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Discussion Starter · #1 ·
My dad has had it for 20+ years and had rebuilt the motor about 5 years back. It has new piston rings and a new piston. It hasn't ran much since then and has maybe 50 miles on the new rings. I just got it running a few days ago and it's emitting white smoke out of 1 exhaust pipe and backfires in the same pipe. I just put in fresh oil the day I got it running and it already looks black. And even after repeated cleaning the new plugs are also always blackened. Any insight on what could be going wrong with it would be really helpful. I'm pretty new to working on Harleys so I don't know a lot. Thanks for your time.
 

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Discussion Starter · #7 ·
Both plugs look the same after running for a few minutes. Sooty black. I don't have a lot of experience with S&S carbs but I've been reading manuals about how to adjust them. I jetted the intermidiate from 0295 to 028 and the main jet from 72 to 66. It did nothing if not made it slightly worse.
 

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Hmmm...I think I'd try turning the idle mixture screw all the way in (gently) and see if the bike will start. This will lean it way out and it shouldn't start. What can happen sometimes is a ham-handed mechanic can turn that screw all the way in and the point will start to wallow out the opening and that will cause the bike to run rich all across the range. You can also check the same thing by turning the screw all the way in while the bike is running and seeing if it cuts off and dies at idle.

I'd also do a compression test, just to eliminate that possibility even though the bike has new rings.
 

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To add one on that I would double check the ignition is spot on before diving any further into the carb.
 

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Discussion Starter · #10 ·
Well I messed with the idle screw and it's running a bit better. I took it up and down the road 2 times and the top end is pretty good. No sputtering or backfire. When you get off the throttle and the engine revs down it backfires a few times. The low end is all sputtery and jumpy. I've been wondering about the timing because the Kickstarter will kickback every once in a few starts.
 

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Personally I don't like trying to tune a carb unless I'm sure everything else is spot on.. Ignition timing, valve clearance, compression, etc. Carbs come last.

If you're not at the drag strip then yes, drag pipes aren't the best option. They sound cool though!
 

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^^^ Right on.

Also, an open exhaust will cause even the best tuned bike to backfire when you let off the throttle.

Like the Man said, I'd check everything else relevant first and then tune the carburetor.

And going back to that, what I do on those is set the idle then turn the idle mixture screw in slowly until it start to sputter. Back it out slowly until it runs fine, than starts to sputter again. Count the half turns as you're doing this. The figure out how many half turns is between the two extremes you just found and park your screw there. You can then do some roll ons and so forth and get to your accelerator pump and what not.
 
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