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Offline Jrb4918

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Possible carb issue
« on: March 10, 2015, 08:48:26 PM »
Hey guys, hoping someone might be able to help.  I have a '78 750A, fires right up (with choke), and after warm runs great (no choke).  Then, say 2-3 miles down the road, I lose power.  I've been able to get it home, but noticed that the 1 and 4 cylinders aren't firing.  Spark and compression are fine on each.  Once the bike cools back down, it fires right back up on all 4.  The motor and carbs were completely rebuilt 500 miles ago and it's run since.  I initially was thinking it was the coil, but in that case 1 and4 would never work right?  Appreciate any suggestions.
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Offline goldarrow

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Re: Possible carb issue
« Reply #1 on: March 10, 2015, 09:12:49 PM »
Sounds like classic symptoms of failed dyna ignition. 
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Offline calj737

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Re: Possible carb issue
« Reply #2 on: March 11, 2015, 06:23:07 AM »
Are you running electronic ignition or stock? If stock, check your condensers and if not that, then swap the coils around and verify the problem moves with the coil. If they're stock coils, test them for resistance and inspect the end caps. Might need a trim on the end wires.

As Goldie said, this is also a commonly reported issue with older Dyna electronic ignitions. (If that's your situation?)
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Offline Jrb4918

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Re: Possible carb issue
« Reply #3 on: March 11, 2015, 02:26:20 PM »
It is a Dyna S, was installed when the motor was rebuilt.  Do you think it was defective or is there a fix for it?
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Offline calj737

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Re: Possible carb issue
« Reply #4 on: March 11, 2015, 02:27:26 PM »
Dyna coils too? If so, swap coils and see if the problem follows. If the unit is defective, you might be able to have it repaired...
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'73 500 Build http://forums.sohc4.net/index.php?topic=132935.0

"Of all tyrannies, a tyranny sincerely exercised for the good of it's victim may be the most oppressive. It may be better to live under robber barons than under omnipotent moral busybodies. The robber baron's cruelty may sometimes sleep, his cupidity may at some point be satiated, but those who torment us for our own good will torment us without end for they do so with the approval of their own conscience." - C.S. Lewis

Offline Jrb4918

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Re: Possible carb issue
« Reply #5 on: March 11, 2015, 04:57:17 PM »
Has the original coils on it.

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Offline Jrb4918

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Re: Possible carb issue
« Reply #6 on: March 24, 2015, 09:18:45 PM »
Right on the money guys.  Installed the new dyna today and she's running like a champ.  Thanks!
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