When my 630 was new it surged and hesitated at 4500rpm while just barley on the throttle (like they all do i hear). Then i did the power up mod and it was still surging a bit, but not enough to really bug me. Then i put my fmf exhaust and JD tuner on and it surged, popped, hesitated WAY worse! I played with the JD tuner (final settings 3, 7, 6/7, 3/4, 5, 6) and the hesitation is better than it has ever been. Almost gone, but still there. I'm happy with the ride, if i have my ear plugs in i don't even notice the blips and burps at 4500rpm. its hardly there. What i'm wondering is...does anyone actually know what the issue is? Any engine pro's out there? Any EFI guru's? The JD tuner comes programed a little bit richer than stock in 1/8-1/4 throttle range. but this richer setting made my bike surge more? but i modified my bike to flow way better? U would think i would need to be richer than stock? but in the end i had to go back to the stock setting in the GREEN (1/8-1/4 throttle) range to get rid of the surge? internet research says surging is usually a LEAN fuel mixture? not on my bike. i had to make it lean to get rid of the issue?
Try an iridium plug and see if that helps. My bike just has the lab removed, PU kit, and twin arrows with new ecu.
ya, i will have to try that iridium plug. if this is the cause, i am amazed a spark plug can create surging at a very specific RPM only.
All motors have an rpm spot where they just don't wanna run right -- torque drops off briefly. I have forgotten the details from my college days as to exactly why that is. But intake and exhaust manifolds/headers are usually designed to work best at that specific rpm in order to help the motor get over it. Don't know if that's the 630's weak-spot rpm or not, but it might be.
Same here with my SM 630. With the stock pipes and the air box opened up, I had the Green setting at 2/3. Now I've got a full Leo and my Green setting is at 3. The factory settings must be overly rich just off idle. My bike pulled noticeably stronger off the line using 1/8 to 1/4 throttle once I leaned it out a little.
