I don't know how to check the ignition without replacing but I'm thinking falconbrother is probably right and it is an ignition problem.

 

Engine should be warm and you should get about 120 on front and rear cylinders.

The most important part is that you shouldn't get more than 10 psi difference between the cylinders.

 

okay great. Thanks for y'alls quick responses. I will check compression and check into the ignition and let you know what happens. I really appreciate it.

 

I would be sure it is not dirt in the carb. As it seems like this problem started after you got gas. If not you might find this thred usefull, ignition module can be checked apparently there should be something in the manual.
https://www.hdforums.com/forum/evo-c...nd-info-4.html
Cheers

 

Let's look at it this way; First off the bike was running just fine, then all of a sudden after a fill-up it started to run poorly and you diagnosed "bad gas" which was probably a good/correct guess.

Like all things now days in the obomination deterioration is rampant (can't even get a decent King cake for Mardi Gras this year); but I digress.

When you apply more throttle to do the same "work" the engine has to burn more fuel just to keep up, thus really enrichen the mixture inside the cylinders. This I believe leads to carbon build-up and your problem.

Before tearing the engine or carb apart I would try something like "Star-Tron" in a tank of fuel and see if that helps, Harley also makes a great carbon cleaner additive. I've used both, but now use the "Star-Tron" exclusively because of cost and it also takes care of the ethanol/water problem down here on the Gulf coast.

Just my .02

 

Odds are good it's the ignition module. If you can swap it out with a working unit you'll have your answer.

Also may want to check for an intake leak.

 

From the symptoms you describe, it's the ignition module. Easy fix. Should be a black box under the seat. On the older ones, you'll probably have to wire it in, behind the timing cover. I had to on my wife's '89 Softail. It's been a few years, but I think it was 4 or 6 wires, should be color coded. I think the newer bikes just plug in. Still, it's an easy fix. Also, JohnnyC gives some good advice. I think your '85 would have the compliance fittings (rubber intake manifolds). Check them for leaks also.

 

Before you spend money on an ignition system, make sure you don`t have an intake leak. Backfiring through the carburetor is a symptom of a lean mixture.

 

Yes, check the rubber compiance fittings behind the carb first. If you remove the carb and press around on the fittings, you can probably see a split in the rubber if they are leaking.

 

you can check for leaks without pulling the carb , propain hand held unlit bike ideling run it acrodd the intakes if idel goes up you have a leak , or wd40 will do the same just makes a mess