how do you know if there is to little oil in the forks?

[Spiff]

After I replaced the fork seals, and put in new progressive springs I filled the forks up with the recommended amount according to the servicemanual(180cc).
But the front end seems very soft when bouncing the bike up and down.
Also, if I hold the front brake and rock the bike backwards it'll "settle" in a slighty higher position. If I rock it forwards again it'll go back to what it was previously at. Is that normal behaviour? Maybe should try and make a video...
I have no experience in what this bike should feel like since it's my first one and I have only ever driven it properly twice for a total of one hour. That was last fall so I can't remember how it used to be either....

Should I just remove the forks again and fill it up to the maximum of 150mm as stated in other servicemanuals? The papers that where included with the springs said 150mm was maximum, but didn't mention any minimum oil levels... I think mine are at like 200mm or something...
This is all on a '78 750E

[7981GS]

I am not close to a factory manual at the moment but, the Clymer manual says 180cc's or 6.04 oz.

Eric

[bonanzadave]

Cliff has a great tutorial on his fork springs.

http://members.dslextreme.com/users/storagecliff1/images/Install_Progressive_Fork_Springs.pdf

Take note on the specific wt fork oil he used and the spacers he made to go on top of the springs.

[Spiff]

Yes, I've read that.
But the papers that followed my fork springs says my bike doesn't need spacers. Nor where there any spacers with the factory setup either.
I used fork oil, 10weight I think...

[hampshirehog]

Have you set the static sag?

[DannyMotor]

10 weight... 1liter bottle should be enough to do both forks... most forks, twice.

If you put the new springs next to the 2 springs that were in there... are they the same length? If not, you need to cut spacers.

Fork oil will not affect how far the forks dive or sag... The AMOUNT of oil will affect the AIR cushion in the fork ONLY... and this is based more in rebound and compression damping than affecting sag.

Take a zip-tie, zip it to your fork above the seal, push it all the way down til it touches the seal.... sit on your bike (DO NOT BOUNCE ON IT). Shimmy the zip-tie til it touches the seal, and then carefully get off.

The difference from the top of the seal, to the bottom of the zip tie is your sag... this should be 32-35mm. Any more than that... you need a spacer to UP your PRELOAD on your forks. The PRELOAD.

So, say your sag is 50mm. You should cut a spacer that's around 30mm to start (one for each fork) throw them in (between the top of the spring and the bottom of the cap) and then re-test your sag. This should get you in the ball-park.

[Spiff]

The old springs where a bit shorter than the new ones, due to old age and sag.

I did the zip-tie thing, and here's what I did:
I tied the zip around the fork leg as said, then took the bike of the side stand, pulled the zip down to the seal, then sat down on the bike. The forks compressed a little, I then stood up and nothing happened. It didn't extend like I thought It would/should(?) do.
When I put the bike on the side stand it did extend a little. I measured it to be around 28mm from fork seal to bottom of zip-tie.
Is it suppose to behave like that? Did I do something wrong, it's just that I find it a little weird that it doesn't extend until I put the bike back on the side stand again...