Topic: fork oil 750 K4

[Donzon]

Hey:
      Quick question.  I'm currently rebuilding the front forks on my K4 CB750.  I haven't had this bike for long and have no owners manual.

  The shop manual and the SOHC page specifies 220-230 cc of 10w-30 oil
  The supplement specs are  150-155 cc of ATF (transmission fluid ??)

  Which quantity is correct?  I have gathered that there is a rather large difference between a refill and a fill from empty, but both manuals seem to state that this is the quantity after rebuild.  And whats the deal with the ATF, is that OK.

Don Ruetten

[jsaab2748]

I did my k5 forks last week. 160-162 cc of valvoline max life transmission fluid. It works good. You can also use fork oil available at cycle stores that comes in varing weights to affect damping characteristics. Not many people use motor oil, maybe back in the day when the bikes were new being the exception. ATF can transmit pressure without foaming up I'd think.

[jaknight]

Hello Donzon,

     I have a '74 CB750 K4.  I prefer a motorcycle fork oil of 10W that has teflon added to it.  I believe you can get better results with the teflon additive.

     Go to a Honda dealer and check out the different brands of fork oil available.  Pick out the brand of your choice....... I would not go heavier than 15W; fork action begins to get too stiff for me after that point........  I could not recommend going with regular motor oil........

P.S. ATF is OK; I simply have a preference for the regular fork oil with teflon added.

     ~ ~ ~ jaknight ~ ~ ~

[USN20]

Hey:
      Quick question.  I'm currently rebuilding the front forks on my K4 CB750.  I haven't had this bike for long and have no owners manual.

  The shop manual and the SOHC page specifies 220-230 cc of 10w-30 oil
  The supplement specs are  150-155 cc of ATF (transmission fluid ??)

  Which quantity is correct?  I have gathered that there is a rather large difference between a refill and a fill from empty, but both manuals seem to state that this is the quantity after rebuild.  And whats the deal with the ATF, is that OK.

Don Ruetten

I know exactly what you mean ... The (dry) capacity confusion is probably due to the fact that Honda changed fork internals beginning with the CB750 K3 model. (according to the supplement)

K2 and earlier (dry) capacity is 220-230cc

K3 and later (dry) is 155-160cc

I replaced my K4 fork seals (OEM Honda) over the winter and used the Honda supplement specification of 155-160cc. Ford Mercon V (semi-synthetic ATF) was used only because I had an extra quart sitting on the shelf. Any good quality fork oil of your choice should work just fine.

[Donzon]

  Thanks guys, that's the info I was looking for.

  I've used fork oil before, and likely will for the next change, but I also have a ton of ATF sitting around and I'd like to get the forks on ASAP.

  Thanks again
  Don

 

[merc2dogs]

 I'll tell you, I used 10w-30 once, and the whole front end was very stiff afterwards, it worked, but like I say, rode very stiff.
 planmned to change it the next weekend, but after riding it, I actually liked the way it stiffened the bike up.

Ken.