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robmack

robmack
Life time member
Life time member
Helping a friend with his non-running 87 K75.  I've checked and double checked for all the elements needed to start - air, petrol, spark - but no go.  Usually I'm offering the advice but now I need some.

- brand new battery fully charged 13.17V resting voltage
- starter cranks healthily and engine turns over briskly
- brand new NGK DR7EA plugs, gapped properly.  I confirmed a healthy spark on all plugs
- fuel pump operating with the start switch and 1.5 seconds after release
- air filter clean
- injectors operating as I have used the screwdriver-as-a stethoscope trick to listen for clicks.  Clicks are  present on all three injectors.  
- At times after a cranking session, fuel leaks out of the exhaust between the header and muffler indicating fuel in getting into and out of the cylinders
- all plugs are wet with fuel
- tried the trick to unplug the tank connector and crank the starter.  Engine turns over but still does not catch.

What I have not yet done:
- I have not yet gone through each and every connector on the harness with Deoxit but that is my next step.

Interesting Observation:
I had to do some electrical work on the bike because connectors were mashed and McGivered by the previous owner.  Used parts from a doner bike to correct the mess.  During this electrical work, I cranked over the engine once and it caught, and ran for about 15 - 20 seconds.  No fuel tank at the time so this engine operation was with fuel left over in the cylinders and fuel hoses.

I'm hoping someone will point out the obvious (or not so obvious) that I have missed.  Why won't this engine catch and run?


__________________________________________________
Robert
1987 K75 @k75retro.blogspot.ca
http://k75retro.blogspot.ca/
    

moriarti

moriarti
Life time member
Life time member
Hi Robmack, Maybe its low compression due to fuel washing the bores,So try the old trick of putting oil in the bores via Plugholes, SOMETIMES simple works  Very Happy


Saw this done on K1100 by  Chris Harris on video worked a treat common problem according Need help with 87 K75 - all elements for engine start present but won't start.   What am I missing? 112350  to him. like you everything in line just wont run


__________________________________________________
1984 k100 rs red/black VIN  0004449
    

Point-Seven-five

Point-Seven-five
Life time member
Life time member
Rob, how long did you crank the engine with the tank disconnected?  It can sometimes take 15-20 seconds or more if there is a lot of fuel in the cylinders. 

Has the bike ever ran since your friend got it?  The rings may be stuck and there isn't enough compression.  A shot of oil in each cylinder might help get things going. 

Can you get it to fire on starting fluid?  Pull the plugs, dry them off and crank the engine a bit with them out.  Then put them back in and with the tank disconnected put a shot of starter fluid in the air box and give it a whirl.


__________________________________________________
Present:
1994 K75RT
1991 K100RS


Past:
1988 K100RS SE
1994 BMW K75S
1992 BMW K100RS
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

Point-Seven-five

Point-Seven-five
Life time member
Life time member
Also, if the above doesn't work, check the compression and/or the valve clearances.  A stuck or out of adjustment valve can prevent getting good compression, but that's a long shot in the dark. 

Another even longer shot would be an ignition timing issue.  You pulled the plugs and put them back so there is no chance that #2 and #3 were crossed by a previous owner. 

Last, and way, way out there is a possible Jetronic control problem.  Beyond that, the only other thing I can think of is really bad Karma.  I know you checked the tank and the fuel system is clean with good filters and injector screens.


__________________________________________________
Present:
1994 K75RT
1991 K100RS


Past:
1988 K100RS SE
1994 BMW K75S
1992 BMW K100RS
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

robmack

robmack
Life time member
Life time member
Cheers guys.  And thanks a bunch Point-Seven-Five.   I went for a long walk with the dog and when I returned, I cranked with a disconnected tank for 25 - 40 seconds.  Voila.  The engine fired up.   It seems I might have flooded the be-jesus out of the engine as I was testing all my electrical changes.

Now there is still fuel leaking out of the header-muffler connection even with the tank and pump disconnected.  So I am going to swap injectors with the donor bike and see if things improve.  It could be that the current injectors (1 or more) are not fully closing and allowing fuel to leak.

The bike was a runner but 3 yearsago, he's stored it in a garage without winterising it and there is has sat. So, it was butt ugly when he dropped the pair of bikes off at my place.  The bike is now running smoothly even with the pump disconnected.  I think there is great hope for the motorcycle; I just need to give it a bit more TLC and she'll respond.


__________________________________________________
Robert
1987 K75 @k75retro.blogspot.ca
http://k75retro.blogspot.ca/
    

Point-Seven-five

Point-Seven-five
Life time member
Life time member
Nice work, Rob!  You could try changing the injectors, but since you have it running, I would put some fresh fuel in the tank if you haven't done that already and add a good dose of Techron or Seafoam. 

Then run the engine until it warms up.  Do that a couple times the first day to mix the additive into the fuel and get it into the injectors.  Then run the engine a couple times every day for a few minutes.  After a week or so that should flush out any of the varnish that might be in the injectors and making them sticky.  Once it's running you can take it out for a short ride and give it some rpm's, that will tell you if you need to swap the injectors.


__________________________________________________
Present:
1994 K75RT
1991 K100RS


Past:
1988 K100RS SE
1994 BMW K75S
1992 BMW K100RS
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

robmack

robmack
Life time member
Life time member
Well bollocks!  The bloody bike is still refusing to start this morning after an evening of drying out. Still going to :
- replace the injectors
- clean all contacts with deoxit
- test compression and try the oil trick
- check valve gaps

I’ll keep posting here. Wish me luck.



Last edited by robmack on Mon Aug 01, 2022 8:34 pm; edited 1 time in total

http://k75retro.blogspot.ca/
    

Laitch

Laitch
Life time member
Life time member
¡Buena suerte, robmack!  Need help with 87 K75 - all elements for engine start present but won't start.   What am I missing? 1f389


__________________________________________________
1995 K75 81,000 miles
Need help with 87 K75 - all elements for engine start present but won't start.   What am I missing? Usa-lo10
    

Laitch

Laitch
Life time member
Life time member
I read no mention of the usual suspects in the lineup, robmack, namely the coolant temperature sensor function and the air flow meter vane.


__________________________________________________
1995 K75 81,000 miles
Need help with 87 K75 - all elements for engine start present but won't start.   What am I missing? Usa-lo10
    

robmack

robmack
Life time member
Life time member
Cheers @laitch. I’ll quickly check those as well while I’m in there with the deoxit.

@point-seven-five:  Failed to answer your question earlier about fuel. The fuel is fresh.  I threw out the old and replaced it with freshly pumped 91 Octane.  Also changed the fuel filter to a Napa 3032 Gold so those issues are dealt with. Also did a thorough visual check of the tank with it empty for grungy rubber bits; none visible.  Pump is pristine as well.

http://k75retro.blogspot.ca/
    

11Back to top Go down   Need help with 87 K75 - all elements for engine start present but won't start.   What am I missing? Empty K75 Starting problems Tue Aug 09, 2022 1:31 pm

Kr4mo

Kr4mo
active member
active member
robmack wrote:Helping a friend with his non-running 87 K75.  I've checked and double checked for all the elements needed to start - air, petrol, spark - but no go.  Usually I'm offering the advice but now I need some.

- brand new battery fully charged 13.17V resting voltage
- starter cranks healthily and engine turns over briskly
- brand new NGK DR7EA plugs, gapped properly.  I confirmed a healthy spark on all plugs
- fuel pump operating with the start switch and 1.5 seconds after release
- air filter clean
- injectors operating as I have used the screwdriver-as-a stethoscope trick to listen for clicks.  Clicks are  present on all three injectors.  
- At times after a cranking session, fuel leaks out of the exhaust between the header and muffler indicating fuel in getting into and out of the cylinders
- all plugs are wet with fuel
- tried the trick to unplug the tank connector and crank the starter.  Engine turns over but still does not catch.


I have had some experience with hard starting K75s.  They tend to flood way too easily.  I'd bet your injectors aren't closing properly and allowing fuel to seep in when sitting since the system is still under pressure.  Have a go with the other injectors.  Then send your injectors to Injector Experts in Rising Sun, Ohio.  $20 each plus shipping.  They have done several sets for me with great results.

What I have not yet done:
- I have not yet gone through each and every connector on the harness with Deoxit but that is my next step.

Interesting Observation:
I had to do some electrical work on the bike because connectors were mashed and McGivered by the previous owner.  Used parts from a doner bike to correct the mess.  During this electrical work, I cranked over the engine once and it caught, and ran for about 15 - 20 seconds.  No fuel tank at the time so this engine operation was with fuel left over in the cylinders and fuel hoses.

I'm hoping someone will point out the obvious (or not so obvious) that I have missed.  Why won't this engine catch and run?

    

92KK 84WW Olaf

avatar
Life time member
Life time member
robmack wrote:Helping a friend with his non-running 87 K75.  I've checked and double checked for all the elements needed to start - air, petrol, spark - but no go.  Usually I'm offering the advice but now I need some.

- brand new battery fully charged 13.17V resting voltage
- starter cranks healthily and engine turns over briskly
- brand new NGK DR7EA plugs, gapped properly.  I confirmed a healthy spark on all plugs
- fuel pump operating with the start switch and 1.5 seconds after release
- air filter clean
- injectors operating as I have used the screwdriver-as-a stethoscope trick to listen for clicks.  Clicks are  present on all three injectors.  
- At times after a cranking session, fuel leaks out of the exhaust between the header and muffler indicating fuel in getting into and out of the cylinders
- all plugs are wet with fuel
- tried the trick to unplug the tank connector and crank the starter.  Engine turns over but still does not catch.

What I have not yet done:
- I have not yet gone through each and every connector on the harness with Deoxit but that is my next step.

Interesting Observation:
I had to do some electrical work on the bike because connectors were mashed and McGivered by the previous owner.  Used parts from a doner bike to correct the mess.  During this electrical work, I cranked over the engine once and it caught, and ran for about 15 - 20 seconds.  No fuel tank at the time so this engine operation was with fuel left over in the cylinders and fuel hoses.

I'm hoping someone will point out the obvious (or not so obvious) that I have missed.  Why won't this engine catch and run?
Wrong spark plugs, NGK DR7EA plugs wont work.

You need D7EA, no R and make sure they have the bobbins on. D8EA will work fine if you cant get D7EA but do NOT use a plug with R.


__________________________________________________
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 0011171 Fricka 606 Alaska Blue 29,495 miles Damn K Pox Its a Bat outta Hell Now 40,490 miles. 
1996 K1100LT 0233004 Lohengrin Mystic Red 38,000 miles currently 42,640 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
    

Point-Seven-five

Point-Seven-five
Life time member
Life time member
Sharp eye, Olaf!!!  I blew right past the plug numbers.


__________________________________________________
Present:
1994 K75RT
1991 K100RS


Past:
1988 K100RS SE
1994 BMW K75S
1992 BMW K100RS
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

Porto

Porto
Silver member
Silver member
I’m with Robmack. However through my own error I rode with the r plugs in and original leads for two years no trouble. Now I’ve got NGK resistive leads and non resistive plugs, perfect. Also lifted the heat range by one on the NGK plugs. I would give it an Italian tune up when it starts running. From experience it is impossible to flood a k to point that you have fuel running out the header unless the injectors are stuck. Since it sar so long it was likely one or more where stuck. There a great bike, I wish I had a 75 as well my 100. Cheers

https://gpleather.com
    

robmack

robmack
Life time member
Life time member
This machine is getting the better of me.  Here's the latest:
- 3 freshly cleaned and flow tested injectors installed
- checked fuel pressure when cranking and running.  It was good at 37 PSI
- did the oil trick by adding oil into the cylinders to increase compression
- cleaned  connectors with deoxit

I have not yet:
- checked valve clearances
- checked compression because my compression tester is the wrong thread size and pitch
- swapped ICU or ECU with known good working units

I can run the engine with the tank disconnected and it will run for a good 30 seconds (very smooth and strong sounding) until all fuel is exhausted.

I tried the following.  I got the engine running without the tank then, while running, plugged in the tank.  Within a couple of seconds, the engine began to sputter, then died shortly after that.

I've got D7EA plugs on order (still using the DR7EAs for the moment).  I am assuming that the engine is flooding when I plug in the tank so I just don't know what is causing the it.


__________________________________________________
Robert
1987 K75 @k75retro.blogspot.ca
http://k75retro.blogspot.ca/
    

MartinW

MartinW
Life time member
Life time member
Rob check the temperature sensor and it's connections.
Regards Martin.


__________________________________________________
K75s Hybrid
    

kennybob

kennybob
Silver member
Silver member
robmack wrote:...
I can run the engine with the tank disconnected and it will run for a good 30 seconds (very smooth and strong sounding) until all fuel is exhausted.

I tried the following.  I got the engine running without the tank then, while running, plugged in the tank.  Within a couple of seconds, the engine began to sputter, then died shortly after that.
Here are some questions/suggestions on this.

How are you supplying fuel when "running" without the fuel tank?

Have you checked for a plugged return line from the fuel rail? 
Blocked or defective fuel pressure regulator, cracked vacuum line to regulator?  
Crossed the connections for the fuel supply and return lines from the tank to the fuel rail and regulator?

    

robmack

robmack
Life time member
Life time member
Hi @kennybob.  Fuel being supplied to the engine is what remains in the fuel lines after I crank over the engine and then disconnect the fuel pump.  It's gravity fed into the injectors until it is exhausted.

There is no blockage in the fuel supply.  I am getting full recommended pressure while the fuel pump is operating measured at the outlet of the fuel rail, and I am seeing a healthy return flow back into the tank.  I also confirm that the connections to the tank are not crossed.

I'm suspicious of the temperature sender in the stand pipe that supplies temp information to the ECU.  Following @Martin's advice, I measured the resistance and it is higher than I believe it should be for the given ambient temperature at the time.  That means the sender is telling the ECU that the outside temperature is cold and it should increase fuelling; exactly the problem I'm experiencing.  I have yet to get around to cleaning the contact but I'll be replacing the temperature sender with the one from the donor bike after I've tested it on the bench.  Means emptying the cooling system on two bikes ... Yuch.

Thanks for your help.


__________________________________________________
Robert
1987 K75 @k75retro.blogspot.ca
http://k75retro.blogspot.ca/
    

92KK 84WW Olaf

avatar
Life time member
Life time member
Make sure the temperature sender is off a 2v K.

4v ones look identical but are not.

Dont use ptfe or anything like that.


__________________________________________________
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 0011171 Fricka 606 Alaska Blue 29,495 miles Damn K Pox Its a Bat outta Hell Now 40,490 miles. 
1996 K1100LT 0233004 Lohengrin Mystic Red 38,000 miles currently 42,640 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
    

robmack

robmack
Life time member
Life time member
Thanks Olaf.  I'm aware of those aspects. Both bikes (donor and the patient) are 87's.


__________________________________________________
Robert
1987 K75 @k75retro.blogspot.ca
http://k75retro.blogspot.ca/
    

Arlina

Arlina
Moderator
Moderator
Sounds very familiar.....

Got my headlight on the tempsensor.
Measure pin 10 on the EFI connector to ground, at 20 C it should be 2500 Ohm.
Possible corrosion between the sensor and housing, also did you check the earthlines under the tank?

Need help with 87 K75 - all elements for engine start present but won't start.   What am I missing? Water%20temperature


__________________________________________________
Need help with 87 K75 - all elements for engine start present but won't start.   What am I missing? Eu-log10  K1100RS/LT - R1200RT - R1100RS (RIP) - Cagiva SST 350 Ala Verde - K75LT project - K75 Schurgers - K75S
    

robmack

robmack
Life time member
Life time member
@Arlina, I just went out into the garage and retested the temperature sensors on both bikes; the patient bike reads 1910 Ohms and the donor bike reads 1896 Ohms.  Ambient temperature is 26°C but maybe a tad warmer in the garage (30°C).  According to Bert's troubleshooting guide, these values are almost right on point (1800 Ohms @30°).  So back to head scratching.  It doesn't look to be temperature sensor related. Sad


__________________________________________________
Robert
1987 K75 @k75retro.blogspot.ca
http://k75retro.blogspot.ca/
    

MartinW

MartinW
Life time member
Life time member
Rob a faulty sensor connection can be intermittent. Mine had such a problem and jamming my hand in and manipulating the plug would give a temporary fix. A permanent fix required removing and cleaning the threads and cleaning and tightening the connector.
Regards Martin.


__________________________________________________
K75s Hybrid
    

Arlina

Arlina
Moderator
Moderator
Did you swap the EFI with another bike?


__________________________________________________
Need help with 87 K75 - all elements for engine start present but won't start.   What am I missing? Eu-log10  K1100RS/LT - R1200RT - R1100RS (RIP) - Cagiva SST 350 Ala Verde - K75LT project - K75 Schurgers - K75S
    

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