I added 165cc of per mamual- It doesn't feel right

[Roadwarrior]

Hello all,

I've just finished rebuilding the forks on my 1978 Gs550. I installed new inner tubes, and seals, and added 165cc of fork oil as per the geuine Suzuki manual. When I push each fork leg up and down it doesnt feel like there is much dmpening, and I can feel and here air bubles as I push them up and down. 165cc is not verry much oil, and the oil level is way down at the bottom of the forks. Is this normal? I am really tempted to ad more oil. I know I didn't drain much oil out of the forks when I took them apart.

[Anonymous]

Just for you personal interest I can tell you that my 400 only takes 3/4 of a cup of oil per side. I too have the sound of bubbles 2 weeks after rebuilding and I was going to ask too...so what's going on here? :? Even when it is -20C my 30 weight doesn't provide as much damping as I'd like when stopping. Do I need to rebuild the internal valves or something?

[focus frenzy]

Have you followed the procedure and measured the oil level?
what weight of fork oil did you use?
does your fork have air caps and have you put it the prescribed amount of air pressure?

[Roadwarrior]

The Factory Suzuki Manual says to mix 30w engine oil with automotive auto transmission fluid at 50/50 and add 165cc to each fork leg. I talked to a local bike mechanic and he said to use 20W Belray fork oil wich is thicker than what came stock but he said that thease old bike work better with the thicker oil. He looked up in one of his shop manuals and confermed the 165cc (approximatly 2/3 of a cup). The fork legs don't feel right, but I am used to modern bikes, and have never had the chance to ride the GS550 yet for any length of time.

[Anonymous]

Air bubbles are normal. When the fork is assembled and capped, it has a very large volume of air compared to a small amount of oil.
Every time you compress the forks, oil is pushed through the internal valving and will cause the oil to aerate.
If the fork action isn't to your liking, you have several options:
1) Stiffer/progessive springs which will make the action firmer through the entire travel...but it will also rebound faster.
2) Use a higher viscocity oil which will slow the dampening and rebound action down. You can mix different fork oil weights to suit your needs.
3) Add a small (key word being "small"...too much and it will ride harsh or you could blow out the seals) amount of air...air pressure rises as the fork is compressed and acts like a progressive spring...and it also causes the rebound to be faster.
4) Adjust the oil level. You can safely add or subtract some oil to fine tune the action (use good judgement...a little goes a long way).
Keep in mind that a 20 year old spring will lose some of it's strength and become shorter also, which changes the steering geometry...which in turn effects handling. And...when you change the settings at 1 end of the bike, it can also effect the other end. But generally, if things were in decent shape to start with, this won't be much of a concern. It's a vicous cycle, but if you make small changes and record what you've done..it will pay off.
Mike