

    

92KK 84WW Olaf

92KK 84WW Olaf
Life time member
Life time member
You should be aware K engines last well and 100k miles should not see significant reduction in compression.

A few things in my mind......

Fuel lines at the front of the tank connected right way round?
Plug connector if it is in the front left of the tank is prone to poor connection but you can open the pins a little.
Frame painting means paint at the earth point under the tank may cause electrical isolation so check that earth point.
FICU unit under the seat and the ICU unit at the head stock have big plugs and pins need to be cleaned up from time to time as routine maintenance, higher risk if the are off the bike for a while as you can get surface build up.


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1992 K100LT 0193214 Bertha Alaska 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 100,380 miles
1983 K100RS 0011171 Fricka 606 29,495 miles Damn K Pox Its a Bat outta Hell No 33,600 miles
    

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