Fuel Starvation Issue or what? '87 K75s

[kentuvman]

Pictures of Fuel Pump hoses

Double checked plumbing from fuel pump and from what I can see, all looks good. Long hose goes from fuel pump to one end of fuel filter. Second pic is short hose from fuel filter going into rail that appears to be rear nipple on fuel supply side.

New hose should arrive tomorrow - will post update!

 

[98lee]

Just checked the bikes in my shop. 1 '87 C, 1 '87 S, 3 '88 Ss, and 1 '93 S; ALL have the foam protective outer hose over the regulator return hose.

 

[8ninety8]

In thinking about foam insulator on return hose to lower fuel temp., has anyone mounted FPR and return hose outside throttle bodies? To keep fuel temp. down? Or is that too dangerous? Or am I over thinking?

 

[98lee]

See photo in post #54. The fact that the foam outer hose covers less than 20% of the return hose makes me more inclined to believe that it is more of a chafe guard than a heat insulator.

The act of pulling the tank back during removal causes the area that the outer hose is at to rub against the nearby frame. I think that is what it was designed to protect against.

 

[robsryder]

Just checked the bikes in my shop. 1 '87 C, 1 '87 S, 3 '88 Ss, and 1 '93 S ...

All red, I hope

 

[98lee]

All red, I hope

Rob,

Unfortunately the C and the '93 are blue. The C will go away as soon as I find time to put a clutch in it. I like Ss better.

 

[98lee]

All red, I hope

Unfortunately the C and the '93 are blue. The C will go away as soon as I find time to put a clutch in it. I like Ss better.

 

[kentuvman]

Making Progress - Not Out of the Woods Yet

OEM fuel hose from fuel pressure regulator to front of fuel tank arrived and installed today. A noticeable difference than the hose that was on previously - like perfect bends where it attaches to the FPR and fuel tank!

Bike started - no leak - ran like crap - like she barely ran.

Thought about Air Box and the Air Flow Meter.

Just went to check to make sure I'd oriented the air filter properly as Clymer book shows writing on air filter directly beneath lid but in reality it is oriented so writing is at back of air box (see picture below).

BTW - orienting that hose is ridiculously difficult! Loosened clamp that attaches to box where fuel meter is but couldn't get it to move and not wanting to break anything, left it alone.

Thought I had air box male hose clamped securely to the hole in air intake above throttle bodies but no - it wasn't secured at all when I went to check the filter.

I'll ask a friend to help me orient hoses so I can secure

It's quite possible that besides the fuel smell I'd been having at beginning of thread had to do with injectors or a hose that was starting to go (which it did) and the idle problem because the connection points weren't air tight introducing unmetered air.


Getting close . . .

 

[98lee]

Yeah, if that large 90 degree hose is not properly connected to the plenum over the throttle bodies the bike either will not run or run like crap. When connecting that hose to the plenum, the filter must be removed. Insure that the screw for the clamp is to the rear of the hose and pointed up for easy access.

The second picture caused me to rethink that larger diameter foam hose around the regulator return hose. I think it is probably more likely that it's purpose is to insulate the fuel line from the heat of the coolant stand pipe and the coolant hoses coming off of it. The coolant typically runs in the 180-220 degree range which is within the boiling point of gasoline so it would be important not to have the fuel line touching the stand pipe which would easily transfer the the coolant heat to the fuel hose. The coolant hoses would also transfer the heat, but probably to a slightly lesser degree. So I think that is probably a better guess as to the purpose of the outside hose.

 

[kentuvman]

Yeah, if that large 90 degree hose is not properly connected to the plenum over the throttle bodies the bike either will not run or run like crap. When connecting that hose to the plenum, the filter must be removed. Insure that the screw for the clamp is to the rear of the hose and pointed up for easy access.

Good Info Lee - my approach/technique was assembling filter, clamping box together and then trying to line up the 90 degree hose to plenum - will adopt your suggestion above - really appreciate your involvement here! Thank You!

 

[98lee]

That explains your difficulty. Before doing the finish tightening of the hose clamp, push the airbox lid as high as it will go up against the frame and wiring, as that will be it's normal position. If tightened when hanging down against the bottom of the air box, it will have to twist to get to it's final position and that would promote cracking.

I belive that the end of the hose that connects to the air flow meter has an indexing notch that prevents it from rotating. I'll check.

 

[98lee]

Just went to check to make sure I'd oriented the air filter properly as Clymer book shows writing on air filter directly beneath lid but in reality it is oriented so writing is at back of air box (see picture below

I just deleted my previous post on this subject after going out to the shop and actually looking. The only way the factory filter goes in is with the writing going towards the rear of the bike (or on your left as you slide it in). There is no lip on the side of the filter that slides in first (on the throttle body side of the filter) to make it possible to slide in with the limited clearance that is available. Make sure the arrow points UP!

There are SOME (I believe the very early ones) factory and aftermarket filters that don't have the deep lip around the filter that could also be installed with the writing towards the front of the bike.

 

[98lee]

I belive that the end of the hose that connects to the air flow meter has an indexing notch that prevents it from rotating. I'll check.

Confirmed!

 

[98lee]

The second picture caused me to rethink that larger diameter foam hose around the regulator return hose. I think it is probably more likely that it's purpose is to insulate the fuel line from the heat of the coolant stand pipe and the coolant hoses coming off of it. The coolant typically runs in the 180-220 degree range which is within the boiling point of gasoline so it would be important not to have the fuel line touching the stand pipe which would easily transfer the the coolant heat to the fuel hose. The coolant hoses would also transfer the heat, but probably to a slightly lesser degree. So I think that is probably a better guess as to the purpose of the outside hose.

After going out to the shop and looking at the one bike that doesn't have bodywork on it, I feel even stronger that the purpose and location of the outer hose is as above.

 

[kentuvman]

She Runs Like a Jet!

Wouldn't you know it, here is post #75 - is this a coincidence? I think not!

Got the air box mounted properly today thanks to Lee sharing how he does it and she started right up.

Just got back from a 35 mile ride - now @ 57 degrees but colder due to wind chill so fingers a little stiff!

Thanks to this the wonderful sharing from this group, I'm bearing the fruits of my labor.

She's running unbelievably well - good idle, no hesitation, super quick - what can I say other than . . .


T H A N K Y O U A L L V E R Y MUCH !

 

[98lee]

Way to go Ken!

I think the maintenance and mods that you did will help keep your brick flying for a long time to come.

 

[robsryder]

The plastic handguards for the R100GS will fit perfectly on the K75S. These handguards do a very nice job of keeping much of the cold air off one's hands. [Heated gloves don't hurt either].

On my 88 K75S I replaced the 55 Watt main headlight bulb with a 20 Watt LED bulb and also added two 10 Watt LED driving lights (attached to fork legs using the bolt holding the fender in place). This LED configuration takes only 40 Watts vs 55 Watts with the stock incandescent bulb and provides a lot more light.

I rode my 88 K75S to the RA rally in Arkansas recently and it got a bit chilly. I decided to get a heated jacket liner and heated gloves while there. It was very nice to have and I was glad of having gone to the LED lights.

LED lights can be obtained from -

https://www.superbrightleds.com/mor...-with-flexible-tinned-copper-braid/2221/4993/
https://www.superbrightleds.com/mor...aux-2in-modular-led-off-road-work-light/1699/

http://stores.advmonster.com/headlight-replacement/
http://stores.advmonster.com/led-lights/

 

[kentuvman]

Way to go Ken!

I think the maintenance and mods that you did will help keep your brick flying for a long time to come.

Additionally, I balanced the throttle bodies with my CarbMate - they were not in sync but are now - deceptive because she ran pretty well as-is but now so much better - really better! The dominant throttle body was where the vacuum hose connects and then I balanced each throttle body to it.

 

[kentuvman]

The plastic handguards for the R100GS will fit perfectly on the K75S. These handguards do a very nice job of keeping much of the cold air off one's hands. [Heated gloves don't hurt either].

On my 88 K75S I replaced the 55 Watt main headlight bulb with a 20 Watt LED bulb and also added two 10 Watt LED driving lights (attached to fork legs using the bolt holding the fender in place). This LED configuration takes only 40 Watts vs 55 Watts with the stock incandescent bulb and provides a lot more light.

I rode my 88 K75S to the RA rally in Arkansas recently and it got a bit chilly. I decided to get a heated jacket liner and heated gloves while there. It was very nice to have and I was glad of having gone to the LED lights.

LED lights can be obtained from -

https://www.superbrightleds.com/mor...-with-flexible-tinned-copper-braid/2221/4993/
https://www.superbrightleds.com/mor...aux-2in-modular-led-off-road-work-light/1699/

http://stores.advmonster.com/headlight-replacement/
http://stores.advmonster.com/led-lights/

Hi Rob - interested to see a pic of your lights on your bike - my headlight came with the modulating feature and I've got some heavy duty driviing lights mounted on the forks. Don't think the hand guards will work as I've got "S" Bars with a Parabellum Windscreen and bar end mirrors.

 

[robsryder]

Here are a couple of photos of LED running lights attached to forks -