no ignition but spark OK, gas OK

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Waif
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Re: no ignition but spark OK, gas OK

Postby Waif » Fri Sep 21, 2018 9:55 am

Double checked spark plug gap? Valves? Point gap?

Engine Detail: International Harvester C60 gasoline 4-cylinder liquid-cooled 59.5 ci [1.0 L]
Bore/Stroke: 2.625x2.75 inches [67 x 70 mm]
Sparkplug gap: 0.023 inches [0.584 mm]
Intake valve clearance: 0.013 inches [0.330 mm] (cold)
Exhaust valve clearance: 0.013 inches [0.330 mm] (cold)

Point gap per member Bigdog = Mag point gap is .013". Battery ignition point gap is .020".

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CaperKen
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Re: no ignition but spark OK, gas OK

Postby CaperKen » Fri Sep 21, 2018 10:20 am

Thank you, Rick and Jim. Those directions are very clear.

Something else I found in the forum that really cleared up a lot is that even though a Cub has been modified to 12v + external coil, it still must be treated as having a magneto ignition and timed as a magneto.

Can Pertronix electronic ignition be installed on such a system. Will it make any difference?

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Glen
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Re: no ignition but spark OK, gas OK

Postby Glen » Fri Sep 21, 2018 4:30 pm

Hi,
Below are pages from the Cub owner's manual showing the magneto, and the ignition points in it.

http://farmallcub.com/rudi_cub/www.clea ... age-30.jpg

http://farmallcub.com/rudi_cub/www.clea ... age-31.jpg

The rotor in a J 4 magneto is gear driven, the rotor has gear teeth on the lower part of it. Below is a pic of the rotor and it's drive gear.
Remove the cover that holds the rotor in place, and clean out the old grease, and apply new grease to the gears, if it hasn't been done lately.
Align the timing marks shown in the pic below.

If you remove the plate with the rotor in it, don't turn the engine with the plate off, you can lose the timing.

I have read on here that some people say a Pertronix ignition won't fit in a J 4 magneto. I have not tried to put one in a magneto. :)
Attachments
Cub magneto 4.jpg
Cub magneto 4.jpg (25.13 KiB) Viewed 400 times
Last edited by Glen on Sat Sep 22, 2018 3:45 pm, edited 1 time in total.

Gary Dotson
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Re: no ignition but spark OK, gas OK

Postby Gary Dotson » Sat Sep 22, 2018 7:48 am

No, there is no Pertronix kit for the J-4 mag. In order to install one, you would have to switch to the battery ignition unit.

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CaperKen
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Re: no ignition but spark OK, gas OK

Postby CaperKen » Mon Sep 24, 2018 10:20 am

Hi Gary -- When you say "switch to the battery ignition unit" do you mean fully remove the magneto and replace with a full distributor. Because, I have battery ignition (12v, external coil) but the magneto is still mounted with its internal wires disconnected.

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Rick Spivey
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Re: no ignition but spark OK, gas OK

Postby Rick Spivey » Mon Sep 24, 2018 4:30 pm

Just to get you an answer, I'm certain that is what Gary meant. The petronix will fit right into a distributor shell, but not easily into a magneto shell. I love magnetos, but in my opinion, a magneto with external coil is the worst of both worlds. You'd be better off, imo, with either a functioning magneto, or a functioning battery ignition distributor. I personally choose magnetos because then I don't have to keep the 6 volt batteries up in my cubs (I know, lazy). I may someday switch to 12 volt with alternator just so I can keep the electric starter working well, because my wife has taken over mowing the pasture. I want her to be able to start the cub by herself!
Rick Spivey
'52 Cub ("Great Personality") 148xxx
'48 Cub with FH ("Gunny Cub") 38xxx
'57 Lambretta (a slow work in progress)
'74 Triumph TR6 (Mama's toy)

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CaperKen
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Re: no ignition but spark OK, gas OK

Postby CaperKen » Mon Sep 24, 2018 4:44 pm

Rick ... thanks for that confirmation of Gary's statement and further explanation.

I'm determined to get my Cub working as it is currently configured, but you present a strong argument that I'm likely to follow after I'm successful with this task. My Cub worked incredibly well for a 70 year old prior to quitting. I trust the life is still in her ... I just need to find the right key.

Gary Dotson
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Re: no ignition but spark OK, gas OK

Postby Gary Dotson » Tue Sep 25, 2018 8:03 am

Yes, that was what I meant to say. Thanks Rick, for responding for me. There are more reasons than physical constraints that prevent the pertronix from working in a mag, the point cam spinning double speed for one. I'd like to see a kit offered for the J4 but there would be very limited demand.

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CaperKen
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Re: no ignition but spark OK, gas OK

Postby CaperKen » Tue Sep 25, 2018 9:13 am

Very clear. Thanks, Gary.

After I get Rosalie running, I'll have to think about a proper conversion to a distributor.

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Re: no ignition but spark OK, gas OK

Postby Matt Kirsch » Tue Sep 25, 2018 12:08 pm

Thing is, they don't just "jump time" for no reason. Timing is controlled by metal gears that are tightly meshed together. The only way to "jump" would be if you took it apart and physically changed the gear mesh, or if something broke.

Leave the cap off and crank the engine over. Does the rotor turn consistently? If it stops momentarily, you're missing one or more teeth on one or more gears somewhere. Check the feel of the rotor as you turn over the engine slowly by hand. Does the rotor ever "jump" or get real sloppy at any point?

You may be going to that battery distributor sooner than you thought.

Waif
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Re: no ignition but spark OK, gas OK

Postby Waif » Tue Sep 25, 2018 12:17 pm

Rotor might be worth giving a closer look.
It could wear /break before metal gears.
If it can slip ,or has a missing tooth/teeth or slop, that could explain it being off in position.
Though other things could too .like the mag having been removed and it's position changed before reinstalling and no attention to rotor position...
Or a worse condition as Matt stated.

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Glen
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Re: no ignition but spark OK, gas OK

Postby Glen » Tue Sep 25, 2018 6:32 pm

Hi,
If you grease the rotor gears, like I posted above, pull the rotor off and inspect the gear teeth, the teeth can wear, the rotor is not metal. Possible one or more teeth could break, I don't remember seeing a broken one though.
The small gear can wear too.
TM Tractor has new parts. Below is the rotor, and pinion gear. You can see the gear teeth in the pics. :)

http://www.tmtractor.com/new/el/294fp.htm

http://www.tmtractor.com/new/el/615fp.htm

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Rick Spivey
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Re: no ignition but spark OK, gas OK

Postby Rick Spivey » Wed Sep 26, 2018 6:12 am

In my experience the pinion gear (smaller) wears much faster than the rotor. Today's pinions are plastic, rotor is bakelite/brass. If you want to check those parts, the rotor will typically lose whole teeth when it breaks. The pinion will wear in a way that causes the valleys between the gear teeth to get very wide and square, which causes slop, and will ultimately make the timing slightly off or inconsistent. Each of those parts is very expensive, but they need to be correct to make the magneto work correctly.
Rick Spivey
'52 Cub ("Great Personality") 148xxx
'48 Cub with FH ("Gunny Cub") 38xxx
'57 Lambretta (a slow work in progress)
'74 Triumph TR6 (Mama's toy)

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Shane N.
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Re: no ignition but spark OK, gas OK

Postby Shane N. » Wed Sep 26, 2018 6:36 am

I bought a pinion gear and coil from here https://brillman.com/?s=j4+magneto+part ... pe=product for our '47 magneto, it had been converted to an external coil and I put it back original. Been that way for close to 2 years and no problems.
Every home is a school, what are you teaching?

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Rick Spivey
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Re: no ignition but spark OK, gas OK

Postby Rick Spivey » Wed Sep 26, 2018 7:27 pm

I have 3 cubs all running magnetos.They (magnetos) were rebuilt in 2007 (two of them), and the third in probably 2009 or 2010. All have been running perfectly since, and that is the last time they had a good tune-up, meaning the plugs, points, and condenser, etc. are from that same time. I use one of them weekly, 3-4 hours of grass cutting. The other two are used less frequently. This winter they will all get a good tune-up. My point is that magnetos are every bit as reliable as battery ignition, if treated properly. Number 1 thing to keep in mind, never ever snap a magneto without a path for the spark to follow to ground. That will fry a coil every time.
Rick Spivey
'52 Cub ("Great Personality") 148xxx
'48 Cub with FH ("Gunny Cub") 38xxx
'57 Lambretta (a slow work in progress)
'74 Triumph TR6 (Mama's toy)


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