GPZ400R Suspension Problems

[crazymotorbik...]

Hey,

Ive recently rebuilt my GPZ400R. The only problem with it now is the front suspension.

I filled the suspension with the correct amount of medium fork oil. But the forks are rock hard, and thats with little air pressure in them (Ive also tried with air in, and it makes no difference). When i go over bumps the forks do not retract very much which results in a very bumpy ride.

It did pass its MOT like this.

Now im thinking maybe a thinner oil would help? Any help or advice is gratefully recieved.

Shaun.

[Gpz 900R]

Does it have the anti dive system fitted? if it does my money is on them being seized,you could also try a different grade fork oil.

[crazymotorbik...]

The anti dive fitted was stripped and cleaned and i know 100% that it works.

I think the problem is i put the wrong amount of oil in. There is no specification for the amount of oil that goes in due to the bike being an import

Any info on the level would be most helpful.

Cheers,
Shaun.

[Jebus]

if you have a hunt for a service manual for it if may be in japanese but might be about to find a translated version. If i am right, not fully sure but the gpz400 is basicly a sleaved down gpz600, that was a offical bike in this country, if you can find the needed information for that bike then maybe use that as a starting point?
____________________
2nd time around CBT: 8/9/11
125 Varadero

[Gpz 900R]

I think you will find that the oil is measured when its in the forks, you will need to put some in then measure the distance from the top if the fork leg,the best way is to use a syringe with a weighted hose of the correct length then just drain off the excess via the the syringe, they are i'm 99% sure the same as a 600, these people here are worth contacting.

https://www.bartonmotors.co.uk/

Keep us posted on how you get on, good luck.