What will thinner oil do to the fork?  Make it react more quickly?  The dirt bike seems to pound when hitting bumps and I wondered if thinner oil will help it soak up the bumps faster.

My guess it works the other way, a thicker oil is more viscous and probably has more of a damping effect.

Thinner oil will provide a smoother ride to an extent.

But, from what I understand... Thinner oil can make it so the shocks bump so much that the front tire just bounces down the road...

i guess you can think of it sorta like a paddle in the liquid.  thicker it is the slower you can paddle, thinner the faster.

Quote from: RVertigoBut, from what I understand... Thinner oil can make it so the shocks bump so much that the front tire just bounces down the road...

Yes, thinner oil reduces the vibratory damping effect of the forks.  Not a big problem on a dirtbike I don't think.   :mrgreen:

lower weight = softer

just get a few different weights of oil and play with them.

I'm trying to remember what I used a while back in my old dirtbike to get a nice smooth ride...brake fluid, I think...I wouldn't suggest using brake fluid, but finding something of similar weight.

DO NOT USE BRAKE FLUID!!!

It will destroy the seals and probably ruin the forks because you can never get all of the contaminate out!

ATF is probably ok, but you can never be sure of its viscosity.  Best bet is to shell out the money and buy specific motorcycle fork oils.

Varying the oil viscosity changes both the compression and rebound damping. Thicker slows it down, thinner speeds it up.
If the bike is actually bottoming out over bumps, its probably that the springs are worn out and/or to light a spring rate.

john,

pound....as in compress all the way and make noise or compress a very little bit then turn into rock

most bikes are under damped and under sprung
therefore you will probably be changing the oil to 20W or 30W
most stock stuff is 5 to 15 W
also you might want to add some spacers

ya know kinda like a GS....

if it is the second ...version of pound.... the fluid level might be to high and is hydrolocking the forks

Shelled out the $10 for forl oil - 5w.  The shocks are oversprung for a 200lb bike and over dampened.  The 5w was much thinner than what came out and the bike absorbs bumps much better now.

Thanks for the advice people!

John, check out www.thumpertalk.com  they got a section devoted to setting up susspension.

Quote from: JamesGDO NOT USE BRAKE FLUID!!!

It will destroy the seals and probably ruin the forks because you can never get all of the contaminate out!

It didn't cause mine any damage at all. :lol: (may have been powersteering fluid, though....  :dunno: )

I said not to use it anyway. :nana:

I would suggest against using ATF, though...especially if you think brake fluid is going to cause damage.  I use ATF to disolve the crap build-up in rotary engines and to clean parts...NOT a soft-part friendly substance.

ATF doesn't attack seals. Otherwise how would it stay in transmissions?

Until specifc motorcycle fork oils came out, using ATF was the recommended method for lightening up fork damping.

really?  considering the damage I've seen it do to built up crap inside rotaries and how well it tends to strip paint of other debris from parts I'd have never thought it a good idea.

All the gasketed surfaces in a tranny are between two pieces of metal.  Water will disolve paper but waterpump gaskets and stuff are made of paper.

Quote from: makenzie71really?  considering the damage I've seen it do to built up crap inside rotaries and how well it tends to strip paint of other debris from parts I'd have never thought it a good idea.

Gasoline will do the same thing for engine parts but it doesn't eat the rubber carb parts or boots right?

Quote
All the gasketed surfaces in a tranny are between two pieces of metal.  

Not the rear or output shaft seals.

Quote
Water will disolve paper but waterpump gaskets and stuff are made of paper.

Because they are waxed, oil saturated, or plastic..

I do know what I'm talking about.

Quote from: JamesG

Quote from: makenzie71really?  considering the damage I've seen it do to built up crap inside rotaries and how well it tends to strip paint of other debris from parts I'd have never thought it a good idea.

Gasoline will do the same thing for engine parts but it doesn't eat the rubber carb parts or boots right?

No it doesn't.  If gasoline did the same thing then carbon deposits wouldn't exist inside working combustion chambers.  They're subject to gasoline everytime they're run.

Quote
Water will disolve paper but waterpump gaskets and stuff are made of paper.

Because they are waxed, oil saturated, or plastic.[/quote]

I've never used a waxed gasket, oil saturated, or plastic gasket on a water pump assembly...or really anything else in an engine.  I've rebuilt more 12A', 13B's, 5mE's, 5mGE's, 6mGTE's, 7mGE's and 7mGTE's than I care to remember.  Always dry gaskets, an none composite except the headgaskets.

QuoteI do know what I'm talking about.

I'd be very happy to apologize if you'd simply point out where I said you didn't.  I know a few things myself.  You introduced something new to me.  Take things like that as compliments instead of wording yourself to make it sound like you think they're an idiot.

I'm just cranky 'cause I'm stuck in Iraq for another 5 months without a bike to ride.
:x
sorry.

My point was ATF doesn't hurt fork seals.

Quote from: JamesGI'm just cranky 'cause I'm stuck in Iraq for another 5 months without a bike to ride.
:x
sorry.

My point was ATF doesn't hurt fork seals.

I gotcha man, no problem.