ANY QUESTION ANSWERED
If we don’t know the answer, we’ll find the person who does
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.