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Motorcycle News (UK) - - Garage -

Q I’m keen to stop my KTM run­ning lean

I’m the third owner of a KTM Duke 690 and I think the orig­i­nal owner was a bit nuts as he fit­ted it with a de-cat­ted full Akrapovic ex­haust, Power Parts air­box and a race camshaft. When I ac­cel­er­ate hard from a stand­still to the red­line through the first two gears it’s fine. How­ever, when I put it into third gear it car­ries on pulling then stut­ters. The same ef­fect can be achieved from a rolling start where it hap­pens later in the rev range or in fourth gear. Could the bike be run­ning lean? Wayne2009, MCN Fo­rum

AAn­swered by Daren But­ler, Jim Aim Rac­ing The mix­ture on your model tends to be lean, and those changes will make it worse. Al­though it seems to be speed-re­lated, you use less throt­tle in the lower gears as the bike ac­cel­er­ates through them quickly so the en­gine isn’t loaded as much. When Dyno­jet an­a­lysed the map­ping on the Duke 690 they ad­vised adding 20% more fuel when be­low 4000rpm in a high gear, so you need to get it booked in to a good dyno cen­tre with some di­ag­nos­tic kit. But you can start by go­ing through the bike’s own ini­tial­is­ing pro­ce­dure, then take it for a quick test ride.

KTMS have in­tel­li­gent ECUS which mon­i­tor the air pres­sure and tem­per­a­ture then ad­just the fu­elling. Start it with­out any throt­tle, so the but­ter­flies are at the base set­ting, then let it idle. On a road bike this takes 15 min­utes from cold, or 10 min­utes from a warmed up en­gine. The off-road and com­pe­ti­tion mod­els do this in five min­utes, partly be­cause of over­heat­ing is­sues. It’s good prac­tice to do this on any KTM, es­pe­cially if you have put the bike away at the end of sum­mer and then go out on a crisp, dry win­ter’s day.

Get your­self down to a de­cent dyno cen­tre to sort that fu­elling

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