A question about taking a nose dive.

[RichV]

The nose of my XS11 is diving way too far when I brake. I replaced the tubes last fall after XSSE because of the surface rust but that didn't change things much. If anything it got worse.

Is there anyway to improve the front forks to reduce the dive? Last year someone, I think Marty, recommended adding more fluid but I don't know how much too add. Are there better springs out there that will improve this?

Thanks again for the help.

[ViperRon]

When I got my bike new I purchased it with a kit including fairing and saddlebags to be installed by the dealer. It came with new rear shocks new springs for front forks and they did some modifications also. Replacing the vacuum on the pickup coils taps into the exhaust pipes so I know for the bikes with fairings there was an upgraded spring. I would empty out the oil in the forks and refill and if they are air forks put the proper amount of air in. With a fairing it increases.

If oil is old it can change in viscosity and if dirty can have an effect on the emulators making the front either squishy or hard. New springs and specific emulators are not cheap Marty got a shop to do his.

[BA80]

I had that issue with my SG also. Changed the oil, went with 15w, and resealed the forks. Now running that and approximately 18psi air pressure and it does well.

[TopCatGr58]

Rich,

As was suggested, slightly heavier fork oil can increase the resistance to flow of the fluid thru the dampers and can help reduce the dive affect a bit, but can also make the ride a little stiffer because the wheel won't bounce as easily/quickly over a bump.

There is a spec to the length of the OEM springs. I checked mine when I did my fork upgrade both the first time, and then in 2000 when I put new fork tubes on, and again just a couple of years ago...and they were still within the spec length. However, with my over length tubes, I have to have 4" spacers inside the tubes. I don't like having to mess with the air shock portion....kinda difficult to get a precise pressure and such. SO...I then tested increasing the preload tension of the springs by using slightly larger/longer spacers.

Made some slightly longer, like 5" if I remember correctly, used some 7/8" OD thick walled black pipe. I think it was too long, and ended up with just 4.5" long...so only a 1/2" actual additional preload shim thickness since yours are stock, you should not have a spacer in there.

Jacking up the front end to take the pressure off of the fork tubes can make it easier to take the fork caps off and be able to put them back on especially with spacers. And makes it easier to put fork oil in from the top as well vs. trying to squirt it in thru the air shock valve even with the valve core removed.

T.C.

[ViperRon]

If you want to put it on threw the air holes get a large syringe like vets use so you can put a measured amount in. What I found helps it to create a long flexible hose, is to use a piece of heat shrink tube and put it on the syringe but go slow takes a little time to go in. One more added benefit of using TC's method of increasing pressure on springs instead of preloading air is you do not have a constant pressure on the oil to force it out the seals if they are old.


The only issue with taking caps off is if you do not have good hand strength. You have to put even force on the spring and push it in and then evenly thread it back in. The only time it can get tuff is when a previous PO has messed up the starter thread.

[jetmechmarty]

Rich,

With the forks collapsed and the springs removed, add fork oil until it is 130 mm from the top of the fork. That should make a big improvement.

A change from 10 to 15W will slow high speed damping. I don't believe it's the solution.

My XS650 had preload cranked up, 15W oil, etc. I raised the level to what I'm recommending, back to 10W oil, and removed the preload. I'm now enjoying the bike.

If oil is old it can change in viscosity and if dirty can have an effect on the emulators making the front either squishy or hard. New springs and specific emulators are not cheap Marty got a shop to do his.

No. I did them myself.

[RichV]

Just so everyone understands this, I replaced the fork tubes a few months before storage. At that time, I cleaned all tube components and measured the springs for spec length. I replaced the seals and added the specified Yamalube fork oil in the exact amount.

I understand the springs caps are "hard" to install but I've done it many times on the bench. I do like the idea of holding up the front end to aid in compression.

I'm going to try Marty's approach and see if that does it before increasing the oil viscosity.

Has anyone tried increasing the air pressure? It's my understanding that it really doesn't affect the movement of the oil but overpresure can blow the seals.

[jetmechmarty]

Too much fluid means less movement and risk of blown seal. You can extend the forks and fill them with any liquid you want and they won't move. You may even remove the springs and ride until the seal fails. Too much oil=harsh ride.

If the air space is too great, you go up and down like a Pogo stick. Limiting the space for air to occupy in the fork will greatly affect the speed of nose dive. You can keep the 10W oil and your high speed damping will not be affected.