I need you guys expert opinions for my problem. My 2007 fuel injection 1200 sportster has suddenly developed some flatspots at different speeds through all the gears. Under acceleration it will go then stutter and then go again. In top gear it's ok but at a constant speed 80 to 100 km/h it surges. It was running perfect when i bought it 3 weeks ago. I checked the diag and it says none. Your help is appreciated.

 

Fuel filter?

 

I assumed the dealer replaced it when I bought it, was told they gave it a service, has new filter and oil, maybe I should not assume hey?!!

 

bad Fuel?

 

Does it stumble when you roll on the throttle to accelerate but runs ok when back off throttle?

Indicates starving for fuel.

Or

When placing a load on the engine as when accelerating hard it causes the ignition system to miss.

 

Not fuel, fill car and wifes bike at same station - no problem.

Yes
When placing a load on the engine, under acceleration

 

take it back to dealer and have them unservice it

 

How many miles are on the bike? Things to check. Pull the spark plugs. What color are the in side of the plugs? White indicates not enough fuel, dark brown/black to much fuel. Check the air filter. Hold it up to a light source, can you see light through it? Have you washed the bike with a pressure washer?