Headshake on loose gravel

Not sure if this is the right place to post, but I need some help sorting out a quite severe headshake.

Bought the bike last week, no headshake. Fork seals were toast, so I had them replaced and now she like to wobble on loose gravel from 80-100km or so. I don't think the bike did this before the fork seals were replaced.

Also put new Mitas C16/17 tires on today and now it seems a little worse.

When I had this issue on my KLR, I lowered the front end a half inch and that seemed to work. Maybe my front end was lower before the new fork seals and fluid? Before, you could just blip the throttle and stop the shaking, now I have to stand on the pegs to keep it upright.

Any one had this and fixed it?

I've lowered mine (raised the forks thru the triples too), and haven't experienced that with those skins. I know when I had the 606 front skin on, it didn't like loose gravel, but it didn't give me headshake in that sense. Headshake in the sens of wtf is wrong with this tire...??

SheWolf wrote:

I've lowered mine (raised the forks thru the triples too), and haven't experienced that with those skins. I know when I had the 606 front skin on, it didn't like loose gravel, but it didn't give me headshake in that sense. Headshake in the sens of wtf is wrong with this tire...??

I don't think it's the tires, because it was like this with the baldish stock tires yesterday too. Honestly, not sure what people call "headshake", but the front end starts to wobble first and then the rest of the bike will wobble like 6 inches side to side if I let it...

You might ask what fork oil the shop used. Factory is super thin stuff.

Sarah

I'd double-check:

Fork oil level.
Fork tube height (which adjusts ride height of the front end).
Steering head bearing tension.
Tire pressures.

As Sarah brought up, pancake syrup in the forks instead of the recommended oil could cause problems, too.
The recommended oil is not hard-to-find stuff, either, so hopefully the correct stuff is in there. :)

+1 on checking tire pressure. For me, gravel is like riding on marbles unless I drop the pressure to 18 rear and 14 front. I normally run 26/22 for pavement.

+ 1 on tire pressure. My bike moves all over the place on gravel if my tires have to much air in them. I find that anything under 20psi is best. Preferably, 15-17.

Thanks guys What is the recommended fork oil? I assume that the Yahama stealership would have put the recommended oil in...but you know what happens when you assume. The only reason I took it there is because the the guy I bought it off of paid for the seals to be replaced.

But I'm guessing the consensus is right: tire pressure. (I would go an check, but we have a torrential downpour going on.) I was running the "recommended" 18/25, which is already quite a bit less then I'm used to on the KLR, but I think the much lighter bike, much knobbier tire combo is making her squirm on the loose stuff. Now that I think of it, the bike handled the gravel better loaded up. than with just my 150lb carcass. Problem is my commute is 4 miles loose gravel, 15 miles pavement each way, so airing up and down constantly is not going to work out. Can anyone recommend a good combo pressure for the Mitas tires? Trying not to wear these new shoes out too fast, but I'd rather not crash either...

I don't think you're describing "Headshake", which is usually described by the handlebars shaking so violently you can lose your grip (Imagine handlebars being mounted to a paint can shaker).

Gravel roads are very difficult to gauge set-up on. Not sure I'd use it as a baseline for set-up.

Outside change, but you might as well look at wheel balance as well. The front is relatively easy to check and solve with a few wraps of solder.

I live by my fork bleeders on my CRF. Once the forks heat-up they don't react to light chop/washboard nearly as well. If it's warm and you are in bumps a lot, fork-bleeders can help.

The WR, with lighter weight forks actually work better for me (at 210 lbs) once they warm up.

Good luck !

Like most things we all have different "terminology"
Headshake to me fits just fine for what is being described--a wiggle in the bars due to sand or gravel surface--me I just let it shake and steer with power.
What you have described is a "tank slapper" which to me is much more violent--been there done that don't need to revisit and it has been 40 years. Headshake is just a rythmic motion that I encounter on just about every ride in loose dirt, sand or gravel.

X-Racer wrote:

I don't think you're describing "Headshake", which is usually described by the handlebars shaking so violently you can lose your grip (Imagine handlebars being mounted to a paint can shaker).

Gravel roads are very difficult to gauge set-up on. Not sure I'd use it as a baseline for set-up.

Outside change, but you might as well look at wheel balance as well. The front is relatively easy to check and solve with a few wraps of solder.

I live by my fork bleeders on my CRF. Once the forks heat-up they don't react to light chop/washboard nearly as well. If it's warm and you are in bumps a lot, fork-bleeders can help.

The WR, with lighter weight forks actually work better for me (at 210 lbs) once they warm up.

Good luck !

Pressure I ran on loose gravel/offroad on the Mitas was 14 front 16 rear, no problems.

Akasy wrote:

Headshake to me fits just fine for what is being described--a wiggle in the bars due to sand or gravel surface--me I just let it shake and steer with power.

What you have described is a "tank slapper" which to me is much more violent--been there done that don't need to revisit and it has been 40 years. Headshake is just a rythmic motion that I encounter on just about every ride in loose dirt, sand or gravel.

Humpfh.... I just call what you described as, "a wiggle in the bars due to sand or gravel surface"

Yes... The much more violent "Tank Slapper" is when you are going lock-to-lock swapping ends over big whoops. It is called that because your bars slap the tank (or your legs between the bars and the tank) < Like" Duh as my daughter would say >

What I refer to "Headshake" is not rhythmic at all and on a large HP sportbike coming hard out of a turn, it is violent. Obviously it can happen in the dirt as well but in my experience is usually on short-spaced bumps and in staccato fashion.

Some however may slap theirs harder than others. * LOL *

All-in-all I s'pose it's a simple matter of frequency and amplitude.

If what is being described as headshake from looseness on gravel or sand, then my head is shaking from the start to the end of most rides (if the front wheel is on the ground).

I'd be hard to convince that lowering the forks will take that out. I would tent to think it would amplify the sensation. I'm thinking I would sit back and roll the throttle on and try to commit the front end more, (rather than to let it float).

Thinking again... I probably don't think about it. ...but now I am. I better start paying attention ! * laugh *

Look here about 5 seconds into the clip: THIS is headshake. Albeit on a scooter.

https://www.youtube.com/watch?v=6iPx8Xgl9cA

X-Racer wrote:

I just call what you described as, "a wiggle in the bars due to sand or gravel surface" The much more violent "Tank Slapper" is when you are going lock-to-lock swapping ends over big whoops. It is called that because your bars slap the tank (or your legs between the bars and the tank) < Like" Duh as my daughter would say >

You guys are hilarious. Anyways IMO, it's the same thing as what you call a "tank-slapper", just the preliminary stages and easier to get out of. A simple matter of frequency and amplitude, as some would say... Used to happen to me on my CBR1000 Hurricane when you hit tar strips going too fast (220km/h +) around a sweeping corner. I used to deal with it by praying, staying loose, and goosing it. On my old Magna (which had a bent frame) I left black semicircles down the road for a quarter mile doing the same thing.

Personally, I think it happens when the front end gets too light while catching uneven traction, as scootching up works, as does standing up (preventing your body from amplifying the wiggle.)

Yep, on the street "sit back and roll on the throttle"--exactly what I do when she starts to shake.
In the dirt weight on the pegs--I don't stand all the way up--just up a little and my rear moved back and throtte up--- if she starts to shake.

I don't do high horsepower sport bikes but I can report that at Daytona those guys are flying on the banking and from close up in the infield you can see a whole lot of flex and movement in the frames

Tar strips are ugly on pretty much any motorbike, knobbies included!

You can read all about the forks starting on about page 150 of the service manual, it calls for Suspension Oil 01. The local dealer had no clue, when the parts guy looked it up he said it was pricey stuff and had no idea how long it would take to get it in. I used Honda/Showa SS7 which is a 5 wt. fluid, thin stuff. As for the ride, feels about like it did from the factory, near as I can tell.

Sarah

Yamaha's Kayaba 01 oil is ordered from the same warehouses the Yamaha OEM parts come from.
Funny, because this stuff has been around since cartridge forks first came out on Yamaha YZ motocross bikes in 1988.

Last I bought a can (and it comes in a real metal can), it was about $22 for a liter.

greer wrote:

You can read all about the forks starting on about page 150 of the service manual...

Sarah

Thanks Sarah. Is there as .pdf of this service manual kickin around, by chance?

Yep there is. Right here.

SheWolf wrote:

Yep there is. Right here.

Thanks!

I just put a set of the C16/17's on last weekend. Ran about 150 km on them thru lots of sticky clay and fast gravel roads with no problems. No rim locks.

Torco 5wt level at 110mm you can get that at any shop. This is what Travis at GoRace uses when you send him your forks...


If your bike was fine before they worked on it I would ask them what they used and how much...
I only say this cuz I could see how it was played out from my yrs as a tech in a shop..


Hey what wt oil should I use in the WR???
Look in the book!
I can't find it..
Put in 10wt or 15wt the guy riding it will never know they don't really ride them off road anyways..
Ok 15 it is...

Not say`n this happen to you but it does happen a lot... Also if you gave them the bike and not just the forks off the bike the tech may of put a bit more air in your front tire. Some that don't ride off road will air up a tire for the road and not think about doing it...

What you describe is normal, IMO, on loose gravel at higher speeds. I've gotten to the point of actually enjoying the sensation of sliding around like that.

Does it do it on asphalt? If not, then there you go.

MeefZah wrote:

What you describe is normal, IMO, on loose gravel at higher speeds. I've gotten to the point of actually enjoying the sensation of sliding around like that.

Does it do it on asphalt? If not, then there you go.

Yeah, I'm starting to think this is normal for a light(er) bike like this and it's just the type of gravel I'm riding. Suspension/tire pressure doesn't seem to change much. On the road it's smooth as silk.