Love my ST3S, but it has an annoying habit of occasionally ‘coughing’ back through one of the valves into the airbox. (Can be seen - rear cylinder, soot around the intake). It makes the bike a pain in traffic and at low speeds/small throttle openings. Only seems to happen when engine warm/hot, not from cold. Any ideas on how to fix it/what it might be?
This section of the forum is a bit of a desert as far as viewers go, you may be better off reposting this in the Techinical Help section or perhaps @El Toro could move it for you
Bud is going to do a 2 year service including valve clearance and TPS/balancing. We suspected it to be this, as how else could gas come back through the intake? (Valve clearance too tight). Also possibly the fuel hose perished inside the tank causing low fuel pressure at times? Hopefully going over it should solve??
