High Speed Thumping

[rhody]

Not trying to change the subject, but check out the cross plane crankshaft on the 09 Yamaha R1, and description of inertial torque, combustion torque, and how the cross plane crank smooths this out.

With all the variables that have been proposed as the cause of high speed thumping so far, would anyone venture to guess whether the engine/shaft drive coupling be smoother using a cross plane crank setup, and if so, would or could this contribute to reducing or eliminating the thump so manyh riders have experienced on shaft drive bikes for the past 20 years ?

As I mentioned in a previous post the other day I would love to hear from someone who has engine/shaft drive design expertise who could shed some light on the issue.

 

[Kasey]

From what I gathered from this thread and the other one these folks have experienced the same issue (or something similar)
SPORT

rbentnail

rhody

fraler

mikep

Anyone else?

You can add me to the 'thump thump' list. I did a forum search for 'steering head bearings' and was very happy to read this thread.

'03 w 116K km. I replaced my worn front RoadSmart with the same before I took off on a trip last month. It felt like I was riding on washboard from the get-go and is felt from 70 - 115 kmph. I fiddled with tire pressure and re-adjusted my camping gear load several times and there was no difference. While at a rally in Omak WA someone noticed that the front wheel weights had fallen off - ah ha! I thought - there's the answer. I took it into a dealer there to have the tire rebalanced and nothing changed.

When I arrived back home with 3500 km on the tire my dealer changed it out no charge for a new one as I had said it must be a defective tire. To my chagrin the new thumped as badly as the old one. I took a day ride over different types of pavement then went back to the dealer where a couple of techs took it out for a ride and each said they noticed "a little something". I think that in order to try and satisfy my complaint they played with the front and rear suspension settings but their adjustments made no difference. I'm not dissing them for feeling nothing wrong as no one knows the bike's feel better than the owner. We did discuss possible worn steering head bearings or a fork oil change but reached no firm conclusion as to the cause. (Having just dropped a tidy sum for a camchain, et al, replacement and a six week wait for the job to be finished I am not too anxious for those particular hands to get back into my bike's innards.)

I have never felt the thump before - so why did it show up after a new tire install? Is the (possible) onset of worn bearings just coincidental? Thanks to what I've read here I'll take a ride this afternoon and pay particular attention to the speed/rpm suggestions.

Kasey

 

[Kirrilian]

Well, I have been through at least 3 sets of tires since the last time I looked at this post and I am still getting this thumping. I have pretty much given up on it since it doesn't seem like anything is going to blow up and no one can seem to figure it out, including me.

 

[Kasey]

Well, I have been through at least 3 sets of tires since the last time I looked at this post and I am still getting this thumping. I have pretty much given up on it since it doesn't seem like anything is going to blow up and no one can seem to figure it out, including me.

Bump. First ride the other day but I didn't go far - I had forgotten just how bad the thumping is and it was Awful. Will take it out again soon and follow the routine suggested by Rhody.

I guess no one else has found a solution?

Kasey

 

[Kirrilian]

Still having it here and I've been through several sets of tires since. I have checked pretty much everything that folks have suggested on this thread too. I think it is inherent in the drive or maybe there were some that had a small defect that none of the other ones have. So, yes, AFAIK there isn't a solution to this.

Glen

 

[Fred W]

Have you guys ruled out drive shaft un-balance?