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TOPIC: 72 AT2 gets dies when warm

72 AT2 gets dies when warm 31 Jul 2018 18:21 #1

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Hello all. My 72 AT2 will start right up and run well for about 10 minutes. After that I can feel it start to miss and if I let it idle, it will die. After about 15 minutes it will crank up and do it again. I thought maybe it was seizing, but I can kick it over when this happens and it did it again with premix added. I've charged the battery and checked the petcock flow. Any other ideas?

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72 AT2 gets dies when warm 31 Jul 2018 22:26 #2

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You need to check the battery voltage with the engine running. The ignition is powered by the battery, so you should see 12-13+ volts at idle and up to 14-ish with the engine revved up. If you test and have low 12's or less, your charging system isn't working.
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Allrighty Then

72 AT2 gets dies when warm 01 Aug 2018 12:17 #3

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I tested and the charging system wasn't working. A few years ago I took it all apart to do the brushes and didn't rough up the copper on the magneto. I remember it being dark and having a waxy film on it. I thought it was there to protect it and left it alone. I'm dreading tearing all that apart again. It was a miracle that I got the timing right. Dave helped me a lot on this forum when I was working on it. I never rode it enough to figure out it wasn't charging I guess.

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72 AT2 gets dies when warm 01 Aug 2018 12:40 #4

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You won't change the timing removing the stator, but does the electric start work? If the electric start works then your brushes are OK. The itty bitty contacts in the voltage regulator dirty up just like ignition points do, so that could be your problem. if the electric start doesn't work (assuming the e-start is all hooked up), then you'll need to remove the stator and clean the commutator, and re-check the brushes to make sure they move freely in their holders. You can do a search of the forum about how to clean the commutator, and on the internet, as the procedure is common and not too difficult. It's not necessarily 'roughing it up" but cleaning the plates, and the grooves between each plate.

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Allrighty Then

72 AT2 gets dies when warm 01 Aug 2018 13:27 #5

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The electric start does work. I got 12.7 testing the regulator wire while running. The red wire was still connected, so the cutoff may be reducing it, duh. I'm going to disconnect it and try again when I get another plug. When I was trying to figure out why it was dying I added premix to rule out seizing. With the oil injection doing its thing, it has fouled the plug.

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72 AT2 gets dies when warm 01 Aug 2018 14:07 #6

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Sounds like you're heading the right direction.

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Allrighty Then

72 AT2 gets dies when warm 01 Aug 2018 14:25 #7

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The regulator was kinda jumping everywhere. 18v to 4v. Maybe I need to clean the contacts?

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72 AT2 gets dies when warm 01 Aug 2018 18:33 #8

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Can't hurt. There's a service manual in the Tech Library using the link at the top of the page. Check out the section covering voitage regulator testing and adjustment.

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Allrighty Then

72 AT2 gets dies when warm 02 Aug 2018 16:34 #9

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I ran the regulator screw in about one and a half turns, changed the plug and tested the battery with it running. It jumps around from 12.5 to 14.7 pretty crazy like. That would confirm what the regulator was doing too. Any ideas what would cause this?

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72 AT2 gets dies when warm 04 Aug 2018 08:08 #10

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Can someone tell me where the second small wire goes that comes out from behind the stator? It's small and braided green with blue tape on it. I have it connected to the 3rd post and I think that may be wrong. I cleaned the commutator, regulator points, and all the ground and still no charge. Big thanks.
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