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Followup To
Question -
Hi. I read your recent response concerning this same question. I am helping an older gentleman with his JD 400. The enine surges typically at WOT until it warms up then eventually smooths out. I have replaced points, condenser, plugs, hi tension leads and set timing to no avial. We then removed carb and rebuilt and also replaced throttle shaft. Same symptoms occur, surges until warm up. I then removed gov. linkage to carb, and moved carb throttle manually. No surging at all, but I did notice gov. linkage kicking back and forth while I held the throttle at a steady speed. With gov linkage disconnected and me moving throttle shaft, engine runs very smooth. For tune up specs. we used the JD service manual applicable to this engine. The JD manual in trouble shooting suggests surging could be to a faulty govenor,along with other trouble shooting suggestions which we accomplished. Thank you very much and looking forward to you response. Mark D.
Answer -
Have you replaced the governor spring and checked the engine RPM. The internal part of the governor rarely fails...if it does the engine will run very, very fast and you will have no throttle control.
Normally on these older engines I'd recommend checking the throttle shaft but you've replaced it. Was the old one pretty wore? I usually find them in bad shape.
Back the governor spring. An old spring will sometimes loose tension; this it rare but it can happen. Also, some engines are more sensitive to governor spring tension...the more sensitive it is is usually better except if it constantly surges.
Also, check the engine mounting bolts. Loose bolts cause more vibration which could be vibrating the governor spring. One book I read said you could take a pencil eraser, the kind on a wooden pencil, hold the eraser end on the spring to see if it smooths out the engine. This supposedly checks for vibration and weak springs. Don't know for sure if it works but you might give it a try.
Does the manual tell you the engine RPM?
Let me know.
Eric
Eric. Thank you for the quick response. The throttle shaft had minimal wear,possibly 5 to ten thousands of wear or wobbling within it's bore. I did try moving the governor spring to different hole on the gov. arm as suggested in the JD manual, operation remained the same. I did notice that the hole in which the spring resided in the original location was elongated ie, not round. The spring also felt very strong, hard to stretch when I moved it to a new hole. Top speed rpm is 3600 and to set timing with timing light book suggests 1700 rpm. again when I remove linkage and work throttle manually engine does not surge. Maybe I should go ahead and replace the gov spring. I emailed the same question, problem to Kohler, wonder if I will get a response. Mark D. 816 537 7893
AnswerPlease let me know what Kohler says. Older engines are much more difficult to rpair because there may be several small items that add up to the problem.
As for moving the spring, I know on some gensets and welders that the spring hole location can make a big difference on engine performance. For these applications we always refer to the specific engine code and serial number to set the engine RPM and governor.
Let me know what you find.
Eric
