Hi there fellow CBR owners and riders.
I've got a CBR from 1990, she's in pretty good shape for her age :P but she has a problem which I can't seem to figure out.
So she's got a front suspension with air pressure and springs too. The problem starts with the fact that I didn't find any service manual to indicate the proper pressure in the fork, so we did a lot of testing. She had from 1,3 bar to 0 bars in it. The problem is that with air pressure in the fork she goes quite strange, meaning she seams to pull to the right. With no pressure inside she goes straight.
Have you ever heard of something similar? If so, where did the problem lie?
I must say that for approximately 3000km I changed the front tire, the back tire is her old one, the one she was bought with in 2007. But she did the same thing with the old front tire, too.
This week she got new simmerings and the suspension oil got changed too .
But still she's going to the right. Not too much,so that one can't ride her, but enough to feel it and see it if you ride with no hands.
Help people, I need an idea, where could this be from?
Thanks.
Dana

 

the forks are not supposed to be pressurized. the most air you can add is 1/2 bar, or 6psi, and that is like if you're a really heavy person, to help stiffen the front. if you really added 3 bars, thats like 43 psi, you might have damaged the seals, they could start leaking...
also since you mentioned changeing the oil, did you add the correct amount? the left and right forks take different amounts. left side =371cc, right side =361cc.

 

Hi and thank you for your answer.
So..if they are not supposed to be pressurized why do they have valves just like those from the tires?
I'm not a heavy person , I'm 170m tall and I weight 62 kilos.
And I think you didn't read right what I wrote, because there was a comma there : I said "1,3 bars" not 1...and 3 bars.
Like I said since we couldn't find in any service manual the correct air pressure we did some trial and error, and so we realized that with some pressure in the fork, the pilot tends to sit curved a little on her seat, and when driving without the hands she goes to the right.
With no air inside she lowers the fork but goes straight.
Can it be that from so little pressure difference she would act so different?


And an other question, I read in the service manual that with oil filter change there should be added 3,4 liters of oil, but she hits the mark from the oil cap with 3 liters.Could it be that maybe the oil cap was changed or what?

 

Start it up and let the oil circulate for about 30 seconds. Then shut it off and measure again. When the oil filter is new it is dry, and some oil will remain there after it has circulated. Top it up as necessary...

 

Thanks for your answer, but this is exactly the way we did it, and after 3 liters poured in, the stick read maximum level.
Could it be that the oil cap/stick is not her original one? Does any of you have a measurement of an original CBR 600 F PC23 oil stick to compare it with ours?
Although the oil stick looks wery similar to the one shown in the parts manual, could it be that it's not the original one? On her's it's written MN4 , no idea what that stands for