Recently my lovely bike has developed a little habit of farting/phutting into its air box. Typically this will occur at low revs, just off tick-over, you'll be pulling away from a junction or just putting the the power back on coming out of a bend, then fart and away! Not every time, but enough to cause concern/ irritation! Now, Google/internet wisdom suggests this is probably a result of running too lean. I would like to understand how lean running would cause this? I would have suspected this would be the result of poor timing or valve seating? I have Gunson on order and thanks to ChrisW access to the ecu trimmer. Any help appreciated!
My 998 did this when it was new and it was due to running too lean, I only had stock exhausts then and it was as it came out of the factory. I had some major backfires\explosions out of the airbox on slowing down particularly for junctions and for give way signs. When I took it to Sigma performance for a service they identified it as the problem. I got round it coincidentally by buying some Termignoni's which came with a new ECU. But when it was running lean it really did seriously backfire to the point where I could feel it blowing through the rubber seal under the tank. Mine was purely a weak mixture and a Ducati dealer or similar should be able to sort it out.
Mine used to do it and only after reading this I realise it doesn't any more but I now always run it on super unleaded whereas I used to just use normal.
Thanks, I'll try some injector cleaner and some posh, non-Asda petrol... I'm still interested how a weak mixture can cause this? I'd have thought any farting or backfiring into the air box would be due to compression leakage of some sort? Cheers
I'm not sure of the science but a lean mixture will certainly do this. After I had my 916 gasflowed (valves etc. were perfectly setup) on first startup it was doing this massively until I richened the mixture. Running it with the airbox off there were flames blowing out of the intakes - not good if you have an over the intake filter or plastic fuel tank... Co readings were around 1.5 - 2% but once dialled up to 5% it ran beautifully.
My 916 did this last year.Just a nats off closed throttle,pulling away or poottling through town,trying to look cool,well you know.I had a small amount of play in the throttle linkage,so swopped a newer one,set the TPS and it hasnt done it since.
5% on the gauge, with the gauge set at 2% in fresh air before starting. Bike was then mapped on dyno etc. and baseline was good when measured by AFR.
