Q How do I know if my KTM 690 Duke is off its rocker?
I’ve just bought a used KTM 690 Duke only to read some horror stories on forums about rocker arm failures. How can I prevent this happening on my new pride and joy? Leslie Beckett, email
Answered by Daren Butler, KTM technician This problem has been about since the 690 was launched in 2007. What happens is that the pressed pin between the fingers of the rocker arm works itself loose and starts to creep out until it clips its neighbouring rocker arm. When that happens, the pin breaks and its needle roller bearing falls apart.
It won’t clout the piston as the timing isn’t affected and the broken arm means the affected valve stays shut, stopping the engine dead. Not a problem at start-up, but if you don’t catch it immediately those needle rollers can get scattered through the engine so you may need a full strip to clean them out.
It’s easy to take the rocker arms out and inspect them for wear at every valve check service, and if a bike is new to you I’d recommend doing it as a matter of course. The part numbers for the rockers have changed so they can be replaced with suitably modified ones. If your bike is a twin-plug version and starts to run poorly in the mid to high-range, but nothing comes up on the diagnostics, look to replace the plugs as one is probably breaking down.
Don’t panic. Get the rockers checked and you’ll be fine
Have the rocker arms removed and checked for signs of wear