Installed 255 cams last week. Only other mods are Stage 1 air cleaner, Rush slip-ons, and SEPST w/Smart Tune software.

The install went fine; everything lined up perfectly to my eyes. Went through the top and reused stock pushrods. Engine fired right up and sounded good with the stage 1 base map still loaded into the ECM. No weird noises. Loaded in the 103 Stage 2 base map from the SEPST software and adjusted the displacement down to correct for the 96".

The bike still sounded great but on my test rides I'm getting a pretty bad stumble when the engine is lugged down a bit in each gear. It's not there all the time, and the bike runs fantastic and mid-upper RPM ranges...really smooth. I only noticed a very slight hesitation at cruising speeds once or twice.

I'm finally learning the Smart Tune feature, but as of right now I haven't made any changes to the Stage 2 base map except for displacement.

Would you guys expect this stumble to tune out, or is there a chance that I'm off one tooth or something? Like I said, the bike runs like a champ once you get into the throttle. It's just at low RPM, mainly when the engine is lugged, that I get the stumble.

If it should tune out, will Smart Tune take care of it, or am I going to need to visit a dyno?

Hope someone can put my mind at ease!

 

My money is on the tune; sounds too rich at low rpm. Like the A/F adjustment on a carbed engine.

Could also be too lean, per Sickbagger's experience. Hard to say when you can't hear/feel the stumble; if it is "bogging" down or spitting/coughing. I am not a tuner but I think you will have to have the bike on the dyno to make the correction unless you just start adding/taking away fuel at off idle and low rpms and see what happens. You can collect data with the SEST but it doesn't have the VTune feature that the TTS has.

 

I had the same thing with my PCV and AT it fixed it but it added fuel not took it away. Be interesting to see what your AT will do. Took me several rides exercising the bike at this very low RPM most take off from a stop a little higher RPM range. Mine runs great now!

 

Thanks for the replies. Gives me a little relief now that I know I probably have everything together right. Any other thoughts? Lots of people installing 255 cams these days, but I don't see anyone reporting on what they are doing to tune the bike after the fact. Keeping same map, using a different base map, smart/auto tune, dyno?

 

You need to change the map you are using.

Find a base map that uses the 255 cams and start over.

 

That's where I'm at right now. Loaded the 103 Stage 2 map and changed the displacement to 99.1 on a recommendation to keep it running a tad rich. Still have the bad stumble, but should the Smart Tune take care of that now that I have the right map? Just trying to rule out an installation error (e.g. off a tooth) before I waste any more time with Smart Tune.

 

I just installed the 255's on my 09 Ultra with PC V, I'm running into the same problem at cruise speed, between 65 and 70 mph. My "stumble" last less than a second and only seems to happen 2 or 3 time per tank of fuel. Apparently your situation is not unique and I doubt it has anything to do with the way you installed your cam. My gut tells me it's has something to do with the TPS setting in my map, probably a little more fuel at this position would help, I just don't have an idea what the TPS value is when I experience my "stumble"

 

There are multiple stage 2 maps to choose from so make sure you use one that specifically identifies 255 cams. The timing tables are way different than those with stock cams.

 

After installing my 255's mine was running rich which surprised me. I would have expected lean. (I have the same tuner as you) Before the install I had already dyno tuned the bike then installed the 255's myself. It didnt really stumble much but after a good dyno tune, all is well. Im betting a competent tuner can get you going. From your description, I think the install is fine and just needs tuning. Let us know.

 

There is only one map for the 255 cams included with the Super Tuner software. It's the 103 Stage 2 map, but the displacement can be adjusted. That's the one I have loaded right now. Maybe some smart tune runs will fix this problem.