K75 Fuel delivery problem - K-Bikes.com - Excellence in Motion
 
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post #1 of 9 (permalink) Old Jan 27th, 2011, 12:42 pm Thread Starter
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Location: Sugar Land, TX, USA
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Question K75 Fuel delivery problem

I am a new member and this is my first post. Bought a non-running 1987 K75 yesterday to resurrect and accompany my other German machines (BMW R80 Airhead and 72 911 EFI 2.7L).

According to the previous owner this bike has not run in 3 years. At that time the bike simply stopped running while going down the road. So far, sparkplugs fire but there is no fuel pressure. There is no elect resistance across the + and - on the fuel pump (i.e. potential short)... with key on only, no response from pump and no elect signal to pump... with key on and starter turning 10 volts measured on pump terminals but unable to hear pump due to sound from starter. Jumped 12.8 volts (from separate power supply) across pump and pegged amp meter at 8 Amp max/limit momentarily while hearing the dreaded buzz from pump. I assume the pump is toast but want to know for sure before replacing it.

Will appreciate input from members familiar with kbikes:
Is it common for the fuel pump to fail? (stop abrubtly while riding)
Are there other tests to perform to confirm pump is bad?
Any tricks on reviving the existing pump? (shock it, disassemble it, pressurize it)
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post #2 of 9 (permalink) Old Jan 27th, 2011, 3:31 pm
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Sounds like the pump is toast. Some folks have soaked the pump in acetone and freed it up. Try soaking for a day or so then if it still won't turn, alternate polarity for short bursts and it what that does.

Ron Cooper

91 K75RT
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post #3 of 9 (permalink) Old Jan 27th, 2011, 9:03 pm
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Welcome. Since you are new to K-bikes you may not have heard that some folks have used non-bmw fuel pumps successfully. Here is one link about it: http://www.ibmwr.org/ktech/fuel-pump-install.shtml

Here is another link as well: http://k11og.org/forum/viewtopic.php?t=6454

Last edited by WayneDW; Jan 27th, 2011 at 9:24 pm.
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post #4 of 9 (permalink) Old Jan 28th, 2011, 12:16 am
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fuel delivery

Sounds like the same problem I had when I purchased a K100 that hadn't been run in over 6 years. I removed the fuel in the tank and then pulled the fuel filter out. I couldn't blow through it as it was completely plugged up. I removed the pump and flushed it out in a kerosene bath. It fired right up and has worked fine ever since. I steam cleaned the tank as it was full of crap left over from the gas (pepsi-cola) being in it for many years. I then removed the injectors, checked continuity, and replaced the o-rings on both ends. I am going to send them out to get cleaned later this spring. You can put everything back together and fire the injectors out of the bike if you want. Install them last. Aim them onto a towel and hit the starter. You can see them working which should solve your problem. Don't be afraid to get into the bike. That's how you learn. If you get stumped, your answers are here from somebody who has experienced the same problem. Lots of solutions here from some pretty knowledgeable guys...........
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post #5 of 9 (permalink) Old Jan 28th, 2011, 9:07 pm Thread Starter
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Hurray!!! Replaced the fuel pump and she fired on the first press of the starter button... I am impressed with this bike already. Thanks to all of you posters for the help. I appreciate it very much.

Due to budgetary restraints i opted for the aftermarket pump. Also built a linkage off of the bottom of the pump extending it about an inch and a half deeper into the tank. A 3/4 copper water pipe fit perfectly into the nylon mesh filter supplied with the pump so i cut off about a 1/2 inch piece to fit in properly leaving about half of it protruding. A 3/4 copper union was within about 1/32 from fitting over bottom of the pump intake so i removed this amount from the inner wall of the union using a lathe for a perfect fit. After fitting the filter - to the pipe - to the union -to the pump and testing that it all fit in the gas tank... I drilled and tapped 4mm allen head SS screws to hold it together permanently. Here is a pic of the assembly to help illustrate.

[IMG]Hurray!!! Replaced the fuel pump and she fired on the first press of the starter button... I am impressed with this bike already. Thanks to all of you posters for the help. I appreciate it very much.

Due to budgetary restraints i opted for the aftermarket pump. Also built a linkage off of the bottom of the pump extending it about an inch and a half deeper into the tank. A 3/4 copper water pipe fit perfectly into the nylon mesh filter supplied with the pump so i cut off about a 1/2 inch piece to fit in properly leaving about half of it protruding. A 3/4 copper union was within about 1/32 from fitting over bottom of the pump intake so i removed this amount from the inner wall of the union using a lathe for a perfect fit. After fitting the filter - to the pipe - to the union -to the pump and testing that it all fit in the gas tank... I drilled and tapped 4mm allen head SS screws to hold it together permanently. Here is a pic of the assembly to help illustrate.
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post #6 of 9 (permalink) Old Jan 28th, 2011, 9:21 pm
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Pictures didn't come through. Congrats on getting it running. I suggest you check the driveshaft splines before you ride it much.

Ron Cooper

91 K75RT
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post #7 of 9 (permalink) Old Jan 29th, 2011, 9:37 am
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Excellent!
I'm curious as to which pump you used and where you got it.
Please try again to post the picture.
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post #8 of 9 (permalink) Old Feb 3rd, 2011, 6:51 pm Thread Starter
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The fuel pump pic

Here is the fuel pump pic. The s/s hose clamp snugged around the pump insures pump doesn't slip down.

I pulled the driveshaft; splines and grease looked good to me but you never know until you take a look. Cleaned off the old grease and went back with mobil 1 synthetic red.

I have attached the pic as a file attachment this time. I am going to need some instruction to attach it as an image in the text area here.
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post #9 of 9 (permalink) Old Feb 3rd, 2011, 9:08 pm
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[QUOTE=fdalgas]I pulled the driveshaft; splines and grease looked good to me but you never know until you take a look. Cleaned off the old grease and went back with mobil 1 synthetic red.

The driveshaft splines need a grease with MOLY content. Honda MOLY 60 and GUARDDOG 525 are good ones. Regular grease won't hold up.

Thanks for the pics of your pump-well done.

Ron Cooper

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