Jolting through the bars

[darius]

Hey guys.

I've had my '07 for just over a week now. Rides perfect on smooth roads.

The problem is on the slightest bumps, even riding over a white line, the front gets jolted rather harshly. It's like if I hit the smallest thing at the slightest angle with the front wheel, I get knocked about right up through the bars.

I understand the fork is completely non-adjustable. Compressing the fork I don't feel any issues there. The rear shock is set to '3', normal for preload.

The tires are still stock @ 3k miles, BT-020. 33-36 psi in the tires per the swing arm label.

I've ordered a set of 'PIRELLI Diablo Supersport Street' from CG, thinking that the stock tires are old and hardened up.

Is there anything you guys would recommend checking? Thx!

 

[mikw73]

Just a guess, but the head bearings may be loose. Kind of a known/ongoing issue on a lot of bikes. Lots of guys replace with tapered bearings and report good results.

 

[ANLR21]

Hey guys.

I've had my '07 for just over a week now. Rides perfect on smooth roads.

The problem is on the slightest bumps, even riding over a white line, the front gets jolted rather harshly. It's like if I hit the smallest thing at the slightest angle with the front wheel, I get knocked about right up through the bars.

I understand the fork is completely non-adjustable. Compressing the fork I don't feel any issues there. The rear shock is set to '3', normal for preload.

The tires are still stock @ 3k miles, BT-020. 33-36 psi in the tires per the swing arm label.

I've ordered a set of 'PIRELLI Diablo Supersport Street' from CG, thinking that the stock tires are old and hardened up.

Is there anything you guys would recommend checking? Thx!

darius, if you're getting smooth action out of the forks, it may well be that a prior owner used a much heavier (or just too much) fork oil. Stock fork oil weight is 0w fish oil or something that allows the forks to flop all over, the opposite of what you're experiencing. I've gone up to a 15w (I weight about 175 and push kinda hard) and .95 Racetech springs which are a great improvement, probably all I can do to improve them before swapping to R6 forks.

Drain the forks, make sure to put the right amount of oil and the best-guess oil weight back in. I'd recommend a 10w to start, hopefully you'll feel improvement overall.

 

[darius]

Just a guess, but the head bearings may be loose. Kind of a known/ongoing issue on a lot of bikes. Lots of guys replace with tapered bearings and report good results.

Steering head bearing? Thanks, checking on that in the service manual.

darius, if you're getting smooth action out of the forks, it may well be that a prior owner used a much heavier (or just too much) fork oil. Stock fork oil weight is 0w fish oil or something that allows the forks to flop all over, the opposite of what you're experiencing. I've gone up to a 15w (I weight about 175 and push kinda hard) and .95 Racetech springs which are a great improvement, probably all I can do to improve them before swapping to R6 forks.

Drain the forks, make sure to put the right amount of oil and the best-guess oil weight back in. I'd recommend a 10w to start, hopefully you'll feel improvement overall.

Good thoughts. I checked over the fork and can see no signs anyone has taken it apart to change the fork oil. I'm 150lb. Last owner was heavier, so checking w/ him just in case it was modified.

The bike had a low speed drop, impacting the bars and front fairing that may be related.

 

[iSteve]

There is no way to tell the fork has been worked on by just looking at them. The stock setup should work well for your weight. The old owner may very well have put to heavy a oil in the fork possibly even changed the spring. A lot of people when setting up suspension will use a race setup. A race setup for a heavier rider would defiantly be to harsh for a lighter street rider.

Also because the bike was dropped you could simply have the forks twisted in the triple clamps, a easy fix.

 

[darius]

There is no way to tell the fork has been worked on by just looking at them. The stock setup should work well for your weight. The old owner may very well have put to heavy a oil in the fork possibly even changed the spring. A lot of people when setting up suspension will use a race setup. A race setup for a heavier rider would defiantly be to harsh for a lighter street rider.

Also because the bike was dropped you could simply have the forks twisted in the triple clamps, a easy fix.

No clumsy marks from tools, rear shock is stock setting, last owner says it's all stock as far as he knows, previous owners were new riders and kept stock tires. With all that I'm confident the fork is stock.

I'll check for twisted forks. Thanks!

 

[darius]

So I put the bike on the center stand and prepare to weight the back to raise the front and work on the forks. I become amazed at how little I can compress the rear shock under my weight (150lb), even from the passenger seat.

I verify the shock is set to '3' (normal), so I set the rear to '2' and it gets better but nothing like the swing arm action on my 250cc. Set it to '1' and it's still kinda firm but I can load it up and compress it much better now.

Is there something wrong with my rear shock to need to be dialed down to the lowest setting for me? I would try one lower if I could.

Took it for a quick test ride and the bike feels a heck of a lot better. Maybe the super-stiff '3' at the back setting was harsh enough to upset the front end.

I picked up a nail in the back tire of my 250cc today, too. Bloody bike soap opera in my garage in the last 2 weeks.

 

[iSteve]

Did you have the bike on the center stand when you tried to compress the rear shock?

Changing the shock preload does not make a spring softer it only changes ride height.

 

[darius]

Did you have the bike on the center stand when you tried to compress the rear shock?

Changing the shock preload does not make a spring softer it only changes ride height.

At first, yes then onto the side stand. Riding feels much softer.

Doesn't the pre-load setting combine with rider weight to put the shock into the more compliant range?

 

[YZF73]

Sorry that I haven't got time today to give some more info, but heres a place to start with suspension setup, you wouldn't believe the difference once you've got it sorted (I can put a more detailed post on tomorrow as there's much more to it), anyway to get you started;

[ame=http://www.youtube.com/watch?v=mK3flKxf41U]Motorcycle Suspension - Setting Sag - YouTube[/ame]

A heads up, to obtain 30mm sag on my '07 (I ride at the track quite a bit), weighing in at 156lbs without gear, I have the rear preoad adjuster on position 6.


Hope this helps, much more to come tomorrow if you'd like?

Yamahaboyz

 

[darius]

I want to verify my rear shock still has the stock spring. Are there different colors for different weights?

Mine is black. See pics. Thanks!

 

[YZF73]

I have decided to write up a comprehensive thread of my experience tuning the suspension on my FZ6 instead of posting specific info on this thread as its quite long... already 700 words, however it will take me a couple more days to get it all sorted, I will be sure to provide a link to it once it’s done, please bear with me.

To answer your previous post...

I want to verify my rear shock still has the stock spring. Are there different colors for different weights?

Mine is black. See pics. Thanks!

The standard spring fitted to the back of my UK '07 FZ6 is also black, most likely that your one shown in the picture is also stock.


In my previous post I included a video by Dave Moss of Catalyst Reaction Suspension Tuning showing how to set sag on both the front and rear, obviously the FZ6's stock suspension only allows preload adjustment at the rear but I would be interested to know if you'd adjusted this and seen any improvements/differences?


Yamahaboyz

 

[darius]

In my previous post I included a video by Dave Moss of Catalyst Reaction Suspension Tuning showing how to set sag on both the front and rear, obviously the FZ6's stock suspension only allows preload adjustment at the rear but I would be interested to know if you'd adjusted this and seen any improvements/differences?
Yamahaboyz

Yamahaboyz,
Thanks very much for your help and info. I checked out the video and will use it to check over the FZ. The bike doesn't feel dangerous as heck anymore, now that it has the rear shock set to '1'. It's still rough but much improved.
I'll try to get some measurements, including the sag.

Pirellis are still on the way. Can't wait.

----
Update 6/14: Bike feels safe and planted with the new tires. It was the old rubber causing the harsh ride, front and back.