Hi to all, I new on this forum and I have some problems with my single 660 big bore yamaha mt 03 2006 without O2 sensor. I have on it akrapovic exhaust.
First problem: with db killers on idle speed is very unstable 1500-1800rpm. Without db killers is stable at ~1500rpm. Why? Second and big problem is engine die when I try to move with 1st gear and I accelerate a little bit, is like fuel stop. Third problem is if my bike is in neutral position and I accelerate at 3000rpm when I try to give a little bit gas my engine go down at 2900~rpm and with a little bit gas start to go up at 4000-4500rpm. All of this because exhaust is Akrapovic? Or I need kev mod to install or power commander?
Thanks Guys.

how cleans is the air filter?..standard or aftermarket?..whats the plug like?..snorkel removed?..all the free mods and checks made/done?...

Air filter is hifiltro, airbox is standard, no modification, everything is stoc only exhausts are akrapovic. I tryed with no airfilter inside on neutral and same thing happend. Plug is new ngk iridium, same with airfiler, is new, oil motul 7100 10w40 (200km).
This is my bike: 21.000km

if you search the forum all the tips etc are there for you ... http://i144.photobucket.com/albums/r200/xt660/SS-1.gif

I would check side-stand switch, clutch switch and as first step TPS.

Side stand switch works very well. When I bought motorcycle clutch switch was damaged and I repaired it, it is working very well now and please can you explain to me what to do with this TPS? Thanks, really apreciate.