fuel line routing question

[diversity48]

Here's an excellent example of why pictures should be taken whenever a teardown is done:
Do you have your bike apart at the moment and, if so, could you take a picture of the correct routing of the hoses off the fuel pressure regulator? I have been waiting for parts for my 85 k100rs for a while, and now that I have the parts, I can't remember for the life of me what the order of the hoses is. I know the top one goes to the fuel tank, the bottom one is a vacuum line to a vac connection near the fuel rail. The one that stumps me is the connection facing the rear of the bike. I think it should go to the fuel rail but can't find a spot to connect it. Maybe someone with a clear memory, picture, or just the knowledge can come to my rescue? Would be nice to get this puppy on the road again. I said when I joined this forum I would have dumb questions, so here's example #1. :dunno

[Scott_]

I've got my '97 1100 on the table at the moment waiting to finish lifter adjustments. I could take some pics tomorrow unless someone else has some already.

IIRC fuel pressure line(rear) from tank, to rear(nipple pointing up) of fuel rail, front(nipple pointing down) of fuel rail to pressure regulator, pressure regulator back to tank.
Mine does not have vac control on the regulator as BMW did away with that on the 1100's but I would think that the rest of the fuel line routing should be the same.

[rbm]

[diversity48]

thanks, scott and rbm for the prompt replies! the picture shows sorta what I thought...I think I can take it from here...THANKS again for the help!

[Freelancer]

Rbm, has set ya right.

  The reason I'm posting is because of a mod I did. While your in there, it is pretty easy to relocate the pressure regulator to the outer side of the throttle bodies.

You unscrew it and pull it out. Put the screws back on and you are done on the inside area.
( If you have access to someone with skinny arms you don't even have to remove the air box. :2thumbup:)

Then you take the mounting plate off of the regulator and put the mounting plate in a vice.

The plate is soft untempered metal, so you can cut along the 90 degree angle that the regulator bolts to. Then bend the it to were it is straight. This allows it to clear the fuel rail when set right.

Loosely re-attach the regulator and then test fit the mount on the outside using the screws directly opposite of the inside ones.

When set right, the vacuum hose will face the front of the bike and the inlet from the fuel rail will point out and down. The fuel tank return outlet will point towards the back and slightly up.
 
The hose will run along the fuel rail and will run parallel to the fuel supply line right back up to the tank.


Why do this you ask?

Makes fuel line maintence much much easier and stopped the hot fuel tank problem because the regulator is no longer baking in a dead air pocket, right behind the radiator.
Will try to take pics of my mount soon.

Oh yeah, there is a rubber line you can get that the fuel hoses fit inside of. This helps insulate the fuel lines from heat and damage. Also can provide anti-kink support for tight turns in fuel line.

Later,
Freelancer

[Freelancer]

Here are the pic's I promised. They are the attach/links at the bottom.

*Note-For those pf you who don't want to download these, they are also posted in community forums "Heat" thread with some details as to how and why. :2thumbup: .....(don't understand why these are showing up different than the other posts????)

Have any questions about this, ask away.


Freelancer

[Freelancer]

I owe the community an apology. The FPR relocation as I have mine is not a full fix. The following is a quoted description of when and the conditions that caused the hot tank and an apology.

This is from the "Heat" thread in the Community center section:

Well, the FPR relocation is not as complete of a fix as I had thought.
Got the ol' warm feeling today while stuck in 1st gear stop&go traffic.

Temp was beyween 94°-96°F and I had 3/4 full tank. Had 45 minutes of normal town and highway traffic then hit a no exit construction area with near dead stop traffic.
 After 30 minutes of creeping along at idle in 1st & 2nd gear, the tank started feeling warm through the jeans.  :swear:

Up until the bottleneck the temp was fine and once I got back up to highway speed she eventually cooled back down. *Note-The tank never got as hot as it used to....but it got warm enough.

So, as it stands, The FPR relocate as I've done mine is definitely an improvement but not a perfect fix. The tank used to get hot at highway speeds, but haven't had that problem for a year.  The tank also cooled back down after I got going again.

So, I apologize if I mislead anyone with my earlier claim that the FPR relocation was a full fix/cure for the problem.


My next attempt at fixing this will probably involve a lower airbox delete. Then a smaller drycell battery laid on its side and a fan to help pull the hot air "through" the newly created open area. Basic idea is to give the hot air some place to go by venting it into the rear wheel low pressure zone.

Let me know what you guys think


Again, sorry for my error,
Freelancer

[woodgeek]

Does the direction of the connection matter for the fuel rail and the fuel pressure regulator matter? A fuel rail is just a pressurized plenum for the fuel. So “in” and “out” should be interchangeable. Is the flow of fuel through the regulator directional? I’ve never seen a cutaway of one but it would seem to be flow direction agnostic.


I’d like to relocate my FPR and this would simplify things.

[rbm]

I'm not sure that the direction of fuel in the rail matters because the same rail design is used on the 2V and 4V K-bikes yet, on a 2V K-bike, the fuel delivery is on the left side and exhaust the right side and it's opposite on a 4V K-bike.  That's my observation and maybe there's a really good reason the 4V K-bikes reversed the connections to the rail.

The direction of flow through the regulator is unidirectional on the otherhand.

[woodgeek]

I'm not sure that the direction of fuel in the rail matters because the same rail design is used on the 2V and 4V K-bikes yet, on a 2V K-bike, the fuel delivery is on the left side and exhaust the right side and it's opposite on a 4V K-bike.  That's my observation and maybe there's a really good reason the 4V K-bikes reversed the connections to the rail.

The direction of flow through the regulator is unidirectional on the otherhand.

Thanks! [emoji106]

[The Mighty Gryphon]

I agree that the direction has little or no bearing on operation.  Considering cross sectional area and flow rate, the pressure difference at each injector is negligable.

Having said that, assuming there may be a temperature gradient along the length of the rail because of airflow, proximity to the radiator, etc., the designers may be trying minimize the effects of fuel temperature variation at each injector.  It's the kind of overthinking a problem that BMW seems to be famous for.

[woodgeek]

I was thinking that temperature gradient could be a factor as well. BMW had insulation on the fuel rail from the factory. I wonder how the lack of fuel rail insulation on a faired K affects their design parameters.

[Laitch]

I’ve never seen a cutaway of one but it would seem to be flow direction agnostic.

Then you should review everything in Vogel's troubleshooting guide. It contains explanations of the K-bike's systems. A cross-section of the regulator is a few pages in from the start.

[The Mighty Gryphon]

Fuel has gotten hot enough on faired bikes to actually boil in the tank.  Even when it doesn't boil it can get hot enough to burn the rider's thighs.  I have installed a fuel cooler on my K75RT which I tour on in the summer to some pretty hot parts of the country.  So far, it has done a good job of keeping fuel temperature within a few degrees of ambient in temperatures above 110F.

Despite the high temperatures encountered by the fuel, in my time on this and other K bike forums, I have not heard of hot fuel significantly degrading the performance of the engine.  It seems to be more of a rider comfort thing.

[woodgeek]

Then you should review everything in Vogel's troubleshooting guide. It contains explanations of the K-bike's systems. A cross-section of the regulator is a few pages in from the start.

Thank you Laitch. I missed that in the guide.

[The Mighty Gryphon]

Fuel has gotten hot enough on faired bikes to actually boil in the tank.  Even when it doesn't boil it can get hot enough to burn the rider's thighs.  I have installed a fuel cooler on my K75RT which I tour on in the summer to some pretty hot parts of the country.  So far, it has done a good job of keeping fuel temperature within a few degrees of ambient in temperatures above 110F.

Despite the high temperatures encountered by the fuel, in my time on this and other K bike forums, I have not heard of hot fuel significantly degrading the performance of the engine.  It seems to be more of a rider comfort thing.

Thinking about this with mornng coffee it occurs to me that even when the fuel is boiling, the pressure of the system is higher than the vapor pressure of the fuel so it can't vaporize in  the rail or the injectors.  Any vaporization that occurs in the intake manifold probably only aids in the dispersation of the fuel in the incoming charge.

[Garthhh]

Thinking about this with mornng coffee it occurs to me that even when the fuel is boiling, the pressure of the system is higher than the vapor pressure of the fuel so it can't vaporize in  the rail or the injectors.  Any vaporization that occurs in the intake manifold probably only aids in the dispersation of the fuel in the incoming charge.

hot fuel is less dense than cold fuel, each squirt of hot fuel has slightly fewer molecules, than cold fuel
the kind of thing that can come into play at the extreme end of performance 

[The Mighty Gryphon]

hot fuel is less dense than cold fuel, each squirt of hot fuel has slightly fewer molecules, than cold fuel
the kind of thing that can come into play at the extreme end of performance

Absolutely, but how many of us will notice a flat spot at 8300rpm on a 100 degree day?

[Laitch]

Absolutely, but how many of us will notice a flat spot at 8300rpm on a 100 degree day?

Everybody who is riding toward Las Vegas in summer.