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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: RZRob on April 15, 2020, 07:57:58 PM

Title: My K75S Runs for a few minutes - Fuel Pump Issue
Post by: RZRob 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
Title: Re: My K75S Runs for a few minutes - Fuel Pump Issue
Post by: johnny 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
Title: Re: My K75S Runs for a few minutes - Fuel Pump Issue
Post by: RZRob 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
Title: Re: My K75S Runs for a few minutes - Fuel Pump Issue
Post by: johnny 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
Title: Re: My K75S Runs for a few minutes - Fuel Pump Issue
Post by: RZRob 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
Title: Re: My K75S Runs for a few minutes - Fuel Pump Issue
Post by: Filmcamera 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
Title: Re: My K75S Runs for a few minutes - Fuel Pump Issue
Post by: 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.
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Title: Re: My K75S Runs for a few minutes - Fuel Pump Issue
Post by: 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
Title: Re: My K75S Runs for a few minutes - Fuel Pump Issue
Post by: beemuker 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.
Title: Re: My K75S Runs for a few minutes - Fuel Pump Issue
Post by: Paul_Waterloo 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 676 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.
Title: Re: My K75S Runs for a few minutes - Fuel Pump Issue
Post by: Martin 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.
Title: Re: My K75S Runs for a few minutes - Fuel Pump Issue
Post by: volador on April 17, 2020, 12:17:07 AM: Easter Beaver Sumitomo TS090 Sealed Connectors (http://easternbeaver.com/Main/Elec__Products/Connectors/Sealed/SMTS/smts.html)

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
Title: Re: My K75S Runs for a few minutes - Fuel Pump Issue
Post by: Paul_Waterloo on April 17, 2020, 07:52:13 AM: Great, bought two of them.
Title: Re: My K75S Runs for a few minutes - Fuel Pump Issue
Post by: RZRob on April 18, 2020, 02:05:39 AM: (https://scontent-lax3-2.xx.fbcdn.net/v/t1.0-9/91212663_10157566055234405_2104246023252606976_o.jpg?_nc_cat=106&_nc_sid=07e735&_nc_ohc=OhMLsZd4bKEAX9sFOk9&_nc_ht=scontent-lax3-2.xx&oh=4ebc1cb01398ff9c1e3b26dc5f394b24&oe=5EC05E03) 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
Title: Re: My K75S Runs for a few minutes - Fuel Pump Issue
Post by: 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.
Title: Re: My K75S Runs for a few minutes - Fuel Pump Issue
Post by: stokester 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 (https://www.motobrick.com/index.php/topic,12347.msg109228.html#msg109228)
Title: Re: My K75S Runs for a few minutes - Fuel Pump Issue
Post by: RZRob 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