SOHC.co.uk Forums > CB350/400
Changing fork oil.
Bradders:
Thanks Ted and Micky. Do I need to take the springs out at all?
McCabe-Thiele (Ted):
When I did my 400 fork oil change I removed both cap nuts, then drained the oil. Consequence was both springs then pushed upwards making it much more difficult to get the first cap back on.
McCabe-Thiele (Ted):
No need to take the springs out, if you do for some reason make sure you put them back the right way round.
Don't ask which way round, was it the coil spacing or is that the valve springs?
Bradders:
Thanks Ted. I will leave the springs in. Thanks for your advice.
honda-san:
The genuine Honda shop manual needs to be read carefully as it covers both the 350/4 and 400/4.
400/4 takes 145 /150cc of oil per fork leg at oil change, 160/165cc if completely stripped (the 105 and 125 cc figures suggested previously are for the 350/4).
I have always (well, every 6000 miles over a total of 250,000) simply drained one leg at a time and re-filled with 145cc, and not worried about removing the spring nor about the air gap - just put the correct amount in.
As to which way round springs go, variable pitch springs should always be fitted with the closely spaced coils at the non-moving end. In the case of valve springs this means against the cylinder head to minimise the spring mass that is moving as the cam operates, and therefore to minimise inertia effects at very high rpm's which contribute to possible valve bounce. For fork springs it is much less important as the change in moving mass due to spring orientation pales into insignificance against the mass of the rest of the bike and rider which is going up and down. Still best practice though to fit the close coil end of the spring into the fork leg first.
FWIW, my day job for 35 years was as a design / test / calibration engineer at a company that provided consultancy services relating to spring technology.
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