85K100RS vacuum line question - K-Bikes.com - Excellence in Motion
 
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post #1 of 10 (permalink) Old Feb 11th, 2013, 1:14 pm Thread Starter
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85K100RS vacuum line question



Here is a photo of the end of the vacuum line that runs from the bottom of the fuel pressure regulator. My questions are:1. Do I need to encllose the replacement line in some kind of sheath as in the photo or is naked line ok? And 2. if a sheath is recommended, what should I use?

Thanks.
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post #2 of 10 (permalink) Old Feb 11th, 2013, 3:08 pm
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Part 13541461531 - about $3, It's actually a metal spring that goes around the vacuum line. It keepsthe vacuum line from making direct contact with the engine block.
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post #3 of 10 (permalink) Old Feb 11th, 2013, 5:20 pm Thread Starter
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Insulation

Quote:
Originally Posted by FlyingDuck
Part 13541461531 - about $3, It's actually a metal spring that goes around the vacuum line. It keeps the vacuum line from making direct contact with the engine block.
Plus $8 for shipping or $7 in gas.

So, it is acting as a heat insulator to reduce the amount of heat transferred to the line? What is the reason for it?...extending line life?...reducing the effect the heating of the line has on fuel pressure regulation?

If it is the former, I wont worry about it. But if it has an effect on how the mc runs, then I will need to buy the sheath or find a substitute. Maybe I can wrap the hose with muffler tape or some other insulator.

Thanks for the info.
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post #4 of 10 (permalink) Old Feb 11th, 2013, 5:59 pm
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This spring also have a second purpose, it won't be any kinks at the vacum hose that easily when the spring is present.

Inge K.
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post #5 of 10 (permalink) Old Feb 11th, 2013, 9:21 pm Thread Starter
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I need the spring

Quote:
Originally Posted by IngeK
This spring also have a second purpose, it won't be any kinks at the vacum hose that easily when the spring is present.

Inge K.
Im thinking now that is its primary purpose, to prevent the vacuum from collapsing the line at the places where the line curves around. I bought some line locally, but its OD is larger than the ID of the sheath that was on. I need to order a part for the Tiger, so I think I will buy the line and the sheath for the K at the same time.

Thanks for the info.
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post #6 of 10 (permalink) Old Feb 12th, 2013, 10:48 am
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Right or wrong. I've always assumed that it was there to keep the rubber of the vacuum hose from chafing on the engine block and wearing through. Since vacuum line is designed to be subjected to vacuum you'd need quite a bit a vacuum to actually collapse it. The front vacuum line on the 85 TBs is subjected to the same vacuum and has nothing around it.

Last edited by FlyingDuck; Feb 12th, 2013 at 10:53 am.
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post #7 of 10 (permalink) Old Feb 13th, 2013, 4:01 pm Thread Starter
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Quote:
Originally Posted by FlyingDuck
Right or wrong. I've always assumed that it was there to keep the rubber of the vacuum hose from chafing on the engine block and wearing through. Since vacuum line is designed to be subjected to vacuum you'd need quite a bit a vacuum to actually collapse it. The front vacuum line on the 85 TBs is subjected to the same vacuum and has nothing around it.
You very well might be right. I know my front line doesnt have the spring sheath. I need to look at the schematics to see if that is OEM. If so, then the issue is what the difference is between the two so that one requires the sheath and the other doesnt. The only three things I can think of are 1. Preventing chafing, 2. Insulating from heat and 3. Preventing kinking/ collapse. I would think the only relevant difference would be routing. So, what are the routing differences?...Number of curves, severity of curves, proximity to heat source and likelihood of damage caused by rubbing against objects the lines touch? Anything else you can think of?

So, what is the difference in the routing of the two lines?

Does the front line make any sharp (~90 degrees) turns as does the rear? Does the front touch line touch anything other the two ports?

I need to work on the fast idle. I will take a closer look at the front line routing when I do to see if anything obvious jumps out. Until then, if forced to bet, I will go with kinking. But I am not betting large.
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post #8 of 10 (permalink) Old Feb 14th, 2013, 4:36 pm Thread Starter
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ooops!

Quote:
Originally Posted by 97tiger885
I know my front line doesnt have the spring sheath...



So much for that thought. Looking closer I see that my front vacuum line does have the springed sleeve. I know the mc ran fine with the sleeves and BMW must have had a reason for putting the sleeves on; so, I am going to pay the money to get stock sized line and keep the sleeves.
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post #9 of 10 (permalink) Old Feb 16th, 2013, 4:40 pm
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BMW charges $21 for that vacuum hose.

And the price is probably for a meter of it - about four times as much as you need.

You can by a foot of it (more than you need) for <$1 at any auto parts store.

Here's a set of K100 TBs I just refurb'd with generic vacuum hose. I can guarantee you that the air won't know the difference between that and a BMW product.


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post #10 of 10 (permalink) Old Feb 16th, 2013, 8:12 pm Thread Starter
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Quote:
Originally Posted by FlyingDuck
BMW charges $21 for that vacuum hose.

And the price is probably for a meter of it - about four times as much as you need.

You can by a foot of it (more than you need) for <$1 at any auto parts store.
I know it's craziness. If there is a next time, I will do it your way.
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