1954 Cat 112 Bosch MJK 4/2 360C-17 Serial no 3A 280424 I'm having a problem diagnosing a no spark issue with the pony motor magneto. The points look good, the rotor looks good, The cap looks good, the condenser I replaced. Questions I have. 1. What does the points gap needs to be set? 2. Can the coil come and go, work and then stop working? 3. How can I test the magneto coil and what ohms should it read? 4. When I spin over with a drill should the points make a blue spark? 5. I noticed an M on the gear does that have to match up to any marks when reinstalling? What I've done. Cleaned points. Replaced condenser. Inspected coil and cleaned all contact point shiny. Made sure no wires were grounded out. Tried different spark plug wires Thanks, Damon
Ground the spark plug to the magneto, only use copper core ignition wire, test mag with both spark plugs connected, turn mag by hand should feel a hard spot while turning the gear in the correct direction ( arrow stamped on housing) you don’t have to turn it fast to get a spark. Also you can check for spark with the cap off, should have a nice spark at the points while turning over by hand.point gap is 020. The M mark on the gear is for timing the mag to the starting engine. If there is no resistance while turning the gear, your mag needs to be remagnetized, coil could be also. Best to have a magneto shop look at it. There are YouTube videos on how to time magneto to the engine. D2,4 use the same starting engine as your 112. You also could join the acmoc caterpillar club, they have a great library you can access. You can try eBay for service manual for a Cat D315.probably missed something,it’s been over 15 yrs since I worked on them,& sold all my manuals, ,good luck
Thank you, for this good information. I never noticed that little arrow on top of magneto and that you could twist over only by hand and still get a spark. I did as you said with both spark plugs grounded to magneto housing and twisted by hand and I got nice blue spark. I'm not sure why it started working I didn't really do anything but what you told me. The gap is at 15 when you said 20 but that's the only one I had on me. I think I have something off, the timing or the carburetor sat up for too long because alI I'm getting is popping no start. I do have a no. 112 motor grader gasoline starting parts catalog but no real instructions and nothing online that I could find. I'm not sure exactly how to time the magneto to the pony motor. I see there is a square inspection bold you take to see if it's aligned right but aligned to what, I seen no marks on the pony motor gear. The guy who sold it to me 10 years ago or so, when we took out magneto we put two dimples on each ajusted tooth on the pony motor and one dimple on the magneto tooth, that tooth slid between the two teeth we but diples on so I thought but that was years ago, It's all fuzzy now. I'm not sure of the correct way to time or what side has number one cylinder or where is the other timing mark is. That M on the magneto lands right on a tooth and not between them so I was looking for a mark between two teeth on the pony motor that I never did find. I don't think there are any timing marks on the pony motor gear that I could see. I'm not even sure why the M is on the magneto gear because I find it hard to believe you could see it through the inspection hole because of the M location. It would be great if you knew exactly how to do this magneto to pony motor timing or point me to a good video or diagram that was easy to follow the directions. If I knew the timing was right on, that would only leave me fauled up plugs or leaky plug wires or carburetor. Thank you for the help you have already given me it was actually really helpful to know those little things. That put me on a good position knowing that it should throw a spark by hand and a drill wasn't needed. I was surprised it threw a nice blue spark with a simple twist of the hand. Thank you,
Hi Damon, Thank you, Just do a google search, I typed , How to time a magneto on a D4 caterpillar, got lots of information. YouTube is also great. Ken
Thank you. I managed to get it timed pretty good because it started on first start, diesel engine started right up too. When I bought this grader it had a weak clutch and that's all the way adjusted out. One day I was grading my farm road and I lost all clutch. I could smell the clutch so i thought this is about to go and it did. Then for whatever reason it grabbed clutch again and off it went for about 5 minutes and then I lost all clutch and there was just enough grab I backed it up and left it parked there for the last two years. I decided to get it back up and running because it had been sitting so long so I posted some questions and got answers and now it's running. But to my surprise I put it in gear and off it went, I started grading the farm road and after about 45 minutes I lost the clutch again. I have no ideal why it worked now I'm thinking maybe the clutch is getting fluid on it some how. I'm not sure why I smelled the clutch burning before but I know what a burning clutch smells like. The pony motors front seal leaks a quart of oil, not kidding every time I start it but that's never caused me any problems in the past. Can somebody tell me what they think might be going on? Thank you.
Starting engines are known for this problem, the main brgs are made of aluminum, when they are worn badly they take out the oil seal plus that’s a heavy flywheel. You probably also have lots of endplay . Squatch253 has excellent YouTube videos on these.
Thanks for your help. I'm not too worried about the pony motor front seal leaking oil as long as it starts I'm okay. My big issue right now is that the clutch is slipping. It slips (won't move) then after it sits for a year it moves and works great.
Thanks for your help. I'm not too worried about the pony motor front seal leaking oil as long as it starts I'm okay. My big issue right now is that the clutch is slipping. It slips (won't move) then after it sits for a year it moves and works great.