Front cylinder not firing after 3000rpms

[rapatner073]

I have a 2003 american ironhorse outlaw w/ 13000 miles. 107 s&s with g carb. Lately my bike began stumbling under acceleration. I determined that the stumbling occurs after the bike hits 3000 rpm. (i test while in neutral). Prior to hitting 3000rpm the bike runs smooth. Any thoughts?

[Ricky-D]

Maybe you've made some recent changes that could be the cause.

Like a new air cleaner or ignition changes like the timing, or carburetor adjustments.

You know what I mean.

***

[rapatner073]

Hey ricky, thanks for the reply. I have not altered the bike at all since the problem.

[Ricky-D]

Actually I was referring to changes before the problem occurred.

You know, changes that may have caused the problem!

***

[rapatner073]

Right, I meant to write prior to the problem. Im thinking bad coil or ignition... any idea where the ignition mod is loacted? What you think?

[Batto]

The module is in the front of the nose cone be hind points cover 2 small screws in cover. Have you changed plug leads to rule out the leads,plugs,etc.

[rapatner073]

Yes, I changed the plugs and ruled out the leads. Could the ignition switch be the problem?

[Ricky-D]

You say the motor stumbles while at a fast idle (3000 rpm's)

No load on the motor.

I don't consider there is a problem actually.

The fuel system is still functioning on the idle circuit at that point, you've hardly got the throttle open.

I'd say that's pretty normal, the motor is just trying to get up on the cam and there's no load on the motor so the fuel is only minimally adequate.

You could try increasing the fuel supply at that point with a turn or so of the idle mixture screw. (a little more rich)

***

[rapatner073]

so i was messing with the bike this morning. if i ease the throttle up to 2900 rpm it's fine. as soon as it hit 3000 it falls on its face. now if i crack the throttle from idle, it immediatly stumbbles. does that change your thinking at all? thanks for your patients with this. this shit amkes me want to sell the bike...

[Ricky-D]

Trying to do an analysis with no load on the motor is not very helpful sorry to say.

When there is no load on the motor it will easily loaf at the upper rpm ranges and emit all kinds of false information.

If it were me the first thing I'd do is index the throttle and star riding it to see if the is any kind of problem.

To address the change you notice from a very minimal change to the rpm's would indicate a problem with the ignition module but even this is questionable since there is no load on the motor.

Index the throttle and go from there.

***

[rapatner073]

I had it on the highway today and she cruises steady at 60 mph w/o stumbling. As soon as I get on the throttle it stumbles. I basiclly had to accelerate slowly through the gears to get up to 60-65 mph. If I accelerated to hard it would stumble.

[Thompsongunner]

I would take the bowl off of your carburator and check it. I had the exact same problem and it turned out to be a few large brown pieces floating in the bowl. I am thinking that when i would crack the throttle pretty hard, it would pull one of those pieces against the bottom of the main jet and block it. If I would roll on the throttle real easy when riding, I would have no problems as you mentioned. I would bet you have a clog somewhere. My accel pump worked fine and while stopped you could rev it and all seemed fine until you rode it. If I was riding along around 50 or sixty in a higher gear and would just give it full throttle, the bike would all but shut off. Now after cleaning the carb, it just pulls and pulls real hard like it should. Give that a try...it only takes 10 or 15 minutes. You can get it off without taking the carb off the bike. At the very least remove the large brass screw from the bottom of the carb. Be carefull as all the gas in the carb will run out so have a large rag or something to catch it in. Oh and turn the gas off at the petcock too. I made that mistake already! Good luck. Dan