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The high speed oscillation or rumble phenomenon, can it be fixed?

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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!

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40 minutes ago, TriumphTriple said:

Mine does the same thing. Wheels need to be balanced. 

Has anyone you know fixed it with balancing the wheels? I sure want to get it fixed because the bike is basically un-rideable for longer distances over 60 mph.

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Don't bother trying to trouble shoot until the wheels are balanced.  Rim locks are very heavy and the wheels are the polar opposite of balanced the way the bike comes. It will take several ounces of lead to balance them.   

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one of my biggest dislikes about offroad wheels. the dang locks are next to the stem , that sux.. I thought there was a kit to re-locate stem and balance . anyone have an idea ? or a product ?

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There is often a dot on the tire to show which side of the tire is heavier, to help balance the tire better.  I don't remember if the dot is supposed to go next to or opposite the rim lock, but google can help.  I just used MSR stick-on weights and they've been stuck to my rims since I got the bike new in december of 2013 if I remember  the date correctly. 

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12 minutes ago, sirthumpalot said:

There is often a dot on the tire to show which side of the tire is heavier, to help balance the tire better.  I don't remember if the dot is supposed to go next to or opposite the rim lock, but google can help.  I just used MSR stick-on weights and they've been stuck to my rims since I got the bike new in december of 2013 if I remember  the date correctly. 

I'm pulling the wheels off tonight and going to swing by the shop tomorrow and have them balance them, since I got the bike literally a day ago that shouldn't be an issue.  I put bead locks on wheels before but nothing fast enough or light enough that the oscillation from imbalance was this noticeable. even with my helmet strapped tight it was still shaking in and out of my field of view if I sat flush on the seat at 70 or more.

That said I still couldn't resist opening it up on the backroads going home today and just kind of crouched a bit over the seat. :)

Airboss: I am no master mechanic but with a drill and good sanding and/or a dremel to polish I just drilled my rim before to put a bead lock in, so it can't be more complicated than that to relocate one.

Edited by kayakingsteve

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The Dot is the lightest part of the tire, few manufacturers use the dot anymore. so if the dot is there, should go with the rim lock.

 

IMO, no dealer can balance tires to my satisfaction, they do okay, but I'll spend 20 or 30 minutes balancing a tire. Those auto mated machines get close, but still not as good as a manual static balance.

Edited by Spud786

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On 4/20/2017 at 1:13 PM, sirthumpalot said:

Don't bother trying to trouble shoot until the wheels are balanced.  Rim locks are very heavy and the wheels are the polar opposite of balanced the way the bike comes. It will take several ounces of lead to balance them.   

Agreed... I just balanced a new set of knobbies and was blown away by how much lead they clamped onto three spokes at one end. Night and day difference in ride above 45mph.

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9 hours ago, LS1Steve said:

Agreed... I just balanced a new set of knobbies and was blown away by how much lead they clamped onto three spokes at one end. Night and day difference in ride above 45mph.

You guys were all right. They balanced mine at the shop today, got them on at home and now from 0-90 I've noticed no oscillation... thing feels like a rocket in stock config. Has a false neutral somewhere in there around 4'th but most bikes have that somewhere and you just get used to it. The shop guy thought I was crazy when I told him I planned on commuting on knobbies on that thing, but I've done it for years and love it. He said KTM doesn't balance them from the factory even with the bead locks, that they don't expect them to be on highway much and the poor guys at the dealership look like they are being worked to death so doubt they think about it when they prep a bike for sale.

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had my 500 and the Dunlop  AT81's out on the frwy for a 5 mile section of yesterdays ride and as noted it had lots of shimmy and shake from the in-balanced moto tires. obviously they are not DOT and I don't give a flock cause we don't do much road time. if I had to go any faster than 70 or further than 10 miles this bike would have street wheels for the highway,.

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I swapped rubber on my '17 500 EXC after the initial break in ride and checked the factory set up prior and the rear TK80 would've required 5 1/2 ounces to balance and the front 3 1/2 ounces. I drilled another hole in the wheels 180* from the original rim lock and installed 2 Motion Pro nylon rim locks on each wheel and with Michelin UHD tubes the rear Kenda Trackmaster required only 1 ounce to balance and the front Pirelli Scorpion Pro required 1 1/4 ounces. Smooth as silk now.

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