No spark at plugs

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JFB
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No spark at plugs

Postby JFB » Thu Jun 04, 2015 6:00 pm

Hello everyone, I just recently bought my first cub a 1949 model and I am trying to get timing set on it . I removed the mag and set it at TDC #1 piston , the governor was out of time. I removed governor and set the timing marks and the slots line up with the mark on the housing . Then I changed points, condenser, plugs, plug wires and distributor cab. I didn't replace the rotor because i couldn't get one in my area. So i put it all together lined the marks up on the rotor and the mag pinion gear and got it all together cranked the engine and it ran for about a minute and died. I have no spark at the plugs but I can put a plug wire on the coil and I have a great blue spark. It was running before I changed everything with the old rotor but not with the new cap . Any help would be appreciated

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Re: No spark at plugs

Postby Bigdog » Thu Jun 04, 2015 7:36 pm

Pull the distributor cap and see if the rotor is still turning. It may have stripped either the rotor or pinion gear teeth.
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Re: No spark at plugs

Postby tst » Thu Jun 04, 2015 7:49 pm

check the coil if everything is turning as it should like Bigdog mentioned, they go bad on those old mags after many years, its only 65 years old

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Re: No spark at plugs

Postby JFB » Thu Jun 04, 2015 8:25 pm

I did check the rotor does turn but there is a good bit of slack in the mag pinion gear. Could this cause no spark at plugs? The coil does produce a great blue spark if I hook a spark plug wire with a plug grounded to it.

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John *.?-!.* cub owner
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Re: No spark at plugs

Postby John *.?-!.* cub owner » Thu Jun 04, 2015 9:56 pm

Check the rotor for stripped teeth. Take a look at this.
viewtopic.php?f=140&t=83108
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Re: No spark at plugs

Postby Rick Spivey » Fri Jun 05, 2015 4:40 am

The pinion gear is typically the wear part, so if rotor teeth are intact, a new pinion gear will likely remove most slop. The slop will not cause a no spark condition, but could affect performance, as it could cause erratic timing of the spark. Both rotor and pinion are available from TM Tractor Parts, Steiner, etc. but be prepared for sticker shock.
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Re: No spark at plugs

Postby Cecil » Fri Jun 05, 2015 7:46 am

If you have that kind of spark and it now won't run I would expect timing. I would go with the posts above and suspect the pinion or rotor. If they are bad I can come up with some good used ones for you.

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Re: No spark at plugs

Postby mva1958 » Fri Jun 05, 2015 8:34 am

Did you set the point gap at .13, which is the correct gap for mag ignition, or at .20 like the kit instructions usually say?

Also, make sure the little plastic insulator that snugs up against the distributor wall at the point spring anchor is intact; if it's compromised it will send the spark to ground.
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John *.?-!.* cub owner
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Re: No spark at plugs

Postby John *.?-!.* cub owner » Fri Jun 05, 2015 9:03 am

I am getting old and not reading as careful as I should, I just now noticed the old rotor/new cap comment. I once put in a new rotor and an aftermarket cap, and the arm on the rotor hit one of the contacts on the cap and stripped some teeth on the rotor. I was not a happy camper.
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Re: No spark at plugs

Postby JFB » Fri Jun 05, 2015 2:22 pm

Thanks for all the responses. I have been working all day so I haven't had time to recheck the timing. I did set the points at .013. I am gonna try and get back to it this evening.

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Re: No spark at plugs

Postby JFB » Sat Jun 06, 2015 6:28 pm

She's running . I went back and checked the points and apparently I didn't get the points tight and when i put it all together and cranked it they moved . I reset the point gap at .013 and it ran great. I plowed with the belly disc turner today for about four hours. I have an idle issue , the tractor is idling very high so I need to adjust that but she runs great. Thanks everyone for the help.

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Re: No spark at plugs

Postby Glen » Sat Jun 06, 2015 7:52 pm

Hi,
Welcome to the website. If you don't know how to adjust the idle speed, there is a small screw behind the carburetor where the rod from the governor hooks on. The screw should have a spring on it also, to keep it from turning when in use.
Sometimes a Cub will have poor idling because the bushings in the carburetor on the throttle shaft are worn. This lets in air around the shaft, and makes it run poor, especially at idle speeds. You can tell if it's worn by moving the piece with the idle speed screw sideways. If it's worn much, it needs a new shaft and bushings.
I saw one before that had no bushings, just cast with the carb where the shaft was, so I'm not sure how many of them have replaceable bushings.
The Cub owner's manual says to set the idle mixture screw on top of the carb 1 turn open, then start the engine, warm it up fully, and set the mixture again, turn the screw in or out until it runs as good as it will, at low idle speed.
The ones I have done usually need about 1 1/2 turns open. This info is for the IH carb. :)
Last edited by Glen on Sun Jun 07, 2015 7:49 pm, edited 1 time in total.

JFB
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Re: No spark at plugs

Postby JFB » Sat Jun 06, 2015 8:20 pm

Thanks Glen . I will check that tomorrow.

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Rick Spivey
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Re: No spark at plugs

Postby Rick Spivey » Sun Jun 07, 2015 6:22 am

When setting the idle "mixture" screw, be aware that it is metering the air, not the gas. So in is rich, out is lean. Set it so there's no black smoke at idle, and when you "blip" the throttle to fast idle by hand, it should run up in rpm's crisply without stumbling or hesitation. That is as good as most will adjust.
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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