Topic: Technical question about fork oil...

[Johnie]

I have 2 projects going on this winter.  You know about my CB750KO.  My question is about a 1981 CM400 Custom with front air assist shocks.  I am changing the fork oil and see the manual says use ATF.  My dealer says try the 5 weight Maxima fork oil as it is closer to the ATF grade.  I was thinking of using the 10 weight Maxima and maybe not adding air to the shocks to reduce the possibility of blowing the seals.  Just want to get your opinions if this is what you would suggest.  I really value the opinions on this board.  I also heard Belray and Spectro is good, but my dealer does not carry those.  Thanks a lot and Merry Christmas!!!

[Tim.]

ATF is the old standby - I think they were recommending it before there was such a beast as fork-oil.

I went with fork-oil this time around, but have used ATF in the past, and the stuff I poured into my 650 forks sure looked like ATF anyhow.

[DarkRider]

Im running 20 wt Spectro on my interceptor with air assist forks. A lot of it is how heavy the rider is...5 wt is good for light weight riders under 150 lbs...10 wt for anythuing over that and to be safe 20 wt is good for anyone over 250 lbs..

[Johnie]

Thanks Outlaw...that's what I was looking for.  I sort of thought 5 weight was sort of light, but wanted some confirmation from you experts.  I will go with the 10 weight...I am over 150...  

[crazypj]

Thanks Outlaw...that's what I was looking for.  I sort of thought 5 weight was sort of light, but wanted some confirmation from you experts.  I will go with the 10 weight...I am over 150...  

Not a good idea..........
Your reducing spring rate by not adding air, then your increasing damping by using thicker oil.
 If forks are too soft you need heavier springs, then play with oil.
 Thicker oil just stops forks reacting fast enough when you hit a series of bumps, its for damping not springing.
PJ

[DarkRider]

I should have specified that im still using the bikes air assist. I have the front forks set at 4 psi in the front and 42 psi in the rear ar shock..Basicly using the system as intended just with heavier oil then stock

[Johnie]

I will do the same.  Thanks...