Transmission fluid or oil cb360 forks

keeleydavis

keeleydavis

Been Around the Block
Hey guys. My cb750 manual said I could use transmission fluid or wd-30 so I used wd-30. Now my cb360 manual just says transmission fluid. Would there be a problem using wd-30 in the cb360 forks or should I just got get transmission fluid? Thanks much.
 
Dump that, go to your local motorcycle store and buy yourself some fork oil. It comes in different weights which in the short of it, relays to the stiffness of the forks.

Transmission oil was considered an alternative because that's what was available back then. I have a cb650 that I run 20 weight oil in where my wife's sr250 cruiser gets 10 weight.

Same deal with brake fluid. my says dot 3 but now there's dot 5 which I put into mine.

My experience and 2 cents
 
jay_kent said:
Dump that, go to your local motorcycle store and buy yourself some fork oil. It comes in different weights which in the short of it, relays to the stiffness of the forks.

Transmission oil was considered an alternative because that's what was available back then. I have a cb650 that I run 20 weight oil in where my wife's sr250 cruiser gets 10 weight.

Same deal with brake fluid. my says dot 3 but now there's dot 5 which I put into mine.

My experience and 2 cents
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+1, I agree with every word of this. The qualities of modern fork oil far out weight the crap we used to put in forks...
 
What I was told by the local Honda shop here is that Transmission fluid dex merc 3 or something like that (whatever the manual says) is the best for old bikes and what the manuals call for... I asked why do they make the specific fork oil weights and why should I not use a specific fork oil in my 1971 CL450 and they said because the dampening is different and for fork oil to work in a vintage bike you would have to drill more holes into the stancheon tube, (?). I think that's right, for the newer fluids to work properly. Old forks aren't designed for a super lightweight oil like 5w, 7w, 10w... I'm not a professional but that came straight out of the mechanics mouth at one of the biggest shops in this area... I would say ask a professional you trust and see what they say.
 
jay_kent said:
Same deal with brake fluid. my says dot 3 but now there's dot 5 which I put into mine.
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You do know that DOT 5 brake fluid and DOT 3 or 4 are not compatible, right. You should never put DOT 5 in a system that previously had DOT 3 or 4 in it, as gelling can result, causing brake failure.

The only difference between DOT 3 and DOT 4 is the temperature rating of DOT 4 is a bit higher. The two can intermix and are interchangeable for all but racing circumstances where calipers might get too hot for DOT 3. Both are glycol based. DOT 5 is a silicone fluid. Just because it has a higher number does not make it an upgrade. In fact, it is more compressible than the glycol fluids.
 
AlphaDogChoppers said:
You do know that DOT 5 brake fluid and DOT 3 or 4 are not compatible, right. You should never put DOT 5 in a system that previously had DOT 3 or 4 in it, as gelling can result, causing brake failure.

The only difference between DOT 3 and DOT 4 is the temperature rating of DOT 4 is a bit higher. The two can intermix and are interchangeable for all but racing circumstances where calipers might get too hot for DOT 3. Both are glycol based. DOT 5 is a silicone fluid. Just because it has a higher number does not make it an upgrade. In fact, it is more compressible than the glycol fluids.
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Also, to add to ADC comment, DOT 3 and DOT4 absorb water. This disperses it throughout the system. DOT 5 does not. Any moisture getting into the system stays as a liquid, collecting in the low spots (the Caliper). On a long stop, the caliper gets hot and can cause the water to boil. Steam is not good for braking. DOT5 is used in racing, as the fluid is drained and replaced often. You also have to consider comaptibility with gaskets and seals.

ATF was recommended in the 70's on the old CB's. ATF is not an "Alternative" , but exactly what was recommended. Fork oil existed then too. ATF has anti-oxidants, anti foam agents, anti corrosion additives. An Automatic transmission is a harsh place for hydraulic fluid. ATF is hydraulic fluid with additives. Good one for the fork application. If you are racing, and changing oil after after every race, fine, use what you need. But ATF is not wrong, or bad, if originally recommended.

There is nothing wrong with ATF, other then the viscosity can vary slightly from brand to brand.

I use ATF in my CB360, 10W Fork Oil (per the owners manual) in my 91 CB750.
 
keeleydavis said:
Hey guys. My cb750 manual said I could use transmission fluid or wd-30 so I used wd-30. Now my cb360 manual just says transmission fluid. Would there be a problem using wd-30 in the cb360 forks or should I just got get transmission fluid? Thanks much.
Click to expand...

Transmission fluid actually is a pretty good fluid for forks if it has enough viscosity for the particular application. It has anti-foaming properties, and I used to use it in my motocross bikes, with a little 90 wt gear oil added to increase the viscosity.

Surprisingly, there really isn't a viscosity standard for suspension oils, so a 15 wt from one supplier may not be the same viscosity as the 15 wt from another supplier.

As a general rule, I prefer a little more spring pre-load, and more damping than most suspensions come with from the factory, so I go with a higher viscosity than they recommend. 15 wt fork oil has become my standard.

I know lots of people who just use motor oil in their forks, and it works just fine. I put Mobil 1 15W-40 in the forks of my GS450, and I liked it just fine. Just a tad on the stiff side, but with extra pre-load, it worked very well romping in the twisties.
 
Even my "modern" bike (1998 LS650) has Dex 3 as its fork oil. Inexpensive, works fine. In fact, the engine gets the same brand of 15W40 since it has enough zinc in it for the old fashioned cam and followers... Super Tech. Yep, cheapo Hellmart house brand oil. If your engine is old fashioned enough to run the cam in the head casting instead of in bearings, you need to be doing the same thing.

Modern motorcycle oil and fork fluid are for higher tech systems than most of the bikes on the board. Kind of sad, the 63 Honda cam has actual bearings and the 98 Suzuki cam relies on the head castings to be the bearing surfaces...
 
Sometimes i wonder where you guys get all that info from. I guess i could ask a question about a radio-controlled boat and you guys would still now wich way to mod it for best results. That's why i love this site!
 
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