Help me be a hero

Hey, how's everyone doing? I have a problem and hoping to find some help. My girlfreinds father has a '04 1200 sporty with a terrible sputter. The bike starts fine and runs fine for a while. After 10 -15 mins of riding it develops a bad sputter, but only just off idle. It idles fine and if you keep the revs up it runs fine as well. Things I have tried: Doesn't appear to have intake leak, pulled bowl of carb and checked jets and passageways, air filter is good, new plugs, carb diaphram seems good and accelerator pump seems to be operating fine. It has stock pipes, k&n airfilter and the low speed jet has been bumped up. I am stumped! Any help would be much appreciated.

Not a Sporty guy, but maybe electronic ignition module? Seen the same thing on cars, given that it seems you've checked all the mech stuff that you can get to. Electronics tend to fail in heat, especailly balky ones.

The bad news is it is a bit harder to check that if ya can't play swap & test with another Sporty. But not impossible. Does you honey's dad have a tech manual?

BINGO !! My Sportsters are older & I have not personally worked on an '04-up model. But I do know the ignition module hates heat & will screw up getting hot, no matter where it's mounted - "nosecone" in the cam cover, under the seat, or in the triangle cover behind the battery like on my '95 Sportster.

Also, some other simple things can screw up - for example, the spark-plug cables can break inside the insulation & you'll not see it. You can test with a meter.

Thanks for the input guys, I will check out the ignition. It just seems to have me running in circles.

Suprized That's All That Is Wrong With A 04, Did They Change It To Fuel Injection, Can't Remember, Lost Interest After O3. AS FOR THE SPUTTER, THAT REALLY ISN'T THAT UNCOMMON WITH A SPORTSTER, DEPENDING ON THE SPUTTER, MINE DOES IT ALL THE TIME, BUT MINE IS FROM NOT RE-JETTING, IF IT'S NOT FI, THEN IT COULD JUST BE SIMPLE RESPONSE TIME.

2004 was the 1st year for the larger & heavier Sportster frame with rubber-mounted engine, but 2007 models were the 1st with fuel injection.

And the "sputter" with a carbureted Sportster is not that hard to fix. Both my '95 & '00 Sportsters had the "carb farts" when I bought 'em, but $15 worth of carb parts takes care of that. 42 slow, 165 main jets for an 883, 42 slow, 175 main for a 1200, the infamous N65C needle for a 1988 XL1200 for both & 2.5 turns out on the idle mixture screw. There's your baseline.

'04-'06 Sportsters don't need to have the needle replaced & the 1200's tend to need a larger main (180 is the baseline there), but it's not "rocket science" to get the carb to work right. But you have to think "system" instead of individual parts - for example, put a set of open drag pipes on & that'll screw up the tuning. Put a high-flow air-cleaner on but leave the stock mufflers on & that'll mess you up too.

We call it "paying the Harley tax" - the engine can't breathe the way it comes from the factory, but with a better air-cleaner setup, quality "slip-on" mufflers & fairly simple carb adjustments, you can make a Sportster run like a champ & never have the "sputter". Been there, done that, got the T-shirt

Don't know if this will help you much or not but here is the Baseline Chart for carb jets from the 06 Manual (04-06 same bike).

http://bike-talk.com/forum/attachments/motorcycle-tech-talk/903d1208346402-making-sense-jets.jpg

Could it possibly be a crack somewhere that opens up making a leak once the bike warms up?

Good luck, I truly know how big a PITA this can be.

Thanks for all of the ideas guys. It is deffinately not the stock sputter, the bike gets to the point it won't run. He has had the bike for a couple years. The month after he bought it they had to replace the crank sensor. Last spring he had the problem he is having now. After I couldn't figure it out last year he took it to the dealership. They changed the low speed jet and plugs and obviously never rode it. It is deffinately something more. He is frustrated with the bike and the dealership and is ready to give up on both. I won't be able to look at it until next week but if find out anything more I will let you know.

If you think it might be something on the computer side of things, do you know how to run the onboard diagnostics?

Art, The 42 And 165, Is That What Is In There Now Or What Gets Put In, And The Idle Mix Screw, Is This Something That You Have To Put In? I Do Have This Problem With The Drag Pipes And Free Flow Air Cleaner That Needs To Be Fixed.

You should be running a CV40 carb and if so the Idle Air Mixture Screw is under a cap on the bottom rear of the carb. You have to remove the cap to get to it (cap installed once set by factory to meet EPA BS) no need to reinstall it. Will need a small flatblade screw driver to adjust it once you remove cap (usually done by running a self starting screw through the cap very carefully and using the screw to pull the cap out).

Do a search for adjusting CV40 Carb and you should fine all kinds of information on it on the web. Atleast I did when I started all this on mine.

Your bike came with a 42 slow & I believe a 160 main, so all you're doing there is going up one size on the main jet. Idle mixture screw you just have to pull the cap off of to get to.

Just (carefully) drill a little hole down the middle, run a little sheet-metal screw in by hand & using something like needle-nose ViseGrips, snatch the screw out - the cap will come along with it. *Gently* run the mixture screw all the way in, then back out 2.5 turns - there's your baseline. And you shouldn't have to go more than 1/4 turn either way from there - if you do, something's wrong.

Drag pipes are definitely a problem & at least slip-in baffles will help. But the stock pipes with crossover & quality slip-on mufflers like Cycle Shack with give you a wider, smoother & better overall powerband than any other exhaust. I know that for a fact & you can have a look @ my good friend Crim's Sportster exhaust article & dyno charts: The Sportster Home Page

problem

I own a 04 Sport and the problem you are having is the crank position sensor. It is located on the left front on the motor and plugs in on the right under the motor, I don't remember the part number it's cost is about fifty dollars. Replace it now it will leave you soon, you can do the work in about fifteen minutes. Dutch

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Here is the part # H/D32804-04A I am a retired service manager from a multiple brand dealership, I'm telling you this just to give alittle background on this problem. H/D won't admit to this but they had a supplier problem with these sensors so you may still get a bad one from the dealer be sure and keep your receipt. hope this helps Dutch

thank you for the info Dutch. He did already have to change it once and I thought the dealership might have caught it, if it happened again. Once again I appreciate the info.

Just curious, does the bike hold a charge if it sits idle for say a week or so without a battery tender. Al

yes Al, it holds a charge fine