[cookey]

hi i have a cbr 250rr mc 22 what i need to know is how to tweak the suspension for my son to do track days it is very soft and i want to harden it up any info welcome thanks guys

 

[richo]

Heavier fork oil and some 20c pieces under the fork caps. What does your son weigh?

 

[cookey]

Heavier fork oil and some 20c pieces under the fork caps. What does your son weigh?

his weight is 11 stone[hr]
what fork oil would you recommended ??

 

[richo]

Heavier fork oil and some 20c pieces under the fork caps. What does your son weigh?

his weight is 11 stone[hr]
what fork oil would you recommended ??

Google suggests that 11 stone is about 70 kilos. When I last rebuilt my cibby forks I weighed 80 in gear, and used 15w motul fork oil.

I'd suggest that it's a good starting point. Or 50/50 with 10w to make 12.5w.

The 20c pieces are to add preload to the spring, try with 2 in each side and see how he goes.

 

[cookey]

cheers bud i will try that tommrow and see how he gets on how much oil dos the forks take ?? and what setting is for the rear shock

 

[richo]

Memory says 297mm for the forks, or an airgap of 139mm. HOWEVER those are both figures that sound familiar from when I last rebuilt forks.

I'd wait for someone else to chime in, or check the service manual. Or I think harry has a fork rebuild thread up on here somewhere.

For your son, and assuming that the rear shock is in decent nick start with 5 clicks of preload and go from there.

 

[shane]

harys thread:

http://cbr250.com/forum/thread-266.html

 

[cookey]

thanks guys[hr]
when you say a 20 cent peace is this an euro cent or another ??

 

[Drew]

I take it you're not in Australia then? Well, a AU20c coin is the same size as a 20p coin from the UK so you should be sweet there if you can get your hands on them, they're just a preload spacer. As far as the other options go, you could look at getting yourself some cartridge emulators as well, just don't buy brass ones, brass slivers end up in the fork oil and screw everything up.

 

[cookey]

ok should b abel to get a few of them i live in ireland what is a cartridge emulators ??

 

[Drew]

Well, the way that a CBR damper works is as a simple orifice damper, so its just got a piston with a few holes drilled in it. Newer bikes on the other hand have a piston with shims on it, which bend out of the way under load to give you "proper" suspension behaviour.

The problem is that an orrifice in a piston gives you damping which goes up to the cube (or something like that) of the oil velocity through the orifice. On the other hand you want a linear oil velocity to damping ratio, so newer pistons have a different design which is a lot more complex... the other alternative is that NSR 250 forks have cartridges which will give you much better body control as well as better and more tunable ride and should bolt right in to the CBR yolks (I think Mootavic has done this mod and liked it).

 

[studricho]

The NSR250 fork mod is a very good mod. I have done it myself and apart from the bigger forks the bigger brakes are awesome.

You do need to machine some of the length away from the bottom of the head stem under bottom triple clamp, press it through so that it's exactly the same length as the MC22, machine off extra length not needed and re weld.

Sounds complex, but it's an easy job. You also have to cut away the stops and re weld to a new spot so they work.

You get to use your front wheel, guard and all the switch gear that you used before.

You'll need the NSR brake system and the clip ons.

If you can get a front end cheap, then it's a great mod.

 

[cookey]

i put 2 washers in and sum 10 fork oil but am going to change it for 15 but the coins/washers are a good mod thanks guys

 

[roobars]

Memory says 297mm for the forks, or an airgap of 139mm.

The workshop manual says:

"fully compress the fork pipe and fill with ATF to the standard level"

Standard level 114mm (air space fully compressed)


Theres also some bs about air pressure..... I might have an old manual