Author Topic: 1987 K75S no start, has spark & fuel  (Read 15404 times)

Offline elementarydeardata

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1987 K75S no start, has spark & fuel
« on: December 30, 2015, 06:55:07 PM »
Back in October, I bought an '87 K75S as a winter project (who knew it wasn't going to get cold in New England for two more months). I've wrenched on a lot of old Hondas and cars, but this is my first BMW and my first fuel injected bike. When I bought the bike, it needed all of the parts inside the fuel tank (fuel pump, filter, hoses and sending unit) replaced and a new master cylinder for the front brake. I also replaced the battery because it wasn't cranking well. (the bike was so cheap that I didn't mind all of this), and had Mr. Injector clean my injectors.

After replacing these parts (minus the master cylinder, still working on that), this is what I've ended up with: The bike cranks, has spark, and is spraying fuel in all 3 cylinders. I've been going through that PDF document by the K100 Forum user "Crazy Frog" that I've found floating around on several forums and testing the various parts. So far, I'm getting:

Spark and fuel in all 3 cylinders, I hear the fuel pump running, I've tested the fuel pressure and am getting 36psi. I hear some thumping noises coming from the throttle bodies/plenum area, and a little smoke comes out of the exhaust. I took the air filter housing off and i can see the air vane on the airflow meter moving.

I've been through his flowchart, still no joy. I can hear it fire occasionally as I crank it over, but nothing that sticks. Here is a video I took of the issue before I had to give it a rest when things got crazy at work:

Let me know if you see anything I'm missing, I seem to be pretty stuck. Thanks!

  • Hartford, CT
  • 1987 K75S
1987 BMW K75S

Offline Laitch

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Re: 1987 K75S no start, has spark & fuel
« Reply #1 on: December 30, 2015, 07:11:28 PM »
Welome. Be sure to visit the "No Start" section of the Workshop and try everything there twice. Your bike sounds like a Cuban drumming circle.  I don't recommend running the starter for more than 5 seconds. New battery or not, you may weld your starter relay contacts.

At which block are you stalled in Crazy Frog's chart?

Be sure you've explained everything you've done already so you don't deprive us of valuable Hulu and Netflix time while we instruct you to do something you've already done.
  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles

Offline johnny

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Re: 1987 K75S no start, has spark & fuel
« Reply #2 on: December 30, 2015, 08:08:59 PM »
greetings...

you gotts it on a battery tender donts you...

before i tell you your plug wires are crossed... you must first do 3 things...

#1...

#2...

#3...

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

Offline elementarydeardata

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Re: 1987 K75S no start, has spark & fuel
« Reply #3 on: December 30, 2015, 08:34:57 PM »
Hahah much respect to the Netflix time!

Here's what I've already done on crazy frog's flowchart: Since the starter was cranking, I skipped to the second page and tested the injection system. I had pressure at the fuel rail (36psi), so I pulled the rail and made sure all injectors were squirting. Everything looked good. Next, I went through with testing the EFI with a multi meter. The only one of the tests I was sketchy on was the water temp sensor, because it was damn cold when I did it (42 F). I also tested the mass air flow sensor and the hall effect sensor with a 12v LED. Everything checked out.

The funky bongo drum noises are coming from the intake manifold/throttle body area. Is there anything I should look for here?

I'll try the roll backwards starter cleaning thing tomorrow morning, the starter sounds fine, but I'm new to these bikes, I'll give it a shot.
  • Hartford, CT
  • 1987 K75S
1987 BMW K75S

Offline Laitch

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Re: 1987 K75S no start, has spark & fuel
« Reply #4 on: December 30, 2015, 08:42:56 PM »
Start here and read through the responses, elem.
http://www.motobrick.com/index.php/topic,3942.msg24469.html#msg24469
  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles

Offline elementarydeardata

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Re: 1987 K75S no start, has spark & fuel
« Reply #5 on: December 30, 2015, 10:45:57 PM »
Thanks for pointing me towards that post. I was getting like 10k ohms across pins 10 and 13, but it was chilly in the garage so I drained the coolant, pulled the sensor and took it inside. It's 69 degrees F, or 20.5 C in my kitchen right now and the sensor is reading 4.62k ohms. Crazy frog's guide says I should be getting 2.5k ohms at this temperature.

The post Laitch linked to suggested that a high reading could cause flooding. Does anyone know if my reading is high enough to cause this?
  • Hartford, CT
  • 1987 K75S
1987 BMW K75S

Offline Martin

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Re: 1987 K75S no start, has spark & fuel
« Reply #6 on: December 31, 2015, 01:49:19 AM »
Ele to see if it's flooding pull the spark plugs and have a look if they're wet.  If they're wet dry out plugs as much as you can. Pull the fuel pump fuse No 6 earth all plugs & crank over to clear excess fuel. replace plugs &  leads ( You don't have to dry it out completely the  next stage will do that ), with fuel pump fuse still out crank engine, it should start with the residual fuel still in combustion chamber. Once it has started it will start to die, as it dies push in the fuel pump fuse you should be able to get it to run, you will have to manipulate the throttle. It helps to have an assistant to work the throttle while the fuse is replaced, if this works what you have got is either a bad temperature sensor or a bad connection.
Regards Martin
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Offline The Mighty Gryphon

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Re: 1987 K75S no start, has spark & fuel
« Reply #7 on: December 31, 2015, 10:36:25 AM »
It sounds to me like your firing order is wrong.   

Double and triple check the plug wires that you have them on the correct plugs.  If I am not mistaken, the one for cylinder #3 is longer than the one for #2 and it is easy to get them mixed up. 

Also check to make sure your plugs have the "nut" that goes on the terminal, and that the plug cap is firmly pushed down on the plug.
  • In my garage in Marilla, NY
  • '91K100RS White/Blue
Current:
'91 K100RS16V "Moby Brick Too"

Past:
'94 K75RT "Ilsa, She Wolf of the SS"
'92 K100RS16V "Moby Brick" (RIP, deceased in a vehicular assault)
'94 K75S Special Edition Dakar Yellow "Cheetos"
'89 K100RS Special Edition "Special Ed"

Offline elementarydeardata

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Re: 1987 K75S no start, has spark & fuel
« Reply #8 on: December 31, 2015, 02:00:14 PM »
It sounds to me like your firing order is wrong.   

Double and triple check the plug wires that you have them on the correct plugs.  If I am not mistaken, the one for cylinder #3 is longer than the one for #2 and it is easy to get them mixed up. 

Also check to make sure your plugs have the "nut" that goes on the terminal, and that the plug cap is firmly pushed down on the plug.

aaannnndddd we have a winner!!!! Thanks for everyone who helped, it purrs like a kitten now. I'm going to get her all back together and on the road :)
  • Hartford, CT
  • 1987 K75S
1987 BMW K75S

Offline The Mighty Gryphon

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Re: 1987 K75S no start, has spark & fuel
« Reply #9 on: December 31, 2015, 02:44:43 PM »
Was it the firing order or missing terminal nuts?

Always good to hear that another one of these beauties is ready for the open road.

BTW, whereabouts Hartford?  My son is in Glastonbury.  Might have to try to meet up when I get out there.
  • In my garage in Marilla, NY
  • '91K100RS White/Blue
Current:
'91 K100RS16V "Moby Brick Too"

Past:
'94 K75RT "Ilsa, She Wolf of the SS"
'92 K100RS16V "Moby Brick" (RIP, deceased in a vehicular assault)
'94 K75S Special Edition Dakar Yellow "Cheetos"
'89 K100RS Special Edition "Special Ed"

Offline elementarydeardata

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Re: 1987 K75S no start, has spark & fuel
« Reply #10 on: December 31, 2015, 03:08:45 PM »
The plug wires were on the wrong plugs! It's a bit counter-intuitive, as the longest wire doesn't go to the farthest plug from the coil as I thought. I have no idea if I was the doofus who did it or if it came from the previous owner that way (he hadn't had it running in a while).

I'm in Simsbury, it's two towns north of the actual city of Hartford.
  • Hartford, CT
  • 1987 K75S
1987 BMW K75S

Offline K1300S

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Re: 1987 K75S no start, has spark & fuel
« Reply #11 on: December 31, 2015, 03:25:33 PM »
Was it the firing order or missing terminal nuts?

Always good to hear that another one of these beauties is ready for the open road.

BTW, whereabouts Hartford?  My son is in Glastonbury.  Might have to try to meet up when I get out there.

Geeez...small world. I lived in glastonbury (aka glastonboring) in junior and senior high school.
Project Thread "K75s Midlife Refresh"
http://www.motobrick.com/index.php/topic,7810.0.html

Offline The Mighty Gryphon

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Re: 1987 K75S no start, has spark & fuel
« Reply #12 on: December 31, 2015, 04:35:59 PM »
The plug wires were on the wrong plugs! It's a bit counter-intuitive, as the longest wire doesn't go to the farthest plug from the coil as I thought. I have no idea if I was the doofus who did it or if it came from the previous owner that way (he hadn't had it running in a while).

I'm in Simsbury, it's two towns north of the actual city of Hartford.

I'd rather not say how I found out that little thing about plug wires... 

Glastonboring...I hear ya.  LOL   Nice quiet town, bordering on depressing.  Nice place to raise kids though.
  • In my garage in Marilla, NY
  • '91K100RS White/Blue
Current:
'91 K100RS16V "Moby Brick Too"

Past:
'94 K75RT "Ilsa, She Wolf of the SS"
'92 K100RS16V "Moby Brick" (RIP, deceased in a vehicular assault)
'94 K75S Special Edition Dakar Yellow "Cheetos"
'89 K100RS Special Edition "Special Ed"

Offline Laitch

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Re: 1987 K75S no start, has spark & fuel
« Reply #13 on: December 31, 2015, 05:38:44 PM »
 :clap:
  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles

Offline escodsm

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Re: 1987 K75S no start, has spark & fuel
« Reply #14 on: January 17, 2016, 05:30:21 PM »
Fellow NorthEaster here - Rhode Island - we should plan a meet and ride summer 2016 if I ever get this K75 cafe running....mine is doing the same thing as in your video, But I made sure the plugs went to the matching coils (1st plug closest to front wheel == 1st coil closest to front wheel, etc)

The more I look at what my bike USED to look like (black S model with the belly fairing and tinted windscreen), the more I wish I had all those parts...but I shall finish my cafe project or else!!!
  • Providence, RI
  • 1987 K75 Projekt nackte Straßenmotorrad

Offline The Mighty Gryphon

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Re: 1987 K75S no start, has spark & fuel
« Reply #15 on: January 18, 2016, 10:40:50 AM »
Once you get all the wires going to the right plugs and the engine runs properly, take a Sharpie pen and write the cylinder number on the plug caps.   
  • In my garage in Marilla, NY
  • '91K100RS White/Blue
Current:
'91 K100RS16V "Moby Brick Too"

Past:
'94 K75RT "Ilsa, She Wolf of the SS"
'92 K100RS16V "Moby Brick" (RIP, deceased in a vehicular assault)
'94 K75S Special Edition Dakar Yellow "Cheetos"
'89 K100RS Special Edition "Special Ed"

Offline escodsm

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Re: 1987 K75S no start, has spark & fuel
« Reply #16 on: January 18, 2016, 06:31:13 PM »
But this is correct, right?

(1st plug closest to front wheel == 1st coil closest to front wheel, etc)
  • Providence, RI
  • 1987 K75 Projekt nackte Straßenmotorrad

Offline Laitch

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Re: 1987 K75S no start, has spark & fuel
« Reply #17 on: January 18, 2016, 07:37:38 PM »
Has this bike ever run since you've owned it, escodsm? Have you ever removed and replaced the spark plug HT leads? If you have, has it run since then?

  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles

Offline escodsm

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Re: 1987 K75S no start, has spark & fuel
« Reply #18 on: January 18, 2016, 11:38:59 PM »
Has this bike ever run since you've owned it, escodsm?

No.  I bought it as a parts bike, sight unseen, at the same time I bought my running K.  She was missing all the body work save the tank, which is all scratched up from having ski bindings run their aluminum teeth across the black paint, while the bike sat in the previous owner's barn. 
A family of furry mice decided to make the air box - and the space on the top side of the block near the coolant temp sensor - "home" by chewing through the plastic to connect the two areas.
The tires were rotted where they had sat flat on the soggy earth, for years.
The switches and controls on the handlebars were smashed and cables kinked by who the hell knows what kind of evil force awakened in that barn.

Then the decision was made.  I had so much fun on my other K, I decided this K should get another chance at life. 
I don't have much of a budget for this as I am a married father of 3 small ones, and there's priorities.  But, no rush. 

I've since replaced the entire harness, got 'new' tires (wouldn't ride on them, but they hold air), tried three starter relays, tested the coils, cleaned the starter, (installed starter incorrectly), re-installed the starter properly, and traced down a couple nasty electrical issues with great help from my father in law.  While I am doing this to my K project, he's over there on the other side of the garage putting his 69 BSA back together.  He's beaten me so far but has yet to put a chain on it...so there's still time!

Sorry for the long response, it's just a touchy question lol :musicboohoo:

Have you ever removed and replaced the spark plug HT leads?

No, the original wires are there coil to plug.  How many ohms am I looking for when I test 'em?

edit:added ohm question
  • Providence, RI
  • 1987 K75 Projekt nackte Straßenmotorrad

Offline Laitch

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Re: 1987 K75S no start, has spark & fuel
« Reply #19 on: January 19, 2016, 05:48:12 AM »
It may be helpful for you to start your own thread about this bike in the Projects section rather than keep hitchhiking on other threads. When you do, summarize what you've been through so far. That way some of us may keep up easier with your progress. Note the incoming wire color of each coil to the outgoing lead from that coil to its cylinder then compare your working bike's layout to your non-starter's. If your non-starter differs, make it the same.
  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles

Offline escodsm

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Re: 1987 K75S no start, has spark & fuel
« Reply #20 on: January 19, 2016, 07:35:00 AM »
You're correct, I apologize, my forum etiquette is lacking...I will start a new thread. 

Also I no longer have the running K bike, I thought I mentioned that but I did not. :falldown:
  • Providence, RI
  • 1987 K75 Projekt nackte Straßenmotorrad

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