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Thread: The Cheaty Way to Replace your Early Oilhead Fuel Pressure Regulator, Explained!

  1. #1
    Neglected Bike Adopter
    Join Date
    Jun 2021
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    Middle Tennessee
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    The Cheaty Way to Replace your Early Oilhead Fuel Pressure Regulator, Explained!

    Hey MOA folks,

    After asking a few questions and getting some help, I've finally gotten around to providing at least one technical answer to a question people ask from time to time. The question: "do I really have to remove my transmission and lift the rear subframe to change out my fuel pressure regulator? The book says I have to."

    The somewhat rare failure of early Oilhead fuel pressure regulators CAN, in fact, be fixed without transmission removal or lifting the rear subframe, and I just did it myself yesterday on my 1997 R850R. Before attempting it I couldn't find any actual documentation of the process anywhere despite searching; all I could see was people saying "yes, it's possible," but no instructions or photos or videos as to how.

    I've uploaded a fairly short video to Youtube that hopefully helps anybody who also needs to replace the FPR on their R850 or R1100. While I don't have the resources to film the entire disassembly process, the video does clearly show the aftermath of disassembly where the FPR is accessible.

    Here's the link:
    https://www.youtube.com/watch?v=rIeFMmYrhEE

    Here's a description of the process I used here, in case you don't feel like watching the video. These instructions apply for an R1100 or R850 R, and I believe will be similar for a GS. Other bikes with more fairings will of course require more steps. I do not know whether this applies to R1150 Oilheads as I have never worked on one, but it may be similar.

    Remove the fuel tank, battery, and ABS unit (if equipped). Easier said than done if your bike has an ABS unit, obviously.
    Unhook the throttle cables from both throttle bodies and unhook the choke cable from its lever. Push the choke cable down at the handlebar and pull it at the battery box so that you have a few inches of additional slack in the cable.
    Unscrew the four screws holding the Motronic and its ground wire and mounting brackets to the battery box and let the Motronic rest on the front subframe. Remove the four nuts and washers on the floor of the battery box.
    Lift the battery box and tip it to the left side of the bike; gently lift the retaining clip and slide the Bowden cable linkage unit out from the underside of the battery box.
    Remove the E-clip holding the pivot block in and lift the block out. This will allow you to unhook the main throttle cable as well as the two cables going to the throttle bodies.
    You can then let the battery box rest on the left side of the bike and this should give you access to the fuel distributor, which you can bend slightly upwards by hand to remove and install pressure regulator and its retaining clip. The clip is fairly easy to remove and comes out the right side of the distributor.

    The pressure regulator is also held in by a pair of very tightly-fitting O-rings; to remove it you need to gently rock it back and forth while pulling it towards the handlebars. Be patient and don't flex the distributor too much while doing so and you will eventually get it out.
    Lubricate the O-rings of the new pressure regulator with something safe for the fuel system (Vaseline or silicone oil is a good choice) and use the same careful process to put it back in.

    As always, reassembly is essentially the reverse of these instructions. You will of course need to resynchronize your throttle bodies after this, and bleed your brakes if you had to remove your ABS pump. Make sure you reattach the ground when you screw the Motronic back into its ears on the battery box!

    Note: This only allows replacement of the regulator. It is not possible to replace the fuel distributor this way, as far as I can tell. If yours has a crack or break in any hard nylon parts, you will have to lift the rear subframe to replace it.

    Hope this helps somebody out!
    Owner of the saddest 1997 R850R you ever did see.

  2. #2
    Registered User
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    Apr 2020
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    EAST BAY FL
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    thanks for taking the time to document this procedure.

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