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1990 K75S fuel line routing?

scottishsg

scottishsg

New member
Hey all, after a hiatus for another injury recovery.......I am starting to put the rest of the K back together!!
Does anyone have, or be willing to take pics of the routing for fuel lines under tank? There are 2 on the left side of thank, obviously the feed and return lines. I just need to know if the forward line goes to fuel rail and the rearward one is the return? Or vice versa. Then on the under side, more to right side, there are two skinny pipes sticking out. Are these suppose to have lines attached? Do they remain open as some sort of breather?
Thanks as always for any assistance you folks may provide. This maybe the longest K75 repair in history!!
 
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Left side forward is the return from the fuel pressure regulator.

Left side rear goes to fuel rail.


Small right side front is the tank breather that, on US smog bikes, went forward through a check valve and into the crankcase just below the fan.

Small right side rear is the fuel filler rain drain that drains through a hose to behind the right peg plate.

Non US bikes (and US owners that think extra gas vapor in the oil is less than desireable) use " the cup" or, as BMW calls it, the Air Accumulator: 16 13 2 307 467 AIR ACCUMULATOR $2.56 . The cup attaches to the frame below the two small nipples on the right side. The hose that used to go to the rain drain now hooks to the cup drain. The nipple on top of the crankcase under the fan must be capped.




:dance:dance:dance
 
Thanks Lee! I do appreciate it. I see the cup, It has a hose attached to it, I assume it just gets zip tied to the frame behind the right leg plate somewhere? The two thin ports on tank just stay open and drain into the cup. I should have this old girl running tomorrow!!
 
Make SURE that the nipple on top of the block, below the fan, is securely capped!




:dance:dance:dance
 
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The nipple is secure! I am about to put fuel in and fire her up. Prior to doing so I wanted to make sure all is well. I turned key on, but I did not hear pump priming? Is this normal? Should there be an audible buzz?
 
scottishsg said:
The nipple is secure! I am about to put fuel in and fire her up. Prior to doing so I wanted to make sure all is well. I turned key on, but I did not hear pump priming? Is this normal? Should there be an audible buzz?
Click to expand...

No. Oilhead pumps run a few seconds when the key is turned on. K75s do not. The pump first energizes when the starter button is pressed.
 
Thanks Paul! I put fuel in and it cranks no start. Hasn't ran in 10 years so not sure exactly what's going on now. Will need to do some investigating.
 
scottishsg said:
Thanks Paul! I put fuel in and it cranks no start. Hasn't ran in 10 years so not sure exactly what's going on now. Will need to do some investigating.
Click to expand...

Open the fuel cap and with your ear to the opening turn on the key and just stab the start button - not long enough to really crank - just long enough to energize the circuit. You should then hear the pump in the tank run for a few seconds.
 
Thank you, I had just checked that and nothing. I have only 9ish Volts getting to power side of pump. It is maybe the pump relay?
 
With the fuel pump relay out, I have continuity between pins 85 & 86 and also continuity between pins 87 & 87a? 85 and 86 are coil so that sounds right but 87 and 87a should not be joined right? At rest I though 87a should be joined to 30. When energized it would be 30 and 87 joined. It has a type A relay in there, I hope that is the correct one? Does any of this make sense?? Thanks for any insight you be able to provide!
 
scottishsg said:
With the fuel pump relay out, I have continuity between pins 85 & 86 and also continuity between pins 87 & 87a? 85 and 86 are coil so that sounds right but 87 and 87a should not be joined right? At rest I though 87a should be joined to 30. When energized it would be 30 and 87 joined. It has a type A relay in there, I hope that is the correct one? Does any of this make sense?? Thanks for any insight you be able to provide!
Click to expand...

I doubt the relay is bad. They seldom deteriorate just sitting. Fuel pumps do get gummed up. If you don't hear the pump run then remove it and bench test it directly, outside the tank where you can apply power directly to the pump.
 
The pump is not gummed up, it's brand new from BMW. I just put first load of fuel in to try and start the bike. I do have battery voltage to the relay but only 9v to the pump. So either relay is bad or circuit to pump is high resistance. I have a relay tester at work so I will test it tomorrow. If it's good I will remove pump and bench test it. Just because it's a new part doesn't mean it's a good part. If it fires up I'll the test circuit from pump back to relay for corrosion or cross short somewhere. Ugh I was looking forward to it starting......
 
Pump ran fine outside the bike. Took relay apart and cleaned it and pump fired up. Put everything back together and she started right up after about 4 seconds of cranking! Now.....I have red warning triangle light on and a fair amount of blue smoke. Seems like the smoke was getting progressively worse as it warmed up. Do K bikes have valve stem seals? I will do a compression check during the week if I can remember to bring my gauge home.
 
The warning triangle is your bulb check warning light. After you start the bike, you must activate the front brake and rear brake (in any order). The system will check your front and rear brake light switches, brake light bulb and tail light bulb. If any of those are bad, the will stay on. If they are all functioning, the light will go out.

As for the smoke, try riding around the block several times or ride for a couple miles. It should go away. Trying to get it to go away sitting still usually doesn't work well. It is usually oil that has gotten past the rings while sitting on the side stand.



:dance:dance:dance
 
Thanks again Lee! Turns out I didn't plug in the tail lamp assembly, so I will take care of that during week. Rode the bike and it died. Seems that either the fuel pump relay is bad or the pins where it plugs in are loose. I can tap on the relay and get it started again. Unfortunately it's a silly unconventional relay so I'll order a new one from BMW and clean/tighten the pins and see what happens. Seems that the smoke will be there one start up and not the next then back again lol. This bike will definitely be a learning curve!
 
Very briefly while I get off and pull it onto center stand. I've heard it can be better to lean to right and then shut it off?
More pressing though is figuring out why the fuel pump is shutting off. I may just run all new wires from the relay box to fuse to pump. Then I don't need to worry about loose connection any more.
 
Ok then.....I've found that if I prop the rear of the tank up about 4 inches the fuel pump will run no problems at all. As soon as I lower the tank the pump shuts off. I'm going to pull the tank all the way off again and look at the wiring. Obviously it has either broken wire or loose connector. Is there something common should check for first?? Thanks again for any help!!!
Incidentally....is there a market for selling them bikes? Ill health is going to force me to sell it soon I think. Would love to have it running well first though.

Sent from my LG-H820 using Tapatalk
 
Sounds like you have a poor connection at the tank plug or where the wires go through the bottom of the tank. http://forums.bmwmoa.org/showthread.php?72833-Fuel-Tank-Pump-Level-Sensor-Wiring-All-Early-Kbikes Either one would also explain the voltage drop.

As for the smoking, shut off bike,THEN lean bike to the right for around twenty seconds to allow the oil that is in the cylinders below the pistons to drain into the crankcase.

A good running K75S in good cosmetic shape should not be hard to sell at all. It is still recognized as a very good bike.



:dance:dance:dance
 
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