Loses Power

[straightshot]

I have a 2004 1200 that starts right up and runs strong...until recently. It has 12,000 miles on it. After riding for around 20 minutes it starts to stumble with a loss of power. It doesn't die and will idle fine but try to accelerate and it acts as if it's about to run out of gas; has plenty. After sitting long enough to cool down it will start right up and run for another 20 minutes. Any ideas? I'm bringing it to the indie shop tomorrow but they are more big twin than Sporster oriented. TIA.

[NLXL]

Start simple:
1). Check filler cap. Loosen it a bit when it starts to stumble...it could be drawing a vacuum in your tank due to clogged ventilation hole.
2). Check clogged fuel filter in petcock.

[IXL2Relax]

Has any work been done on the bike just before the problems occured?


A heat related issue can occur on the Coil - You can pre-heat the coil on a cold engine (with a hair dryer) & see if the symptoms start right away...

The CKP sensor can also act up from heat.
Here's the Sportsterpedia section on the CKP & other Sensors:
http://sportsterpedia.com/doku.php/t...shaft_position


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[sportsterdoc]

You already have very good suggestions. I would check for fuel starvation first, either not venting or clogged fuel filter. Then check the coil and after that check the CKP.

[seajay]

Could possibly be a bad carb diaphragm.

[straightshot]

No work done prior to problem.

Great info guys, a good starting point and thanks for the link!

I will report back with the result when known.

[Folkie]

Are you getting any trouble codes?

[straightshot]

My instrument cluster has been changed, po and unknown what he did so no codes show on any readout.

Neighbor mentioned a stator?

[Toejam503]

Stator would cause the battery to go dead. Fuel strainer/filter in petcock first then check the coil. Your fuel cap might not be venting.

[straightshot]

UPDATE: We think it was a loose ground and battery terminal connection. I rode over to the shop with the gas cap loose and no issue and everything has been fine since. Only problem is it's in the upper 40's so maybe not hot enough to rule out coil or other things mentioned. I'll have to wait for Spring I guess to be sure. Thanks all you guys for the responses, much appreciated. Keep the shiny side up!