I have an 84 Ironhead. I just had the top end rebuilt, new leads and coil and timing.My problem is my bike is running good till i go wide open. Then it starts to studder or miss like its over loading or too rich. If im just cruising, itll go to 65mph and thats it. Then its starts its studdering ****.Im not sure of the problem and could use some desperatley needed advice/help.

 

you have no real info to get help - what carb / what ignition / oem or ?????? / how old is the fuel in it -- kind of info helps

 

Stutter and miss sounds to me like lack of fuel. Check the float level in the carb bowl. I'll bet you a beer that it is set too low

 

Sorry, late Keihin carb, OEM electronic ignition (breakerless). New gas, just filled up.
Float height is a possibility, but it just started doing it. Had no problems with it before this.

 

What rev limit do you have your new electronic ignition set at. I set mine way to low after installing it. Mine did just what you say your bike is doing. I turned up the rev limit so it would allow a higher rev from the engine by resetting the switches on my ignition board. Then my bike ran like a raped ape being chased by a much larger in heat gorilla. He hasn't caught my bike yet.

 

Its OEM, like a distibutor. Its doesnt have a rev limiter. Before this crap started, it wouldnt peg out. It would have kept goin till it blew the motor. I never took it that far cause that **** aint cheap, haha. A couple buddies of mine told me to check the main jet...? So now Ive been told main jet, float height, rev limiter, and accelerator pump. And im not trying to
**** with all these and dig myself a deeper hole. Ive gone threw school for motorcycles but im still learning. I have no problem with taking it apart and replacing/rebuilding...its diagnostics thats kickin my ***.

 

Continually taking apart, checking things, rebuilding, & adding stuff are all part of owning a Harley. Hope you get it straightened out.

 

I had the same symptom on my 1980 some years ago. I was some distance from home and once i got up in RPM it would sputter; release the throttle, cost a bit, and it was good again. Repeat.

At the higher RPM it was draining the float bowl. Set up the float and was good to go. It was running fine before this. Not necessarily your problem but it is more likely than the other suggestions.

Here's some notes - note the carb stand, much easier to adjust and test the float level with the carb set up on the bench [my current version uses angle aluminum instead of flat steel - easier to drill the two holes, and more stable].

To test the float i set the carb on the stand top side up and fill the bowl using a small funnel and a couple inches of clear plastic tubing ...

Cleaning a Carb

1. Removing it from the bike should be straight forward. First thing when it is out is to check the pilot screw setting. Turn it all the way in until gently seated counting the number of 1/4 turns; then write this number down; then reset it.

2. I put mine in a vice to remove the screws, and for much of the following work. Wrap in a shop towel; close the vice gently taking extra care with the choke and throttle linkages. The vice is a needed extra pair of hands.

EDIT: This setup works better than putting the carb directly into the vice ...



3. I am very careful handling the float so as to not change the level. I use the official specs for setting the level as in the FM, and check it, every time i dismantle the carb, as the last thing before putting it back together.

4. The jets are made of brass, a soft metal that is easily damaged. Use an exact correct size screwdriver. I ground a medium flat blade screwdriver down to exact size on my bench grinder to access the slow jet.

5. The general appearance of the inside of the carb is not necessarily a good indication of its condition. It can look spotless and have clogged jets, or look cruddy and have clear jets.

6. I prefer to clean each individual part rather than soak or boil the whole carb in carb cleaner. But either way is good. Do not allow any solvents to contact any rubber parts [tip of needle, o-ring seal for bowl].

7. Make a list of all of the jets and passages for your carb using the carb manual or the FM for the bike. Then ensure that you can blow either compressed air or carb cleaner thru each one.

8. Remove the pilot screw and clean the parts and the passage. The passage contains in this sequence: pilot screw, spring, washer, o-ring. These are very small parts, especially the washer and o-ring. Usually the spring will easily fall out. One time i thought the spring was not in there because it would not fall out; i obtained a new spring and could not get it in! The technique for removing the washer and o-ring is to use a pipe cleaner: stick it in the hole, twist it around, remove it - you should see the washer and o-ring on the end of the pipe cleaner.

Remember that the purpose of the washer is to protect the o-ring from the spring and you will always get them back in in the correct sequence.

EDIT: Some carbs, noteably 1966 to 1978 Sportster carbs, do not have the o-ring and washer in the pilot screw passage.

9. Dismantle the accelerator pump assembly noting carefully the sequence and orientation of the parts. Clean and inspect the parts. Replace the diaphragm if it is cracked.

10. Check the float level then carefully put it back together. I personally find it very confusing trying to decide which way to bend the tang if it is not correct. If the fuel level is low is the float high or low? Do i need to bend the tang up or down? On the bench the carb is usually upside down, adding to the confusion. Sort all this out before making an adjustment.

Best to replace the original Phillips screws for the bowl with stainless steel socket head screws.

 

To me it sounds like a to rich situation ,i had the same problem and the jets were to large,but i moved to a higher altitude area 5000 ft ASL. I had to go a far bit down in jet sizes to get it not to sputter at higher rpm.

 

So how about this for the culprit. Yes it was too rich. Was have that established..plugs were black. Now pay attention...the choke plate spring. The spring that holds the choke plate open when the choke is off...its worn out. Its not holding the plate open..there for im getting into fast speeds and im not getting the proper air flow to even it out...so the choke is on and basically im running way to rich and thats why its studdering.