Cub has no spark

Mon Apr 14, 2014 8:53 pm

Hello

Just joined the forum. I've been lurking and reading old posts trying to find some ideas. I have a 49 cub with magneto. It's been barn kept and looks fine but won't start. It is a 6 volt positive ground tractor.

I have replaced the battery and spark plugs. I have put a spark checker on it and there is nothing at all. From what I've read I'm tempted to think it may be the coil? Is there a way to check coil on the tractor? If it's bad, I was thinking about testing it with an external coil before I replace it. Again from what I've read I run the positive from the coil to ground. The negative to a switch, other side of switch to negative of battery? Is there a 6 volt coil commonly available from napa, oreilly or autozone that would not need a resistor? Or are resistors only needed on 12 volt? I have seen c809 at autozone, it's a 6 volt coil. Would this work to test it.

Next question seems a little silly, but I haven't seen the answer around yet. It has the sickle mower. I know where you raise the hydraulics at, but where do you start the pto at? Only thing I've seen that I think might be it is next to the gear lever, a tiny little lever? Is this what starts the pto?

Thanks for all the help. I really want to get the cub running again.

Re: Cub has no spark

Mon Apr 14, 2014 9:27 pm

Don't just start changing parts. May be as simple as filing the points.

That little lever engages pto. Depress clutch, shift the lever, let clutch out and pto should spin. A word of caution. Be careful when lifting the blade part of the sickle mower. The blade can and will slide on its own, so you don't want your fingers in the way. I highly reccomend reading the owners manual for the mower

Re: Cub has no spark

Mon Apr 14, 2014 9:41 pm

Don't just start changing parts. May be as simple as filing the points


:Dito:

I would check the points before I did anything else. If it has been sitting for very long, I would also prime the oil pump.

Re: Cub has no spark

Mon Apr 14, 2014 10:21 pm

Sorry was trying to get my son to bed while trying to post.

I have downloaded the owners manual for cub from a link in an earlier post. I have filed and cleaned points with emery cloth. But I do need to check the gap. Is there a good way to get the rotor to line up with the #1 with an electric start? Or is it just trial until you get it right?

Thanks

Re: Cub has no spark

Tue Apr 15, 2014 5:03 am

Welcome to the forum from Arkansas. On timing a magneto watch this video.
http://www.youtube.com/watch?v=QqucExhxXdE
You can check the coil by temporarily putting on an external coil. Should try to use a point file when filing points to keep from leaving unwanted residue.

Re: Cub has no spark

Tue Apr 15, 2014 8:30 am

Setting the cam on the shaft for points gap is basically trial and error unless you have a hand crank. You might be able to engage the pto shaft and set the transmissin in neutral the use the pto shaft to turn the cam to check the points gap. I''ve never done this but I have used the pto to align the input shaft to the engine/clutch for reconnection after splitting the tractor, so it might work.

Re: Cub has no spark

Tue Apr 15, 2014 9:18 am

If you don't have a hand crank you can remove the spark plugs to remove compression and turn the engine with the fan or by using the pulley on the pto shaft. If no pulley, you can put a pair of vice grips or pipe wrench on the pto shaft to turn it. Just don't forget to remove them before starting (don't ask why I added the last part).

Re: Cub has no spark

Tue Apr 15, 2014 9:23 am

magneto points gap .013

Re: Cub has no spark

Fri Apr 18, 2014 5:31 pm

Well had the day off so I was able to spend a little time with the cub. Checked points gap again and got set to .013. Cleaned a couple of the connections and checked magneto timing. All looked good. I ended up pulling the magneto to take it apart to check everything. I've seen nothing that jumps out as bad. So I'm wondering if I can reassemble and bench test a magneto? If I spin it by hand should I see a spark at the points? Is there a good way to check the coil? It looks fine but I'd like to know if I can check it while it's out?

Thanks for all the help.

Re: Cub has no spark

Fri Apr 18, 2014 6:07 pm

HI 49 cub in ok I have a 49 cub also with a magneto it started running like a deere and then died would not start no spark filed and reset points still noting. removed magneto took cap off of coil it was toast .put new coil in good blue spark.

Re: Cub has no spark

Fri Apr 18, 2014 6:12 pm

So I'm wondering if I can reassemble and bench test a magneto? If I spin it by hand should I see a spark at the points? Is there a good way to check the coil?


Yes, yes, and yes.
be careful to turn the magneto in the proper direction. You should feel a spring that is holding you back, but with enough force it will trip and that is when it should fire.

Re: Cub has no spark

Fri Apr 18, 2014 9:08 pm

Update:

I have a spark now! While the magneto was apart and off tractor I cleaned and checked every connection. Reassembled and set points and retimed it, twice.

I still had the spark checker on it and tried cranking and had spark right away. Then realized I had no gas for the cub so went and got gas and put some in. Nothing. Gas ran out of every orifice in the carb while I was trying to start!

Pulled off the carb and started inspecting. The float was difficult to remove from the bowl there was so much white gunk built up. So the bowl is soaking overnight in carb cleaner and the float is gonna get brushed off in the am. I've cleaned the jet already so I'm hoping with a good carb cleaning it will light off in the morning. A couple times it tried to catch but never would.

Will hopefully reassemble the carb tomorrow and run it.

Thanks to all for the help!

Re: Cub has no spark

Tue Apr 22, 2014 9:40 pm

Well a little disappointed now. Reassembled carb and tried again and still not running. Pulled the plugs and rear two were black and sooty and front two were clean, but all were dry. So, I'm thinking about a carb rebuild kit now. Or would I be better off purchasing a new carb? Or is there a different direction I should be looking?

Thanks again for the help

Re: Cub has no spark

Wed Apr 23, 2014 4:44 am

Since you have spark this may be a little late, but don't "snap" the magneto over without giving the spark somewhere to ground to. That will fry a coil. So next time make sure the internal coil can send the spark to the magneto housing with a piece of spark plug wire. I will assume you static timed the magneto correctly, there are a couple of videos to help with that on this forum.

Now that you have spark, sounds like the carb may be the culprit. Was the idle tube intact when you took the carb apart (long tube screwed into carb top that extends into a reservoir in carb bottom)? Did you open up the two small ports in the carb venturi right above the butterfly plate? Are you sure the orifice in the main jet is clean? Did you reset the idle mixture screw to 1.5 turns out. That screw adjusts air, by the way, so out is leaner, in is richer. There is a carb "how-to" on here somewhere as well. Lastly, did the two carb bodes need straightening at the joint; there is a fixture for this, and information on this forum about how to make one.

Lastly, do NOT buy a carb kit from just anywhere, many are junk. Case IH (expensive) is the best, and Steiner sells a good kit for less money. TSC kits from Tisco are junk.

Re: Cub has no spark

Wed Apr 23, 2014 7:45 pm

Hello and thank you for the replies. The long tube was attached. I did not know about the two ports above the butterfly so I definitely need to check those. The main jet I cleaned out a while back when I first got it so I think it's fine. The idle screw, which one is that? I need to find a diagram of the carb it looks like.

On the ih rebuild kit, is it ftc825? Is this the correct part number?

Thanks again for all the help