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Author Topic: My K75S Runs for a few minutes - Fuel Pump Issue  (Read 6221 times)

Offline RZRob

  • Motobrick Curious
  • Posts: 10
My K75S Runs for a few minutes - Fuel Pump Issue
« on: April 15, 2020, 07:57:58 PM »
Hi folks,

I recently picked-up an '87 K75S that had been sitting for years. The fuel pump and sender unit had decomposed to a blob. I replaced both and the bike started fairly quickly and after a few minutes the bike ran like it had no issues. I went an a 5 mile trek around my neighborhood. No problems.

A few days later I went to take it for a ride. It started and ran a total of about 5 minutes then sputtered to a stop. I pulled over and pondered life cycled the key a few times and it started right up and ran for another few minutes. This seems to be a predictable repeatable consistent issue. Upon inspection it seems like the fuel pump is NOT running when the bike dies, and until I wait a couple minutes, nothing will make the pump cycle.

Any ideas?

RZ Rob
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  • California
  • '87 K75 RS

Offline johnny

  • TrailBrakingThrottleWhacker
  • ^ Quintessential Motobricker
  • Posts: 7653
  • Whacking...n...Chopping Sliding...n...High Siding
Re: My K75S Runs for a few minutes - Fuel Pump Issue
« Reply #1 on: April 15, 2020, 08:09:48 PM »
greetings...

4 pin... needs mystery oil techron no corn ethyl lotts of red line miles... plus all new rubbers...

dont take it to irv severs... take it to liors...

https://liorsmotoride.godaddysites.com/

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

Offline RZRob

  • Motobrick Curious
  • Posts: 10
Re: My K75S Runs for a few minutes - Fuel Pump Issue
« Reply #2 on: April 15, 2020, 08:14:26 PM »
I barely understand. I did add some Techron before taking it out today. What do you mean b y new rubbers. Bike runs great while the pump is pumping. I tend to be hard on the throttle within reason. But it'll just all of the sudden sputter out and stop until I pull over and sit a couple minutes.

RZ Rob
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  • California
  • '87 K75 RS

Offline johnny

  • TrailBrakingThrottleWhacker
  • ^ Quintessential Motobricker
  • Posts: 7653
  • Whacking...n...Chopping Sliding...n...High Siding
Re: My K75S Runs for a few minutes - Fuel Pump Issue
« Reply #3 on: April 15, 2020, 08:16:30 PM »
greetings...

post up some photos of this moto...

ok then... start with the 4 pin...

its #3 here...

http://www.motobrick.com/index.php/topic,11033.0.html

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

Offline RZRob

  • Motobrick Curious
  • Posts: 10
Re: My K75S Runs for a few minutes - Fuel Pump Issue
« Reply #4 on: April 15, 2020, 08:19:53 PM »
This is the part I don't understand. What do you mean by 4-pin? Are you mentioning something about the plug for the sender unit? Please elaborate.

RZ Rob
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  • California
  • '87 K75 RS

Offline Filmcamera

  • ^ Quintessential Motobricker
  • Posts: 1483
Re: My K75S Runs for a few minutes - Fuel Pump Issue
« Reply #5 on: April 15, 2020, 08:51:21 PM »
The dreaded 4-pin is the connection from the loom to the fuel pump.  It is a 4-pin connector (hence the name - catchy huh?) on the RHS side of the bike near the rear of the tank.  They are famous for playing up.  Find it, unplug it, clean the heck out of it and connect it again.  If it dies on the road just unplug and plug it again a few ties ad it should start working (mine always does)


Many members have also replaced the oem 4-pin connector with a new waterproof one to fix the issue.


Good luck
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  • San Jose, Costa Rica
  • 1991 K100RS 16v ABS1, 2022 Triumph Tiger 900 Rally Pro
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Offline Martin

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Re: My K75S Runs for a few minutes - Fuel Pump Issue
« Reply #6 on: April 15, 2020, 10:10:20 PM »
As Jo and FC stated known problem, so save yourself a lot of aggravation replace it with a good brand waterproof one from your local electronics store. Picture is of an aftermarket one.
Regards Martin.

* Four Pin connector.jpg (52.14 kB . 512x384 - viewed 674 times)
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  • North Lakes Queensland Australia
  • 1992 K75s Hybrid, Lefaux, Vespa V twin.
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Offline RZRob

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  • Posts: 10
Re: My K75S Runs for a few minutes - Fuel Pump Issue
« Reply #7 on: April 15, 2020, 10:17:37 PM »
I totally believe this is what's going on.

I'll investigate and report.  Pics to follow.

RZ Rob
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  • California
  • '87 K75 RS

Offline beemuker

  • ^ Quintessential Motobricker
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Re: My K75S Runs for a few minutes - Fuel Pump Issue
« Reply #8 on: April 16, 2020, 04:21:27 PM »
Quote from: RZRob on April 15, 2020, 10:17:37 PM
I totally believe this is what's going on.

I'll investigate and report.  Pics to follow.

RZ Rob
I hope you are right, but belief will only take you so far. But might as well start with the easy fixes.
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  • Panama City, FL
  • '00 R1100RT,’92 K75 RT,past tense:'83 R80ST, '93 K1100LT,,94 R1100RS K75s, Honda NC700, Suzuki Bandit 1200, bmw R75/5 Honda 750

Offline Paul_Waterloo

  • ^ Motobrick Curious
  • Posts: 73
Re: My K75S Runs for a few minutes - Fuel Pump Issue
« Reply #9 on: April 16, 2020, 09:15:00 PM »
Quote from: Martin on April 15, 2020, 10:10:20 PM
As Jo and FC stated known problem, so save yourself a lot of aggravation replace it with a good brand waterproof one from your local electronics store. Picture is of an aftermarket one.
Regards Martin.

* Four Pin connector.jpg (52.14 kB . 512x384 - viewed 674 times)

Do you know where to find a connector like that on the web, I quickly searched, but couldn't find anything. I like the looks of it.
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  • Chicago
  • 1993 K110LT, 2003 K1200GT

Offline Martin

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Re: My K75S Runs for a few minutes - Fuel Pump Issue
« Reply #10 on: April 16, 2020, 09:30:53 PM »
Your local electronics store should be able to help you. Alternatively go to Ebay and search for 4 pin waterproof connector.
Regards Martin.
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  • North Lakes Queensland Australia
  • 1992 K75s Hybrid, Lefaux, Vespa V twin.

Offline volador

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  • Posts: 1167
  • NEEDS MORE CHROME
Re: My K75S Runs for a few minutes - Fuel Pump Issue
« Reply #11 on: April 17, 2020, 12:17:07 AM »
Easter Beaver Sumitomo TS090 Sealed Connectors

the 'Sumitomo Not in Catalog Male 4P Connector'  3/4 of the page down looks very similar discreet connector

I get extra pins and seals
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  • NYC NY
  • 1991 K100RS 1993 K75S ABS
5 BOROUGHS SISYPHEAN SOCIETY  MAINTAINING THE OBSESSION

Offline Paul_Waterloo

  • ^ Motobrick Curious
  • Posts: 73
Re: My K75S Runs for a few minutes - Fuel Pump Issue
« Reply #12 on: April 17, 2020, 07:52:13 AM »
Great, bought two of them.
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  • Chicago
  • 1993 K110LT, 2003 K1200GT

Offline RZRob

  • Motobrick Curious
  • Posts: 10
Re: My K75S Runs for a few minutes - Fuel Pump Issue
« Reply #13 on: April 18, 2020, 02:05:39 AM »



I saw my 4-pin in the factory harness was corroded. I distorted the female side and cleaned them. The male side was new. Bike runs well.

RZ Rob
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  • California
  • '87 K75 RS

Offline Martin

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Re: My K75S Runs for a few minutes - Fuel Pump Issue
« Reply #14 on: April 18, 2020, 02:25:47 AM »
Replace it with the waterproof one while you have the time. The OEM one will fail again in the most inconvenient moment.
Regards Martin.
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  • North Lakes Queensland Australia
  • 1992 K75s Hybrid, Lefaux, Vespa V twin.

Offline stokester

  • ^ SuperNatural Motobricker
  • Posts: 850
Re: My K75S Runs for a few minutes - Fuel Pump Issue
« Reply #15 on: April 18, 2020, 06:04:15 PM »
Quote from: Martin on April 18, 2020, 02:25:47 AM
Replace it with the waterproof one while you have the time. The OEM one will fail again in the most inconvenient moment.
Regards Martin.
I have some to share.
https://www.motobrick.com/index.php/topic,12347.msg109228.html#msg109228
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  • Yorktown Virginia
  • '94 K75S Dakar Yellow - '93 K75S Seiden Blau - '91 R100RT Bermuda Blue- '78 R100S Smoke Red

Offline RZRob

  • Motobrick Curious
  • Posts: 10
Re: My K75S Runs for a few minutes - Fuel Pump Issue
« Reply #16 on: April 19, 2020, 10:46:44 AM »
Hi Stokester. I'll donate $10 if that's what you had in mind. If not, let me know and let me know how to donate.  I'd like to upgrade these connectors on my bike.

Robert Covington
7870 E. Menton Ave.
Anaheim, CA 92808
7l4-264-862l

RZ Rob
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  • California
  • '87 K75 RS
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