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Discussion Starter · #1 ·
I have a S&S 7080, I put points on my bike.. When I go to start it, it backfires so loud it literally, shakes the place. I can’t seem to figure out how to get it right. My dream was to have a Harley and I swear I feel as if I am cursed, it is one thing after another.
 

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7080? I don't recognize that engine type. Is that an older one, or maybe the part numbers on the cylinders? I'm guessing 80 ci? Anyway...

First, have you done anything to the cam or pinion gear? Are you just replacing a points set or are you replacing an electronic ignition?
 

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Discussion Starter · #3 ·
7080? I don't recognize that engine type. Is that an older one, or maybe the part numbers on the cylinders? I'm guessing 80 ci? Anyway...

First, have you done anything to the cam or pinion gear? Are you just replacing a points set or are you replacing an electronic ignition?
It is older it is 93.. nothing done to cam or pinion gear. Replacing electronic ignition.
 

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I'm hoping the timing marks on that flywheel are the same as on a Harley motor, but I don't know if they are. If not, you might have to call S&S and ask them what sort of marks you have. Anyway, I would go back over my installation and check each detail, like so:

First, gap your points. .018 to start, unless you have something that specifies a different gap.

Rotate the engine until you see the static timing mark line up with the timing hole. Straight up and down. Your timing mark should be a straight line, (I hope,) that follows a dot that indicates top dead center.

Rotate the mechanical advance until it is at full advance.

Loosen the points plate hold down screws just slightly and rotate the points plate until it just starts to open. Barely starts to open. If you're using a test light that is until the light goes out. Tighten down the screws and that should be close enough to get you running decently. You can then rotate the points plate very slightly in either direction to fine tune the ignition, but usually that's not necessary.

If you're still back firing and running rough, check your advance unit to make sure the weights move freely and nothing is binding up. You can try experimenting with your points gap too. Anything from, say, .012 to .020. Obviously make sure everything else on the engine, fuel and intake and so forth, are right too.
 

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Is it possible to connect the points backwards on that bike?

Single or Dual fire coil(s)?
 

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Honestly I don't know if it's possible on what you're working with. Is there one or two sets of points there?

I work on a lot of metric bikes and if you get the point connections swapped it will do exactly that. Just trying to think of easy things to check.

Have you worked through things as Eye layed out?
 

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Discussion Starter · #8 · (Edited)
Honestly I don't know if it's possible on what you're working with. Is there one or two sets of points there?

I work on a lot of metric bikes and if you get the point connections swapped it will do exactly that. Just trying to think of easy things to check.
I don’t know, to be honest, unless you can tell me how to check. I am just teaching myself how to do it all.
 

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They usually have two lobes. One for each cylinder. That's why you look through the timing hole on the other side of the engine cases and make sure your timing mark is visible, so you know you're on the right stroke on the front cylinder when you set everything.

There should be just that one wire that leads up to the ignition coil.

In the picture above you're almost all the way to one side with your adjustment and you're missing one of the plate hold down screws. It's possible that missing screw could allow the points plate to move when you don't want it to.
 

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Interesting. I think you need to investigate which flywheel marks you should be looking at now and go through the timing procedure again as suggested above.

Is the bike trying to start at all, or just turning over and giving you really loud backfires?

Interesting project - stick with it and you will get through it!
 
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