I just bought a 03 Roadking Classic EFI 17000mi. Stock Air box, Vance and Hines basic slip ons. Bike starts up fine. Plugs a little on the white side. Problem is, at low speed cruise 0% to 10% throttle or and thing under 35 mph, no load, the bike seems to surge or sputter as if it is starving for fuel or spark. If it is under a load its fine, cruising speed its okay. Also seems like idle is spratic. Runs up the RPM okay. Any ideas? This is my first Harley and I love the bike. Thanks in advance for your input. Im getting ready to do a SE/AC and a stage 1 download in hopes that it will help the issue.

Any iniput would be great.
zzmellio

 

First, I would check the primary chain adjustment. If it is loose, the bike will surge at low speed. My '06 Heritage did it new. A quick trip to the dealer and a little adjustment and the problem was gone. Also, if you have a performance after market exhaust without a high flow air cleaner and stage one download, you have release the back pressure on the cylinders affecting your off idle torque. Doing the AC and download will bring the off idle torque back by increasing the firing pressure off idle.
Let us know what you find, and congratulations on your new ride!

 

Like so many Harleys you have a 2000 RPM flat (lean) spot. Your AFR (air fuel ratio) needs to be adjusted for that rpm range. In other words your EFI is set at different AFR's over the RPM range. Less at lower rpm's where you don't need that much fuel and more at the higher rpm's and when you have a load. I don't think the Stage 1 download will fix it but you can try it if you want. Usually it will take a PCIII or SERT to adjust your AFR. You have absolutely no adjustment on a stock bike or with the download.

 

Well I went ahead and did the Stage 1 download and a SE/AC. It does run better but it did not eleviate the problem altogether. I am ordering a PCIIIusb and will give it a try. I am wondering now if the TPS is out of wack giving false signals to the ECU? The bike shows no codes of any kind. I know that electonics can be intermittant and am wondering if the TPS is on the verge of bing out of compliance with its base settings. Again thanks for all of your input.

 

Are the symtom I am having common among others with EFI? I know the all the bike a lean from the factory for EPA regs but come on. It seems that if you get a better AFR the the bike will run cooler and it wont be in the shop getting fixed. How many repairs do you think are do to the fact the the engines are running to lean and the excessive heat is the cause of failure?

 

Well I got the PCIIIUSB a few day ago and have installed it. I downloaded the can map M807-010. It does run better, but not to my liking. I moded the map some, I set the throttle position and the put the map in advance mode to see more detaied RPM ramge. The bike idles between 950 to 1150 RPM. I guess that is normal? At zero % throttle and 1000RPM I went form 0 to 5. From 1250RPM to 2500 RPM @ zero throttle I went to 3. The bike now runs better at slow speeds, 10 to 15 MPH. I took your advice and helped out the flat spot in the 2k rpm range. Im still think that the bike idles a little choppy but it sounds a whole lot better. Decel pop is 90% better than before. The bike seems to pull harder and runs like it is'nt laboring as before.