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Cub starting issues
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- 5+ Years
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- Joined: Fri Jun 19, 2015 5:18 pm
- Zip Code: 53010
Cub starting issues
I have a 1946 cub runninh on a 6 volt system. I am having trouble with the tractor starting. If you pull the choke when trying to start it gas will pour out the bottom of the carb. It will sound like its going to fire but is difficult to get it going. If you pull it it fires right up and once it's started you can usually get it started again. The carb has been cleaned and the magneto has been timed to the best of my abilities. Once the tractor is running it runs great, I'm just not sure where to start! I don't want to spend money on things I don't need any help would be appreciated.
- challenger
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Re: Cub starting issues
The first place to start is to perform a compression test on all cylinders. Make sure to blow the debris out of the spark plug depressions around each plug after you loosen but before you remove each plug. Remove all plugs, and with the plugs out crank the engine over with the starter and do a dry test of each cylinder and record the readings. Then squirt some oil in each cylinder and take the wet readings. You hope to find fairly uniform compression readings across all cylinders around 100 psi. Let us know what you come up with.
- Bus Driver
- 10+ Years
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Re: Cub starting issues
A different starting procedure would be to turn on the magneto, pull the starter rod with the right hand and if the tractor does not fire quickly, pull the choke rod with the left hand while continuing to actuate the starter. Push in the choke rod as soon as the engine fires. Further experience may indicate a need for longer partial choke application in colder weather.
Luck favors those who are prepared
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Re: Cub starting issues
Timing light. You can use a 12 volt timing light with a 12 volt power source.
Check the magneto's firing on #1 cylinder at engine cranking speed. Magneto needs to fire at TDC, #1 cylinder at engine cranking speed.
Suspect magneto's timing is off a bit. That's the reason engine starts when tractor is pulled.
Check the magneto's firing on #1 cylinder at engine cranking speed. Magneto needs to fire at TDC, #1 cylinder at engine cranking speed.
Suspect magneto's timing is off a bit. That's the reason engine starts when tractor is pulled.
I have an excuse. CRS.
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- 5+ Years
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Re: Cub starting issues
I checked the compression a few months ago and it was fine. The tractor is usually started by pulling the starter and pulling the choke, but I'm not sure what you mean about starting the magneto before starting the tractor? I have not used a timing light but I also suspect the timing might be off. I tried to time it to the best of my abilities. Usually after I'm at tdc and I have the magneto on I turn it slightly till it clicks but I'm unable to do it on this tractor because of the top bolt placement.
- Trent M
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Re: Cub starting issues
I concur with the timing light check. Its common for gas to come out of the leak hole of the carb when trying to start without success. Personally, I found that hard starting was almost always due to timing was off some. And in your case, if it is running fine after a pull-start, I'd bet timing is your issue.
Trent McPeak
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Re: Cub starting issues
As soon as I get a chance I am going to try and time it again and I will let you know how it goes. Because I can't rotate the magneto after ruff timing it to get the impulse Cypher to click over I'm not sure what I'm going to do yet but I'll try and figure it out. Thanks again for all the help!
- Glen
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Re: Cub starting issues
Hi,
Welcome to the website. You probably need to buy a timing light, and check the timing, like they said in the above posts. It's important that the timing is right so the Cub will start good, and have power when running. A lower priced timing light should be ok, maybe not the cheapest one though, depends on how bright the light is that it makes, you don't want a dim light.
Also, they didn't make Cubs until 1947, you can get your serial number from the plate by where the steering shaft goes into the steering gear, and look at the top of the page here, and you can figure out the year the Cub is.
Welcome to the website. You probably need to buy a timing light, and check the timing, like they said in the above posts. It's important that the timing is right so the Cub will start good, and have power when running. A lower priced timing light should be ok, maybe not the cheapest one though, depends on how bright the light is that it makes, you don't want a dim light.
Also, they didn't make Cubs until 1947, you can get your serial number from the plate by where the steering shaft goes into the steering gear, and look at the top of the page here, and you can figure out the year the Cub is.
- Bus Driver
- 10+ Years
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Re: Cub starting issues
My comment about the magneto was intended to indicate that one must not forget to set the magneto switch to the RUN position. When Cubs were introduced, virtually all vehicles used separate arrangements for the control of the ignition and of the starter.
Luck favors those who are prepared
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Re: Cub starting issues
Bad/weak impulse coupler?
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Re: Cub starting issues
viewtopic.php?f=1&t=87385&p=695938&hilit=magneto+drive+gear#p695938
Above link, a discussion on magneto and governor timing. There are a number of topics on this site, with photos, on the topic.
Suspect the magneto drive gear is not properly positioned. Probably off one tooth, limiting the magneto's rotation.
Above link, a discussion on magneto and governor timing. There are a number of topics on this site, with photos, on the topic.
Suspect the magneto drive gear is not properly positioned. Probably off one tooth, limiting the magneto's rotation.
I have an excuse. CRS.
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- 5+ Years
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Re: Cub starting issues
So after more research I believe that the top stud that holds the magneto on was not original. This is not allowing me to rotate the mag to have the impulse coupler click over after timing it. Hopefully i will get time this weekend to work on it.
- John *.?-!.* cub owner
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Re: Cub starting issues
I am going to make a guess that you have always had this problem since owning the cub, or since someone has had the governor, front cover off, etc. Loosen the magneto clamps and turn the top all the way toward the engine head. Set the engine to #1 (front) cylinder at top dead center and the mark on pulley lined up with the pointer on block. Turn the magneto away from head until impulse snaps, and tighten clamps. If you cannot turn it far enough to get it to trip, most likely the governor or idler gear is out of time. When a cylinder is at TDC center the drive slots should be in this position. If not one of the gears is out of time.
Since the crank pulley on a cub shipped with a magneto only has one timing mark any timing light you use needs to be one with adjustable timing.
Since the crank pulley on a cub shipped with a magneto only has one timing mark any timing light you use needs to be one with adjustable timing.
If you are not part of the solution,
you are part of the problem!!!
you are part of the problem!!!
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- 5+ Years
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- Joined: Fri Jun 19, 2015 5:18 pm
- Zip Code: 53010
Re: Cub starting issues
Thanks for the picture. I was watching a YouTube video everyone was referring me to and it looked like he was rotating the mag on the governor and the top stud you show in your pic wasn't there. I will have to do some work tomorrow and look for clamps. I am fairly mechanically inclined but am new to the older tractors. I'm trying to get all my grandpas tractors running, a 8n, farmall A, and an allis B are as far as I've got still have the cub an H,C, and a ford 860. Lots to do! Thanks for all the help.
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- 5+ Years
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- Joined: Fri Jun 19, 2015 5:18 pm
- Zip Code: 53010
Re: Cub starting issues
[quote="John *.?-!.* "Turn the magneto away from head until impulse snaps, and tighten clamps."
How do you rotate the mag when the top stud is stationary? Mine is the same as the one pictured above. I know some had a bolt with a clamp on the top and I have that on my A and I managed to time that but with this top stud I can't get it to rotate.
How do you rotate the mag when the top stud is stationary? Mine is the same as the one pictured above. I know some had a bolt with a clamp on the top and I have that on my A and I managed to time that but with this top stud I can't get it to rotate.
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