Both of those figures seem a little too drastic, especially the 500 mile one, which means you could be giving yourself a lot of unnecessary work, maybe every month or so. If the bike is an unknown, then by all means give them a service, once they have been cleaned I wouldn't have thought you would be using it for everyday commuting so there shouldn't be any problem for several years. The best time to do it would be every time you do a top end overhaul, and that would depend on how many miles you pile on it. The last 21 I owned, I rode on the road for 2 years before I done a complete top end, ie pistons, rings etc, then done a further 4 years, mostly on track, and completely ragging the ass off it, using a good quality oil, ( very important ), the same bike is still be using by the present owner with no further work on the motor, though could possibly do with a new set of rings by now,----- wink. wink johnny. So I would say once you have cleaned them, ride it and enjoy it,, for a few years at least.
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Proud Father of , 05 ktm 400exc supermoto 2018 honda crf rx supermoto