Fork oil weights and ATF | GTAMotorcycle.com

Fork oil weights and ATF

dirtbag

Well-known member
I'm in the midst of replacing the fork seals on my 06 KLR650 and I'm debating what to fill the tubes with. I weigh 145 lbs in my birthday suit and the suspension is stock. I know it could likely benefit from progressive springs and after market valving but for now I'm leaving it stock.

My question is what weight of fork oil would you recommend or would you add ATF (auto tranny fliud). Now before you flame me for considering ATF please realize that I've seen lots of posts where others use it in place of fork oil and the factory honda manual for 86 Goldwing states "assemble forks and add specified amount of ATF"

All help appreciated
 
Fork Oil - no detergents in it. stable viscosity.
 
I would say lighter people (like myself) generally get more out of stock suspensions. Most of the time, when people talk about "upgrading" the springs they are really just increasing the spring rate, which is generally fine as stock for lightweights.
 
OP I have 80 pounds on you and I put Motul Fork Oil Expert 15W in my FJ. $13 for a liter. Made a huge difference as far as reducing brake dive - no idea what was in it before.

At 145 lbs, I'd go with whatever your manual recommends. You're Japanese-sized.
 
My question is what weight of fork oil would you recommend or would you add ATF (auto tranny fliud). Now before you flame me for considering ATF please realize that I've seen lots of posts where others use it in place of fork oil and the factory honda manual for 86 Goldwing states "assemble forks and add specified amount of ATF"

All help appreciated
I have seen the ATF thing before, mostly in older bikes. A lot has happened in since '86 lol. Stick to proper fork oil.
 
10w or 15w, which would be the better way to go?
 
Basic damper rod forks like KLR 650, ATF is all I ever use, with or without cartridge emulators. It works.
 
adjusting the oil level can have a dramatic effect on how far your fork will dive. start at stock level. if you want a longer range of fork movement during compression reduce oil level. if your fork is bottoming, increase oil level. How does this work? it changes the amount of air volume in the forks - less air volume and the air pressure increases earlier in the compression stroke, thus stiffening the fork earlier in its stroke. less oil means a greater amount of air volume in the fork therefore stiffening up the compression stroke later during fork compression.... too much oil will lock your fork compression too early and you won't use all the travel - and possibly blow out your fork seal if you hit a huge deep bump at speed. make your level changes in very small amounts and test. Make changes in amounts of no more than 2-3 mL using a graduated cylinder. This is not a replacement for proper fork spring rates. Set your sag first.

as for atf or fork oil, I would go with proper fork oil, especially if you have a bike with newer sophisticated ss type suspension. But it wouldn't be wrong to use atf on a bike like yours. I have been told or read that atf has a viscosity of ~ 10wt fork oil. But i don't promise this, as i do not remember the source of that info. Many people would be surprised to learn that dealers may be using atf when doing the PDI on a new bike (if they even bother to check fork oil level)..

DISCLAIMER: Don't do anything i've said, as you could crash and die. Consult a licenced mechanic for any changes.
 
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