85 K100 throttle. What is this hose for?

[oldnslow]

This hose runs from the rear throtttle body to the under side of the fuel pressure regulator. What is its purpose? It looks slightly deteriorated. Is it a vaccuum hose? It also has a heat shield type wrap on it.

Thanks.

[DIL]

It goes to the fuel pressure regulator, the bottom nipple. Replace if it's kaput. The flexible plastic hose cover will likely be very stiff. You can weasel a hand in there with the top of the air box off from the right side of the bike.

[oldnslow]

I can easily replace it...I have the airbox and all the tupperware off of the bike now. is it a fuel line of some sorts or a vacuum hose? What about the cover? Is it important to keep it intact?

[DIL]

I *believe* it's a vacuum hose. Just pull it off the nipple. I reused mine as it was in good condition, but trimmed off the ends of the plastic coating - once it's off, it will not want to go back on. I am not sure if the hose from the dealer comes with the coating. It's a pricey little bugger, regardless.

You'll want to use some KY or silicone grease to make it easier to slide the coating back on. The only place I would ever see an issue with the coating NOT being on the tube is right at the first bend coming from the regulator, where the hose likes to come in contact with the engine block.

As long as you are in there, check/replace the hose from the TB to the vacuum switch (on the opposite end of the TB) - it likes to wear as well.

[98lee]

It's a vacuum hose. Not sure about the '85 but the newer bikes have a coiled wire covering (like a spring) wrapping the hose to keep it from kinking.

[PGlaves]

It is a vacuum line to the fuel pressure regulator. It needs to be connected, and in good condition (not leaking).