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Discussion in 'Motorcycle Tech Talk' started by JohnnyBiker, Jul 30, 2010.

  1. JohnnyBiker

    JohnnyBiker Well-Known Member

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    Does the VOES need to be changed when you change the cc of your bike? I know that the VOES is apart of your ignition, so if you have changed the top half, shouldn't you change how much the VOES retards your ignition? Same thing with your time in general??

    Thanks for any input.
    JohnnyBiker, Jul 30, 2010
    #1
  3. hotroadking

    hotroadking Super Moderator Staff Member

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    What is the Vacuum Operated Electrical Switch (VOES)? What does it do and why is it there?

    All Harley Davidson motorcycle carburetor models since the 1984 model year have used the VOES to improve throttle response, increase MPG, and meet EPA requirements for emissions.

    The VOES is a motorcycle part described as a vacuum ignition retard device. That is, under low vacuum conditions the switch is open and has no effect on ignition timing. Under high vacuum, the switch closes and advances ignition timing. Essentially, the VOES is like the vacuum advance in older type automotive distributors.

    The VOES is a normally open vacuum operated switch that closes under 3-5" of vacuum, are adjustable and usually require different settings for different bikes. The switch is connected to a lead from the ignition module. Under high vacuum, 3-5 inches or higher, the switch closes. A lead from the switch to ground closes a circuit in the ignition module. This circuit advances the timing of the spark. The advance increases throttle response and decrease fuel consumption and emissions.

    The vacuum hose is usually connected to a port on the carburetor or intake manifold depending on motorcycle year and carburetor. There are several different VOES switches used the mounting bracket style and operating vacuum being the main differences. The FLHT models have a different vacuum range than the other models. However, just about any VOES can be adapted for use by adjusting the point at which the switch closes.
    As an example...
    FLT: 5.0 - 6.0 inches of mercury
    FXR: 3.5 - 4.5 inches of mercury

    Your vacuum gauge measures in in/Hg (inches of mercury) and/or mm/Hg (millimeters of mercury).

    The point at which the switch closes.

    The switches can be adjusted by removing the potted plug and adjusting the setscrew. You will need an accurate vacuum gauge and vacuum hand pump. We have been able to set the operating point as low as 2 inches and as high as 7 inches.

    Why would you want a VOES?

    We have experimented with converting 1972 and later ignitions from points to electronic ignition. We have used Dyna 'S' conversions for H-D's. We have used Crane, Compufire, Spyke and other Harley Davidson conversion kits. With some of these such as the Dyna 'S', you still have to use the mechanical advance system. This requires service and routine maintenance.

    Others work very well having digital advances and provisions for a VOES switch. We experimented with installing a VOES in a 1983 FX and found we have improved throttle response and better mileage. We also routinely install the VOES in custom built Harley Davidson's and even our own Kenny Boyce framed Harley FXR's use VOES with a Crane HI4 module. During Dyno runs, we found that part throttle roll on power was increased as was throttle response.

    We believe that most street ridden Harley Davidson motorcycles will benefit from a VOES.

    For racing applications or supercharged, turbo-charged or bikes using Nitrous Oxide, we do not recommend using a VOES. This is due to the possibility of a sudden timing change causing a backfire which can be a bad thing under these conditions!
    hotroadking, Aug 1, 2010
    #2
  4. Lucifer

    Lucifer Well-Known Member

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    Lucifer, Aug 1, 2010
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  5. JohnnyBiker

    JohnnyBiker Well-Known Member

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    I have had a good friend also help me with this. My understanding is that if you are under WOT, your VOES will close and advance the timing and will continue to this until your ignition reaches its curve or you begin to level off the throttle. But here is the thing. When I did the engine work, I turned an 883 to a 1200, expecting the new conversion to act just like a stock 1200, that is not the case. I am not positive on this, but I am sure that the 1200 cam and timing is different than that of an 883. Wouldn't you think that you are subjecting your bike to WOT more often with the 10.0:1 CR than that of stock?

    I am starting to think that I have a a lot of issues going on.

    1. My VOES is either not working at all, or since the bike has had a conversion and mild head work done, and also considering that the ignition curves for the 883 and 1200 are different, from the information that I have received, the 883 is 30* and the 1200 is 35*. I am running out of advance.

    2. I am really starting to think that when i did my heads, I was on the right track with doing some mild head work, but I should have gone one more step further and put the 1200 valves in. This was not recommended to do from the person that did my heads. And I cannot think of the reason as to why.

    3. I did not upgrade the ignition. I have looked at the SE ignition, coil, wires, and all of that stuff. The 883 rev limit was 6200 and the SE was 6800.

    What I think that I am going to do is go through and check the VOES to make sure that is operating the way that it should. You know, come to think of it, when I took the carb off to do the jetting, I do not remember seeing the vac hose that is supposed to be hooked to the Carb.
    JohnnyBiker, Aug 1, 2010
    #4
  6. JohnnyBiker

    JohnnyBiker Well-Known Member

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    Then I think that I want to upgrade both the cam and the ignition, if the VOES is working. I have been wanting to upgrade the cam anyways, so I would just put a cam in from a 1200 in. I would also at this time finish with the heads. this time I think that I would put the Buell heads on.

    Of course all of this is dependent on what happens with the VOES.

    Good Plan or bad plan?
    JohnnyBiker, Aug 1, 2010
    #5
  7. JohnnyBiker

    JohnnyBiker Well-Known Member

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    JohnnyBiker, Aug 1, 2010
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  8. ReeseSS

    ReeseSS New Member

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    I wouldn't worry about any timing changes unless you bumped up your compression ratio. The SE ignition modules for 10-1 and over have a small timing retard built in. After market ignition modules can have adjustable timing settings.
    ReeseSS, Aug 3, 2010
    #7
  9. JohnnyBiker

    JohnnyBiker Well-Known Member

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    The bike was kind of half assed done. I am trying to get 1200 performance out of an 883 set up. when I get my back back to shop to correct the compatibility issues, i am going to have that VOSE checked and replaced if needed. After that, I think I will be happy. :D
    JohnnyBiker, Aug 3, 2010
    #8

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