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Case Tractors Discussion Forum
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Case SC timing mystery /Jumping timing?

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Walter

06-15-2004 20:52:05




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My SC will not start unless I go thru the timing procedure. #1 tdc time mag till #1 fires. Push the start button and it will start almost instantly and it will run like a top and as long as you want it to. Turn it off and try to restart,,, either after a very short time or a long time and it ain't gunna start... it backfires and pops or does nuthin. Won't even attempt to start,,, retime it and it will start and run again... It started doing this with the old mag and carb so I changed it with a good carb off of a running tractor and put a new mag on it. Same thing. What I can't figure out is why does stopping it mess it up. It doesn't matter if I kill it with the choke or kill it with the mag. If it stops it won't restart unless i retime. New mag is a Fairbanks Morse.

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Bill

06-19-2004 08:00:43




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 Re: Case SC timing mystery /Jumping timing? in reply to Walter, 06-15-2004 20:52:05  
Walter, I stopped over at my farm which I happen to have an extra governer assembly and on this one the whole thing moves at least that much,I think you have a problem with the governer end that its letting the shaft slide too far forward which is then letting the mag drive disengenge from the coupling . Move throttle so the arm on the governer housing is all the way back check the play. If you still have it then you will have to undo the three bolts holding the whole assembly in and see what you have. good luck Bill

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jerry

06-16-2004 10:18:06




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 Re: Case SC timing mystery /Jumping timing? in reply to Walter, 06-15-2004 20:52:05  
Was just wondering if you have to move the mag a lot? Had a tractor that I had to change everytime I went to start it. Then i took off the whole drive assembly and found a half moon key had sheared and that would allow the shaft to turn a little bit at a time.



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todd hamilton

06-16-2004 07:16:57




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 Re: Case SC timing mystery /Jumping timing? in reply to Walter, 06-15-2004 20:52:05  
Interesting problem. The service manual talks about bushing wear on the governor shaft where the mag mounts. I wonder if you have loose bushing there causing the mag to stop out of time when you shut the engine down? Can you confirm how much out of time it is before you loosen the mag flange? Does it fail the same way each time (retarded or advanced)? My SC has a distributor and the mechanical parts in it are pretty loose causing point gap setting to be critical to the open spec. You might try gapping the points at .018 (max open spec) to ensure that they are opening at starting RPM.

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Bill

06-16-2004 06:10:00




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 Re: Case SC timing mystery /Jumping timing? in reply to Walter, 06-15-2004 20:52:05  
Walter, How much are you moving the mag to retime it?? Next time mark the mag and the housing to see if the mag is slowly moving when you shut the tractor off. Good luck Bill



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Walter

06-16-2004 18:12:55




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 Re: Re: Case SC timing mystery /Jumping timing? in reply to Bill, 06-16-2004 06:10:00  
ok guys I got the SC in the shop and pulled the mag. The mag. drive shaft and coupling moves in and out 3/16 to a 1/4 of inch and I think when the tractor kills it slides in to far and causes the mag to jump. While its running the pressure of the gears driving it keeps it pushed out and engaged in the mag. My question is this: How do I take this drive shaft out, I don't see any description or picture of this assembly in my IT manual.

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L.Lamp

06-19-2004 23:20:36




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 Re: Re: Re: Case SC timing mystery /Jumping timing in reply to Walter, 06-16-2004 18:12:55  
Have you had the governor housing out? There is a spring loaded pin in the end of the governor shaft that forces the shaft back to the magneto. The pin, spring or both may have come out without your noticing and without these parts your problem can occur. The pin has about 1/2" of movement against the spring. It is in constant contact with the timing gear cover. Another possibility is that the tractor has been sitting unused for a while and the pin is stuck in not allowing the spring to eliminate the end play. You may have to find another governor with a good spring and pin in it.

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C. Amick

06-17-2004 09:36:13




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 Re: Re: Re: Case SC timing mystery /Jumping timing in reply to Walter, 06-16-2004 18:12:55  
You are talking about taking the shaft out of the magneto right? John Saeli rebuilds them, he should be able to answer your questions. Either post a message for him or [email protected]



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Walter

06-17-2004 11:14:13




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 Re: Re: Re: Re: Case SC timing mystery /Jumping ti in reply to C. Amick, 06-17-2004 09:36:13  
Sorry for the confusion,, no I'm talking about the drive shaft comung out of the governor housing. That's the shaft with the play in it. The one the mag coupling fits into.



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C. Amick

06-17-2004 14:31:31




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 Re: Re: Re: Re: Re: Case SC timing mystery /Jumpin in reply to Walter, 06-17-2004 11:14:13  
So you think the gear to which the magneto and governor are attached slides so that the teeth not longer mesh with the timing gear? Those gears are probably 3/4" thick. I don't see how sliding only 1/4" or so could cause the gears to loose contact? I'm thinking that a gear or something is loose on the shaft and the mag and gear are moving a little independent of each other. Turn the drive gear on the mag and hold the shaft from the other end to see if there is any play. Try turning the engine shaft with something to check for play.

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Allan C

06-17-2004 15:41:26




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 Re: Re: Re: Re: Re: Re: Case SC timing mystery /Ju in reply to C. Amick, 06-17-2004 14:31:31  
i Think he means the mag coupling is jumping. Yes, you will have to fix the endplay.



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Walter

06-17-2004 17:21:29




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 Re: Re: Re: Re: Re: Re: Re: Case SC timing mystery in reply to Allan C, 06-17-2004 15:41:26  
Yes I do mean the mag coupling is jumping. In fact when the shaft is pushed all the way in,, the distance from the magneto mounting flange to the face of the coupling is greater than the depth of the ears on the mag. The drive gears are helical( I think thats the right term) so when the engine is running it forces the shaft outward and engages the mag ,,, when it stops if the engine rotates slightly backward the opposite occurs ,, sucking the shaft inward and disengaging the mag from the drive coupling. How do I get the mag drive coupling off the shaft? Thanks everybody.

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C. Amick

06-18-2004 05:22:49




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 Re: Re: Re: Re: Re: Re: Re: Re: Case SC timing mys in reply to Walter, 06-17-2004 17:21:29  
Can you build up the male side of the coupling (the rib) with some J.B. Weld or brass?



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Jerry (WI)

06-17-2004 18:13:34




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 Re: Re: Re: Re: Re: Re: Re: Re: Case SC timing mys in reply to Walter, 06-17-2004 17:21:29  
I have seen mags with short drive lugs and I have seen mags with a longer reach on the drive lugs. Could you use the longer reach for now? Your shaft on the tractor might be as simple as a snap ring or something that wore out. Good luck, Jerry



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