I've got a 2005 KTM 625 SMC. The carb has been dipped and cleaned and jetted per jd tuning. It was supposed to have worked well with that combination before. For the past few months, I've had an issue with the bike cutting out very momentarily then back to normal. It would also backfire and spit flames out the exhaust pretty bad on decel. It got so that it was really bad and I thought it was jetting. I tried tons of different jet combos and nothing helped so I put it back to JD's recommendation. I pulled the spark plug and it was black and smelled like gas. I put a new plug in the boot, held it against the head, and the spark was weak. I pulled the coil, cleaned the ground, put it back together, and it ran great. That lasted for about 100 miles and it started again so I replaced the coil and spark boot. That cleared it up for a few more miles and then the issue came back. It doesn't do it as badly or as often, but it's terribly annoying and I'm sure it's not good for the engine either. Does anyone have any ideas on what I could check or what would be causing this? I'm really considering offloading it and cutting my losses if I can't figure it out; its been a nightmare. Thanks. Edit for extra info: Forgot to mention in the original post that the hiccup only happens at steady speed/steady throttle, and on decel with some gas applied. Full throttle seems to be fine. It doesn't do it steady either, it's very intermittent and sometimes happens very often, and other times it might be a few minutes before it does it.