timing

[knuckelhead3865]

I just bought a cub with a j4 mag.....It ran great for about 4 hours. Then it back fired and quit....I found that the rotar bug and drive gear was missing some teeth soooo I figured that was the problem.....I ordered the parts that i needed ... installed them but the tractor still want run..???Have I gotten it out of time..???? If I have how do i fix it ???? There is only one way the drive gear will go on and I didnt notice a timing mark on the bug its self...Please help and thank you.

[Lurker Carl]

http://www.cleancomputes.com/Cub/Cub%20Maintenance%20Manuals/Preventive%20Maintenance%20Manual/index.html

pages 18-22 cover the Cub magneto and timing. There is other information here you'll probably find useful.

[knuckelhead3865]

Thank you for your help...but...the manual did not show me a J4 mag...there are two gears on my bug...one is very small that runs the rotator bug....the other is the bug itself...I am going to try to line the bug up with the number one piston dead center maybe that will do it...if not i start over lol...thanks again

[Rudi]

knucklehead3865:

Unfortunately, there is not a lot of good pics on the J4 Magneto or the Rotor Setup. That is something I have yet to find, but when I do, count on it, it will be on the server.

Follow the directions in the Preventive Maintenance Manual. Pages 18 - 20.

As Carl indicated, this is about the best direction you will be able to get.

There is one other reference that is available on the Cub Manual Server, and that is the GSS-5035 Service Manual Magnetos. It may be of some help to you, although it does not deal specifically with the J4 Magneto.

[WKPoor]

I have never messed with the J4 mag on a Cub, but I think its similar to the H4 on the others models and if so that is literally a piece of cake. Its so easy its almost Murfy proof. First of all, if the rotor is pointed at the right place on the cap when you install it, it will run from any position on the mount. From scratch just put your engine on TDC. Install mag with rotor pointing to #1 on the cap. Now there is a perceedure to time the impulse correctly and rudi's manuals are the place for that. I just want you to know that once you get it on to that point it should fire off fine. I've had my H4 mag off and on countless times and its so easy I don't even worry about being on TDC anymore. I just need to remember where the rotor was pointing at when I last removed it. Once you do get it set up correctly simply mark the mount for the impulse timing and you'll be go to go from then on.

[Jim Becker]

If you haven't removed the magneto, don't. If it was in time it is still in time. You need to install the rotor in the right position. The little gear that drives it will have one tooth with a corner off. The rotor has a rib or seam directly opposite the electrode tip. The rib of the rotor needs to line up with the notched tooth.

This assumes the last person that worked on it didn't get it running through some trial and error method. If they did, you may need to reposition the plug wires in the cap.

[ScottyG]

Read my post on 59" Mowing. This may help a little or at least help to understand some of my trials on timing. Jim is right though, if the magneto was never removed before, it must still be in correct time. Just make sure the marks are lined up properly with your distributor gear and the pinion and that the rotor is set at #1 and that should be it. To be sure, and if you have battery ignition, find top dead center by removing the spark plug from cylinder #1. Put your thumb over the hole and hand crank the engine until you feel an outward pressure. Slighly retard your pulley timing mark a bit. Then, making sure that your kill switch is set to on, unplug your secondary coil wire from the distributor cap and ground it. Slowly hand crank the engine until you see a spark. When this happens, hopefully, your timing mark on the pulley will be right on. If not, you'll have some adjusting to do.

Hope some of this helps.

[knuckelhead3865]

Got it going..lol....Now i'm a proud owner of a 1948 cub yah !!!!!! did anyone notice I spelled Knucklehead wrong ...LOL.... I guess the name fits me huh>>>>

[Rudi]

Knucklehead:

Ifn anyone might have noticed, no one would have said a word... as far as we are all concerned, you can spell it anyway you want to.

Many people cannot pronounce nor spell my name... course these are usually people who can spell names like LeBoutihillier or Manischewisz... so I always tell them I spell it SMITH

[John *.?-!.* cub owner]

With the sign in name I use, do you really think I would question how anyone else spelled theirs?