MILEAGE: 39755km or 24702mi

Date: 17th September 2017

With nearly 40000km or 24800mi I did a big maintenance check to Чернотa. I was really curious about it due to the sparks plugs. They have been used for the double recommended mileage!

Чернотa jacked up and ready for opening up …

its chest. The …

camshaft looks nice (except that axial bright stripe on the lower cam which is there since I own the bike – but there are no surface irregularities  – so no worrys).

​Besides a few fine auto-decompression-chatter-marks on the exhaust rocker arm reel the rocker arms (probably the weakest point of the older KTM 690tys) are fine after such a long distance. The valve clearance was with: EL:0,12mm, ER: 0,11mm, IL: 0,11 and IR: 0,11mm perfect within the specs.

Despite 20000km or 12400mi and the usage of an open air box cover the air filter …

looks surprisingly clean. Whatever! A new one was installed. 

The oil magnet and both oil sieves also looked really nice. No obvious big metal parts or similar after 12200km or 7580mi since last oil/filter change. And now to the most interesting part:

The spark plugs: As a former mechanic coming from the car sector I know that similar spark plugs in a car engine are often in use for 60000km or 37300mi or more. So I made the experiment and doubled KTM´s recommended maintenance interval from 20000km or 12500mi to 40000km or 25000mi. As expected the inner (center) spark plug looks fine after that distance compared to a new one. The color of the electrode is 690 typical grey/white and there is no obvious wear. There´s also no crack or damage at the ceramic isolator around the center electrode visible.

Side (outer) spark plug: asides the color (a bit darker here due to less heat stress) it´s the same here. There is no damage or obvious wear visible.

My conclusion: Doubling the spark plug maintenance interval on the KTM 690 engine is possible*.​

* imitation at your own risk  ^_^)

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