xb12 stubles when fan engages

[AtcBueller]

Hi guys. I just bought an xb12r about 3 months ago and its been plagued with a stuble issue at speed and idle. It drives me absolutely nuts. The motor was rebuilt last week at the local harley shop who happen to have a Buell certified tech but they have yet to solve the problem over the last month. I have been able to create the problem by letting it idle until the fan kicks in and it will start sounding sickly but i can pull the fuse for the fan and it instantly clears. Any help is greatly appreciated.

 

[BuellyBagger]

lots of possibilities there. I wonder if its a low voltage issue or other problem from a weak charging system(when the fan draws power the ignition system or fuel system lose proper signal) Or possible a short between the two circuits. Just chuckin out ideas... let us know how it goes

 

[Zeroflat24]

Replace the fan. Thats the easiest thing to start with. If the bike runs fine without the fan fuse, then runs like crap with the fan having power thats where i would start if i were you(i am assuming you dont know how to run a draw or resistance test that is). Also another thing you could try is to pull the fan out and make sure there isnt something causing it to bind and draw too much current.

 

[AtcBueller]

I have access to meters but I don't know how to test the fan or what readings are within the limits. It hasn't thrown a code for the fan but I believe it was giving a faulty o2 reading. Im waiting for a ecmspy cable so I can start diagnostics myself. Im hoping to maybe run a diagnostic with the fan running to locate faulty wiring. How do I check the fan and the output of charging system?

 

[Zeroflat24]

the output of the charging system can be tested the same way you test a car, with the meter on the battery with the bike running. if you leave the meter on the battery terminals while the fan kicks on and the voltage drops a lot you know its an electrical problem and not mechanical.

 

[AtcBueller]

The CEL came on once it started sputtering so I checked the codes using the jumper wire method and it came up with code 13. Faulty o2. I bought the bosch o2 sensor today but won't be able to do the install or check for anything else until next Tuesday. Im not sure if that could be the real culprit but I filled up today and found out I was getting maybe 25 mpg.

 

[AtcBueller]

i got my ecm cable in today and I was watching the volts as the fan engages and it slowly drops from 14 volts to about 12.5 where it eventually stalls. I also noticed that my AFV was at 143 which seems excessive. Any suggestions of where to start on the charging system?

 

[GAXB9R]

I would check all connection and wires going to the fan you may have one grounding out causing an arc of some sort. Which could be causing a larger draw than it would be normally. Look for any damage to the wire insulator craked onnectors. Just a thought. It's the cheapest and easiest first step and only requires your eyes and patience.[cool]

 

[AtcBueller]

I changed my o2 sensor yesterday and checked the wiring to the fan and other connectors the best I could. I cant seem to find anything wrong. The miss and stumble has now started in just about any stage of the ride so I feel this is narrowed down to either bad fuel delivery or spark. The plugs only have about 250 miles since the rebuild so I'll pull those today and see how they look. Thinking maybe a bad coil? i replaced the wires about 1k ago.

 

[AtcBueller]

Turned out the coil was bad and I replaced the voltage regulator just for good measure. Now she is running like a champ! Thanks guys.

 

[uly luigi]

[up]glad you got it figured out