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  1. #1
    Gold Member
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    Jan 2012
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    Kubota L2500, Oliver Super55

    Default Gas engine throttle lag governor or fuel delivery??

    Got an issue with my old oliver super 55 that hopefully some of you guys that work on old iron can help give some ideas on what it might be.

    When I increase the throttle there is an excessive amount of travel without the engine rpms increasing and then once hit a point it will increase significantly such as idle being at about 800 rpm and travel throttle about 1/2 distance with no engine rpm increase and then will jump up to 1600 rpm. Increase a little further and in might drop down to 1200-1300. Put it at W.O.T and it will hold at about 2500 rpm.

    At first I thought it was fuel delivery or hanging float but tore apart the carb and the float and needle valve are traveling properly. Disconnected supply line and seems to be supplying adequate fuel.

    While under load the tractor sounds like the governor is operating appropriately for load/draft control. It's definitely working on rev limiting.

    Throttle linkage doesn't appear to be hanging up but I will probably go through it once again to be sure.

    Looking for some other ideas that might cause the erratic throttle control??

  2. #2
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    MASSEY, CASE , FARMALL

    Default

    Is there a spring in the throtel linkage? It can be streched and is not ajusting the govenor when the throttel is pulled just taking up the slack.

  3. #3
    Gold Member
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    Kubota L2500, Oliver Super55

    Default Re: Gas engine throttle lag governor or fuel delivery??

    yeah there is a spring on it and there is a little play in it from what I can remember. (I wish I was where the tractor is so I could add a pic but such is not the case) My guess is it's the original OEM spring. I know it has a zenith carb similar to ford "N"s and a centrifugal governor.

    If I disconnect all the linkage and then just rev the engine by manipulating the armature directly on the cam with all the throttle/governor linkage disconnected this should give me an idea I would think?

    I had an old jeep that had a two barrel carter carb on it originally and that thing was notorious for having a dead spot in the carb. I ended up replacing the carb on it. Are these old zenith carbs known for the same thing? The tractor still runs well its just kind of a pain manipulating the throttle to keep the RPMs up when under load.

  4. #4
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    MASSEY, CASE , FARMALL

    Default Re: Gas engine throttle lag governor or fuel delivery??

    Quote Originally Posted by super55 View Post
    If I disconnect all the linkage and then just rev the engine by manipulating the armature directly on the cam with all the throttle/governor linkage disconnected this should give me an idea I would think?
    Ya. That should work. It will help you isolate the problem. I am also thinking that the linkage could be loose. There isn't much on these old tractors so it shouldn't be hard to find the issue. Where in northern Michigan are you. I am across the border from the Soo.

  5. #5
    Gold Member
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    Kubota L2500, Oliver Super55

    Default Re: Gas engine throttle lag governor or fuel delivery??

    Quote Originally Posted by MIKE R View Post
    Where in northern Michigan are you. I am across the border from the Soo.
    I'm over in Traverse City in the pinky of the mitten. Haven't been up to the Soo in a couple of years but had a good time last I was there. I figured if I did this and it corrected the problem at least I have it narrowed down to two causes. If it doesn't fix it than I don't know. Maybe start looking for a vacuum leak in the intake manifold perhaps. Will probably throw a new set of points and plugs in it just because it is such cheap maintenance and I've only had the tractor for a little over a year. I have no idea when they were last changed but the tractor has always ran so smoothly I never considered changing them. Not sure if bad points/plugs would cause lag/dead spots in parts of throttle travel anyways.

  6. #6
    Epic Contributor Soundguy's Avatar
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    Central florida
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    ym1700, NH7610S, Ford 8N, 2N, NAA, 660, 850 x2, 541, 950, 941D, 951, 2000, 3000, 4000, 4600, 5000, 740, IH 'C' 'H', CUB, John Deere 'B', allis 'G', case VAC

    Default Re: Gas engine throttle lag governor or fuel delivery??

    preload or slack in a gov spring COULD do it.

    excessively lean mainjet setting can cause some lag too.

    if choke helps.. check carb.. otherwise visually inspect linkage..

  7. #7
    Gold Member
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    Kubota L2500, Oliver Super55

    Default Re: Gas engine throttle lag governor or fuel delivery??

    Just wanted to give an update on this and let everyone know it was fixed. It ended up being linkage as others had suggested it was actually a metal arm connected to a return spring that had rounded out and had play in it and it was causing the linkage to snag when either trottled up or when the governor kicked in. Saved a little metal off the arm and bored out and put a new bolt in it and now it works as good as the day it left the assembly line.

  8. #8
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    Default

    Good to hear.

  9. #9
    Epic Contributor Soundguy's Avatar
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    ym1700, NH7610S, Ford 8N, 2N, NAA, 660, 850 x2, 541, 950, 941D, 951, 2000, 3000, 4000, 4600, 5000, 740, IH 'C' 'H', CUB, John Deere 'B', allis 'G', case VAC

    Default Re: Gas engine throttle lag governor or fuel delivery??

    glad to hear ya got it.

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