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high speed oscillating rumble on pavement?

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Commuted to work on my 17 500 EXC-F today for the first time, about 25 miles of mixed highway and secondary. The bike has tons of power even stock but it develops this, for lack of a better word "oscillation" or intermittent rumble, about one a second, worse as speed increased above 55 or 60, it's not the tires, but it gets to be filling shaking at over 70...

is it engine harmonics? suspension interacting with knobbies to create a sine wave type pattern? I remember this before in some dual sports I've had, but forget if I ever fixed it... Help me,  oh wrenching gurus!

(Not sure if I should've asked this in KTM or here, more of a general question I guess)

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I had a KTM 560SMR (on 17" street tires) street registered that had chain slap (to simplify- a chucking/oscillation feeling) at cruising speeds above 50mph.. Went away upon acceleration or decelerating.. My conclusion was to upgrade to a coush drive rear hub... Never got around to it before I regretfully sold the BEAST a few years after purchased. Perhaps you re feeling this as well?

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19 hours ago, gman255 said:

I had a KTM 560SMR (on 17" street tires) street registered that had chain slap (to simplify- a chucking/oscillation feeling) at cruising speeds above 50mph.. Went away upon acceleration or decelerating.. My conclusion was to upgrade to a coush drive rear hub... Never got around to it before I regretfully sold the BEAST a few years after purchased. Perhaps you re feeling this as well?

I got the wheels balanced today and will put them on in a few hours and try riding again. Softening up the suspension helped a bit. If chain slap was a function of chain tension/oscillation could you change that by changing the chain slack? You know, just like tuning a piano?

Edited by kayakingsteve

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Got the newly balanced wheels on and no more high speed oscillation, the guy at the shop today told me that KTM doesn't balance the wheels from the factory in spite of the bead locks because they don't anticipate people will be doing lots of highway riding... and the dealership... well, it's a typical dealership, they are so busy servicing whiny suburbanites' jet-ski's that daily riders are not their main customers. . Problem is fixed though!!! Was a joy to ride tonight finally. Like a rocket! I'd say in stock configuration the 500 could give my F800GS a run for its money from 0-80.

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