adsm08 2,788 #1 Posted July 22, 2019 So last week I mowed, it ran great, no problems. Went away for a week, came home to long grass, went to mow, runs rough, stumbles, black smoke, shoots flames out the muffler. Lovely, timing is wonky. I got out the manual, took off the belt cover, timing plug, turned and turned and turned, scraped some, found and painted the S, put the timing light on it and my paint mark isn't even in the window when the light flashes. So I turned some more to make sure I had the right S and I can only find the one, so it must be the right one. With the S centered in the window the plunger isn't even touching the points. That seems wrong to me, since the coil should fire when the points open, not while they are closed. Is this right, or is it possible the cam has slipped some? Share this post Link to post Share on other sites
rmaynard 15,964 #2 Posted July 22, 2019 Are you turning the flywheel in the correct direction? There is only one "S" mark. The other is top dead center. I've seen a cam shaft break, but never slip. 2 Share this post Link to post Share on other sites
953 nut 58,419 #3 Posted July 22, 2019 If your ignition points are not corroded and have not been moved I doubt that the timing suddenly went wrong. Your flywheel makes two rotations for each power stroke of the engine. The points only open slightly ahead of TDC on the power stroke. If your engine has a compression release cam shaft the timing light will give an accurate low RPM reading, but if it has the spark retard cam the timing light will only be accurate while running. Share this post Link to post Share on other sites
adsm08 2,788 #4 Posted July 22, 2019 26 minutes ago, rmaynard said: Are you turning the flywheel in the correct direction? There is only one "S" mark. The other is top dead center. I've seen a cam shaft break, but never slip. 18 minutes ago, 953 nut said: If your ignition points are not corroded and have not been moved I doubt that the timing suddenly went wrong. Your flywheel makes two rotations for each power stroke of the engine. The points only open slightly ahead of TDC on the power stroke. If your engine has a compression release cam shaft the timing light will give an accurate low RPM reading, but if it has the spark retard cam the timing light will only be accurate while running. I checked it while running so I really really hope the engine was spinning in the right direction. It started pouring here while I was typing the original post, so I will go spin it another rotation once things clear a bit. Share this post Link to post Share on other sites
stevasaurus 23,117 #5 Posted July 22, 2019 Check your gap...the points control the timing. Should be .020 gap...some run better at .018 gap. You also may have bounced some crud around in the fuel tank or carb. May have something clogging up the works. 2 Share this post Link to post Share on other sites
rmaynard 15,964 #6 Posted July 22, 2019 21 minutes ago, adsm08 said: I checked it while running so I really really hope the engine was spinning in the right direction. Okay. I thought you were using the static timing method with a meter or light. Share this post Link to post Share on other sites
richmondred01 2,292 #7 Posted July 23, 2019 (edited) Cams break they don’t slip. Check your point gap. Replace if required with Kohler points. As already stated the timing is set by the points. Also, the timing may be off if the flywheel key has sheered. Edited July 23, 2019 by richmondred01 Share this post Link to post Share on other sites
adsm08 2,788 #8 Posted July 23, 2019 46 minutes ago, richmondred01 said: Also, the timing may be off if the flywheel key has sheered. Now this is starting to move in the direction my gut is taking me. Years ago my truck sheered the roll pin that holds the drive gear to the distributor shaft, and sometimes it would run great, sometimes it wouldn't even start, but the timing seemed to changed at random, which is what the tractor is doing now. Share this post Link to post Share on other sites
troutbum70 857 #9 Posted July 23, 2019 What would cause a cam to brake outside of flawed material or poor machining? Share this post Link to post Share on other sites
pfrederi 18,406 #10 Posted July 23, 2019 If the engine ran well previously and there was no traumatic stop I doubt the flywheel key would shear. Briggs and Techy used soft flywheel keys especially in rotary mowers that would shear when the blade struck something hard.. your Kohler has a steel key and unless your deck belts were really tight and you hit something really solid...no shear Share this post Link to post Share on other sites
rmaynard 15,964 #11 Posted July 23, 2019 12 hours ago, troutbum63 said: What would cause a cam to brake outside of flawed material or poor machining? The only cam that I ever saw break was in a K-91 engine that broke a connecting rod. Before the rod came through the side of the crankcase, it must have hit the cam gear/shaft and cracked it where the shaft and gear meet. The owner of the engine told me that after the crankcase was welded and the rod replaced, it didn't take but less than an hour for the camshaft to separate from the gear. There was a clunking noise, and the engine stopped dead. Share this post Link to post Share on other sites
adsm08 2,788 #12 Posted July 23, 2019 I am starting to think the condenser is the issue. The crank key is OK, I set the timing statically and it runs a bit better, but still rough. The crank key is OK, It still seems like the points open too late though. S on the mark for the timing window. Points actually open. Share this post Link to post Share on other sites
Burnerman 759 #13 Posted August 9, 2019 Could it be possible the plunger is worn down? Share this post Link to post Share on other sites
