Guys I get bad farts and backfires from my carb if I don't run with some choke on. It is a stock HD carb. I have no idea what jets are in it or how to even know. I did replace the accelerator diaphragm that was torn and it runs better but still get some farts. It runs great at idle but the sec I take off from a stop it almost dies without choke. What the hell is up?

 

If it idles ok without the choke engaged, then that part of the circuit(Idle) is fine. When you add throttle, that action brings the vacuum piston/slide into play which raises the needle-jet (mid-range circuit). Everything between Idle and WOT is controlled by the needle-jet At WOT the main-jet comes into play and provides all fuel required. The problem you describe would be in the mid-range circuit. The choke cuts-off air to the gas mixture...making it richer and easier to ignite. When it will only get a good mix to fire with the choke engaged the mix is too lean. Getting more air than atomized-gas. Could be water in gas, dirty needle-jet passage, faulty vacuum piston/slide, vacuum problem, weak spark.....iow, a detective story. Hope this helps some.....

 

Can I suggest less beans in your bike's diet?

 

There is a soft solder plug on the bottom back side of the carb. If its still intact, it needs to be drilled out so you can get to the mixture screw. Once you get to it, GENTLY turn that mixture screw all the way in till it seats. Then back it out 3 full turns. If the problem improves but you still get an occasional fart, turn it out a tad more. Never more than 3 1/2 turns total. If that solves it your done. If that does not solve it then you may have other issues or simply need to run larger jets. The fact you have an S&S bottom end would lead me to believe your engine is no stock and might need to be rejetted. But try the adjustments first.


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Can also add gas-x to the tank to get rid of the farts

 

Mine did this when I was lean, I drilled out the plug, put an EZ Adjust screw in, and tuned it in, no more issues

 

Thanks guys I will have a look for the mix screw. It does idle perfect with no choke. This is a newer issue. I just got the bike in April and it ran great then a month or so ago I have this backfire. When I raise the slider it sounds like I have good vacuum so that diaphragm is good. This farting sucks it's embarrassing at a stop light and having your bike cough and sputter trying to drive away. The S&S lower is just the case I think. It is a stock Harley upper. The old guy I got it from did not know much about it. He bought it to ride to sturgis with his wife once then it sat for years.

 

You might try something like Seafoam in your next tank and run it really hard. The jets can get mucked up, and sometimes the ol' Italian tune-up will help. Or it could need cleaning.

 

If the issue is new then its probably not the jetting or mixture. Almost always with carb'd Evo's its an intake manifold leak. Super easy to check. Start it up, let it idle and spray WD40 or carb cleaner where the manifold bolts to the head. If you get an idle change, its sucking the stuff in... which means they are leaking. Very common problem and takes but a couple hours to install new ones.


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I have tried a lot of sea foam in the tank and the deep creep sea foam spray into the carb and blew a ton of white smoke out. Still nothing. Then put a new non torn accelerator pump diaphragm in. Ran better now it is farting more still. I will have a look at the intakes. Would it make sense for those to be metal? On minethey looked metal or I could be seeing **** lol! If all else falls beano it is. Funny story my wife as a joke put some of that in my Christmas stocking years ago and I tried it just to see if it works and it does. I drank so much beer ate a ton of pizza and for the life of me could not fart!!