I just rebuilt the carb and accelerator pump(S&S Super E) on my 1980 FLH. It has a cam and solid lifters in it..

The problem is when I blip the throttle it is still hesitating and back firing through the carb and sometimes shoots out a flame. I adjusted the carb per the instructions from S&S. It idles find and seems to go fine under light throttle. The issue seems only only under hard and fast throttle.

I'm basically looking where to go from here? Could the lifters be out of adjustment and cause this? Could it be timing? Or possibly even the accelerator pump is not working properly??

 

I would check the pushrods just to be sure, but it sounds more like timing and/or accelerator pump to me. I have a small flat spot with my E also, but its not bad at all. It doesn't backfire though. The overlap on the cam may be causing part of your problems. What kind of ignition are you running?

 

Looks like stock ignition to me...
Coil is stock, the guy I bought it from recommended putting a high performace coil on it.

 

If the backfire appeared after you rebuilt the carb and did not exist before hand, I would suspect the accelerator pump. I would also check for any vacuum leaks in the intake. Did you replace the rubber bands? (you should)Make sure they are fully seated against the heads and intake manifold. Also make sure one of the band clamps isn't cockeyed.

 

It was backfiring through the carb previously and had that hesitation under hard acceleration that is why I rebuild it. It made a difference in the way it runs but it didn't fix all of the problems..
I will check the intake and band clamps for leaks.
Are the rubber bands under the band clamps?

 

Somebody help me out here, isn't it, backfire thru carb = lean, backfire thru exhaust = rich, or is it the other way around? So maybe if this is a chronic problem, go a step on the main jet in the right direction. I was thinking if ya have points it might be time to touch them up but an '80 should have electronic igniton, I believe. I don't think replacing the coil will do anything but lighten your wallet, unless yours is bad/flakey, etc. Just another $.02 worth, YMMV, etc.

Bob

 

Backfire thru the carb is lean, try larger main jet, check adj. on acc. pump!

 

Ok... Well, I just changed out my petcock yesterday because it would not run under "ON", only under "Res" which is not good...
The bike sat for some years before I got it... for precautionary purposes I put an inline fuel filter on incase there was some junk in the gas tank left afer I cleaned it out. Well, I noticed that the filter looked pretty dirty... I think that gas was really getting restricted because of it. It would barely run after I put the stuff back on because of the filter. Could the backfiring be caused because it is starving for gas?

Also I see posts about setting the timing via Static and Dynamic... how are these done?

I would like to make sure all of fine with that also this weekend. I found instructions on adjusting the lifters which will also be done this weekend... BTW thanks for all of the input so far!!

 

Back firing through carb is indication of a lean mixture. Besides correcting your petcock/fuel filter problems, I would definitely check and fix any air leaks. Also, make sure your gas cap is venting properly. I would also double check the adjustment on your lifters.

Static timing on points can be easily done with either a piece of paper, or better yet with a 12v light bulb. Static timing, however,will onlyget you close to where you should be since this sets the retard timing only. Dynamic timing with a timing light will get you spot on. This will also verify that your advance mechanism is working properly.

To static time:

1. Get a service manual - look under the post: "I need a book" in this forum. That posting has links for youto download a complete service manual for your bike.

2. Pull your spark plugs tomake it easier to turn over your engine. This will also prevent your engine from accidentally starting while you're turning your engine over.

3. If you have a kick starter, it'll make it easier to turn the engine over to get to the exact spot. If not, you might need to lift your bike and use the rear wheel. I run a belt primary, so I usually turn the engine over by turning the crank sprocket.

4. Remove the timing plug and screw in a clear timing plug (buy one if you don't have one)so you can see the timing marks without getting spat on with oil.

5. Set the frontpistonto top-dead-center (TDC) on its compression stroke. Don't confuse the Advance mark with the TDC mark. Depending on your bike and motor, it can either have 2 or 3 timing marks (the 3rd is the rear cylinder advance mark)since Harley screwed around with the timing markings over the years. Refer to the manual to see which timing mark is applicable to your model/year. Toverify TDC,look in the timing hole to see that the TDC mark is in the middle of the hole.

6. Now go to the timing plate and connectone lead of a12v light bulb (with alligator clips) to ground. Connect the other to the hot side of the points.

7. Turn on your ignition switch. But don't turn the engine over. Otherwise you will need to set TDC on the front piston again.

8. At this point, the light bulb may or may not light up.

9. Loosen the point's timing plate screws just enough so you canrotate it with your fingers (or a flat blade screw driver against the timing plate adjusting dog), butwith some resistance.

10.When you're rotating the timing plate back and forth, the light should be going on and off. Set the timing so that the light is just coming on. Then tighten the timing plate screws. This should get you the approximate timing you'd need to start and run your bike so you canset amore accurate timing with a timing light.

Dynamic timing:

1. Beg, borrow, or steal a timing light. If you steal one, don't get caught. If you borrow one, make sure you give it back! Begging is degrading unless it's for sex with a hot babe. Even then, it better be worth it!

2. Hook up the timing light.

3. Swap out the timing plug with a clear one so you can see the timing mark. If you have a dry clutch - belt primary, Iprefer to make a reference mark on the alternator rotor withWhite Out (after you've set your flywheel at the properadvancemark)and an anothermark on the inner primary cover. Thiswill let you flash the timing light through theouter primaryinspectioncoverhole, and see the timing much better instead of looking through thatlittle clear timing plug and a film of brown oil. It's a little extra effort, but

 

Oh ya. Make sure you swap out theclear timing plug with the real one when you're done. It's only plastic!