Old Kohler doesn't want to start

Discussion in 'Mechanic and Repair' started by Gratefulgary, Oct 4, 2007.

  1. Gratefulgary

    Gratefulgary LawnSite Member
    from z6 NY
    Messages: 4

    The patient is an early 70's Jacobsen GT 1200 with a Kohler cast iron line, automatic compression release (ACR), Model K301AQS, spec 47606D, ser. # 8015920.

    The symptoms are that if I get it running it pops frequently and will stall if I try to change the throttle setting. Sometimes it will respond ok if I change the throttle very slowly. The popping has existed for at least a year, increasing in frequency with time, now occurring every couple of seconds. While trying to start it, some drops of either dirty or oil contaminated gas will spit out the carb. Other than the popping, it has started and run fine until the day it wouldn't. The air cleaner housing had enough fluid in it to suggest the carb-spitting may have been present for a while. The spark plug is very fouled with dry carbon deposits. The points were also shot, with a nice sized contact circle appearing evenly pitted on both contacts.

    I replaced the plug, points, condenser, fuel and air filters. I had previously adjusted the high and low settings on the carb according to the owner's manual. The new plug begins to foul with carbon deposits immediately.

    It uses about a half a quart of oil over the course of the season, about 50 hrs. and doesn't smoke, much.

    It is getting spark. I will admit, however, that I am not a good judge of what constitutes "good" spark. I will further admit, that being a "what the heck" kind of guy that I have been using automotive coils for years and that includes the current coil. It is getting better spark than last year when it wouldn't start and there was a weak yellow spark. The current spark is reasonably blue and makes an audible yet subtle ticking sound.

    I took off the carb and breather cover and observed the action of the valves to see if I could discern any problems with the intake. I could not. Looking in the intake manifold I could see the deposit line on the stem that doesn't go into the guide and it does not appear, at least based on that observation that the valve is sticking. Although I suppose that it could take a bit of debris smaller than that to perhaps cause a problem.

    I did a compression test, for what that's worth with ACR, and it develops about 32 psi.

    Before I yank the head and/or buy any more parts, can anyone head me, well, somewhere? If I do pull the head, what do I torque the heads to when I re-assemble?

  2. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    Is this actually carbon deposits or black soot ?

    I have never seen carbon build up this fast on a plug, If it is black soot I would say the carb is running way too rich. The adjustments in the owner's manual are only a starting point to get the engine running then they must be fine tuned to each engine.

    32lbs compression sounds way low for this engine even with the ACR, It should be at-least 50/60 to start and run, It wouldn't be a bad idea to pull the head and de-carbon the head/piston and valves. You may find a piece of carbon broke loose and got stuck under the intake valve, I would also recommend checking the valve clearance.

    You should be able to enter all your engine info below and down-load a PDF service manual with all the specs and procedures you need.

  3. pugs

    pugs LawnSite Gold Member
    Messages: 3,025

    I have allways heard from my dad that using a regular automotive coil on the K series is a bad idea. He doesnt know why, but if you use one it will work for a while but not last anywhere near as long as the proper Kohler coil.

    I dont think it will cause any running problems, just not work for very long. Just a FYI.
  4. topsites

    topsites LawnSite Fanatic
    Messages: 21,653

    Shoot, shut down the fuel then pull the carburetor bowl off and spray all of that out real good with some carb cleaner and compressed air, re-assemble after the carb and float mechanism is good and clean and working, open the fuel back up.
  5. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    While that may help (for a rich run/flooding situation) along with checking the float for a pin hole (fuel inside) and replacing the float needle valve. That will have no effect on the 32lbs compression or popping back out of the valves......
  6. leeker

    leeker LawnSite Member
    Messages: 51

    just something to look at before you go to far. check the trottle shaft to see what it is like. see if it is loose or very loose as most are. MAKE SURE ALL THE SCREWS ARE IN THE SHAFT/BUTTERFLY AND NOT ON THE FACE OF A VALVE (LOW COMPRESSION). the carb alone will scare you $$$$$$. i had one of these that would run like you stated, but had a sharp tapping noise. turned out the cam was cracked, but the cam is slid over a shaft and this held the cam together letting it run, but rough. this could also cause low compression.
  7. Gratefulgary

    Gratefulgary LawnSite Member
    from z6 NY
    Messages: 4

    Thanks you guys. I knew that about the auto coils, but what the heck. I get them for free (used) or just a couple of $$. I have downloaded the service manual from the Kohler Classic engines site. I will clean and rebuild the carb and critically check the points adjustment. I had the float off and it doesn't have any fuel in it. If none of those fix the problem.....off with it's head!

    Rob, you're right, its soot. Although, of course soot is carbon, I understand using correct context can make all the difference. I'll be more careful in the future. As my old graduate school advisor used to say "Don't say tin foil if what you mean is aluminum foil."

    Thanks again,

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