went for a ride yesterday and all was good then on way back bike started running like crap like on 1 cylinder so i got home changed plugss still the same changed single fire ignition to a brand new one same issues changed plugg wires same issues drained S&S super E bottom drain plugg same issues set static timing same issues . i sprayed some carb cleaner at manifold and found a rear cylinder air leak at manifold. could it be that small leak making bike act up or could it be possible crap in the carb.i'm gonna pull that off today and disamble on another note when its running on 1 cylinder if i rev it up it runs on 2 ?? sure has me stumped. any advice is appreciated
Dave

 

It could be either or both (Iknow that's not much help!!), they both can cause the symptoms you described along with a few other things. I'd figure the manifold if it's the same cylinder missing. If it jumps from one cylinder to the other then the carb.
John

 

Coil is usually the cause of running on 1 cylinder around idle and runs on 2 cylinders when giving it some throttle, battery voltage is lower at idle and it must affect a weak coil, engine revs up and voltage is raised and it hits, the only explaination I can think of for a coil doing this.

I had this happen and was a coil, found my problem by pulling a plug wire off and starting it, front spark was blue and rear was yellow during idle. 2 seperate little coils in that housing and yellow is weak. Mine did it at all times but electrical items usually start failing with heat so something else to keep in mind during diagnoses

 

If you know there is an intake leak I'd fix that before worrying about anything else, or doing anything else.

 

Gotta agree with JohnnyC, Fix the known issue and go from there. Once you get rid of the manifold leak, then look at the coil, then clean the carb

 

yup guys thats exactally what i did it has a Ram jet intake so i had to make my own gaskets out of gasket material and then cleaned the carb real good and she runs great now . i prolly didnt have to change the coil and ignition and plugs and wires but as we all know its process of elimination .thanks for all the advice and i hope what i had to do will help someone elase with a similar problem
thanks to all
Dave

 

ps forgot to mention there was only 1/2 the gasket on rear manifold so it wasnt alittle air leak and that explaines why poor idle > glad i found it before i fired a piston from being too lean >>yikes thanks everyone

 

Glad to hear about you finding the fix!

Heck with both my charging system and my ignition system I started with the cheapest part it might be until I wound up fixing them. It was all for the best on a 25+ year old ride. They are all new now and I know the systems really well.

 

thats what this bike is also johnny C its a 1986 FXR and trust me i been thru most all of it when i bought it 6yrs ago >> new stator new Carb , new belt, new swing arm axle shaft,ignition. and various other ****. funny how it was running perfect yesterday then on way home the intake gasket let loose and not many riding days left up here in Michigan. i have 8 Harleys most are new but i do like riding this ole girl prolly cause i been thru it inside and out lol
Dave

 

It would be nice to have a "stable" of rides. Only Harley's I ever rode were either rentals or this one. Well 1 exception was a short trip down the road and back on a buddies bike to show me they weren't all top heavy like the FLHTCU I had rented the week before.

I probably should do the "preventive maintenance" thing and replace my seals and gaskets before they give me issues. I'm surprised they have held up after all the carb work I've done this past summer.

And as for riding weather, I got out twice for a couple hours each ride yesterday and then noted that the frigid weather was coming in today. I'll get out in the mid 40's and higher but I won't spend a lot of time when the wind chill is in the 30's or below. I polished her up in the warm garage today and called it good.

Not sure where you are, here in Michigan, but maybe someday our paths may cross. See you down the road.