Q How do I know if my KTM 690 Duke is off its rocker?

Motorcycle News (UK) - - Garage -

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

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