640 Supermoto vibration

Hi ,

A friend og mine just bought a new 640 (LC4). He is complaining about the amount of vibration he feels through the saddle , after a 30 mile ride his "groin area" was completely numb !. The vibration increases with engine speed. Can anyone tell me if this is normal for the LC4 based models ?

Thanks .

Jerry (on behalf of "numbnuts" :)

I've complained about the same with my LC4 - to no avail. Some recommendations have included softer seat foam (see earlier posts) and standing up more. Don't know if I've finally broken the foam in or what, but it doesn't bother me as much now as 16 months ago when the bike was new off the floor. I probably don't ride it the same, either, as then and both get up on the pegs and vary the RPM's more (gassing it).

Tell what's-his-nuts "Welcome to The Monkey Butt Club"! :)


'98 RXC 620

Thanks KatoomRXC , your answer kind of assures him that its not mechanical trouble causing it. The dealer told him that its normal , but seeing as he´s owned and ridden all kinds of bikes from old British singles and twins to drag race Harleys and not experienced these kind of nut-numbing vibes before , he needed the opinion of other owners. Do you have any idea what causes the vibration ?

By the way , he has been welcomed to the Monkey-butt Club and will probably be cruising this site himself soon. Thanks again.


No idea why, really. I'd just be guessing. My previous bike was an XL600R - affectionately known as 'The Couch'. It didn't have anything resembling my RXC's vibration.

If pressed, I'd guess it's related to higher quality, more rigid handlebars, combined with a shorter stroke. The Honda had dampening weights in the handlebar ends, too, which no doubt made some difference.

Here's 'The New KTM Effect' katoom-baboon.jpg


'98 RXC 620

[This message has been edited by KatoomRXC (edited 07-18-2001).]

[This message has been edited by KatoomRXC (edited 07-18-2001).]

This is Numb Nuts in person,thanx Katoom for welcoming me to the MBC .Is there a membership fee ? and if so, is one of those "blow up cushions" with a hole in the middle included in the fee ?

Thanx also for the reassuring reply , I really thought something was wrong and the dealer was just B-S ing me.

Also ,Jerry ,Thanx a Million ...

Katoom RXC ,

Love the picture , gotta get me one of those LC4´s :)

Numb nuts , as always , you´re welcome.


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