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Thread: 95 RT Crankcase vent Needed?

  1. #1
    ABE456
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    95 RT Crankcase vent Needed?

    I noticed the former owner plugged the crankcase vacuum tube - well I think that's what it is. It is located next to the starter. Looks like it used to run back to the air box through some fittings and a small tube of some sort.

    I also noticed a wee bit of oily/carbon/ dust near the front cover vents, down at the bottom. At first I thought it was coming from the crossover pipe clamps, but now I'm not so sure. The bike runs well, doesnt use oil, and compression is within spec.

    Shouldnt that crankcase vent be hooked up and run back to the airbox? All the other EPA stuff has been removed.

  2. #2
    Administrator 20774's Avatar
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    You really need some kind of system to allow the pressurized air inside the case to equalize when the pistons are moving in towards the crank. That's the purpose of the vent or breather valve. If not allowed to breathe, the danger is that various seals, such as the rear main seal will let loose to relieve the pressure. Any other weak points in the oil sealing system might also be stressed.

    Some due run the oil mist/vapor out to collection bottle somewhere. But I think BMW designed a reasonable system to deal with it. Why not return it too stock?
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  3. #3
    Rally Rat
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    Crankcase Vent

    The vent you've found was to vent the fuel tank, via a solenoid controlled valve, into the crankcase. Put a vacum nipple cap from a "K" on it with some silicone sealer and let it dry before starting the engine.

    Your crankcase is vented by a reed valve under the rectangular cover at the top rear of the engine.

  4. #4
    ABE456
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    Quote Originally Posted by lostboy View Post
    The vent you've found was to vent the fuel tank, via a solenoid controlled valve, into the crankcase. Put a vacum nipple cap from a "K" on it with some silicone sealer and let it dry before starting the engine.

    Your crankcase is vented by a reed valve under the rectangular cover at the top rear of the engine.


    Thanks for clearing that up. Will do.

  5. #5
    --Tony AnnapolisAirhead's Avatar
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    Quote Originally Posted by abe456 View Post
    I also noticed a wee bit of oily/carbon/ dust near the front cover vents, down at the bottom. At first I thought it was coming from the crossover pipe clamps, but now I'm not so sure. The bike runs well, doesnt use oil, and compression is within spec.
    If its the front cover to the engine you are referring to (covers the diode, alt and distributor/bean can), I have the same thing. It's mostly road dirt and brake dust in my case.

    Note: If you decide to remove the front cover to clean it, disconnect the negative lead from the battery first or risk shorting out the diode board.

    I removed my emissions gear with a kit sold at Bob's BMW for about 10-12 bucks I think. It came with all the necessary plugs. Most dealers probably carry them.
    Last edited by AnnapolisAirhead; 10-06-2008 at 07:43 PM.
    '83 R100RT'd
    '71 R75/5 SWB
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