suspension options

Well in terms of improving the front end... it's gonna be a matter of hunting around for a set of forks that have the same length as the FZR250 forks. Perhaps start off with the ZXR250 as they've got the USD forks. Aside from that, perhaps just upping the preload with the $0.20 piece trick.

As for the rear, i think it's gonna need a shock rebuild in the least. Otherwise, same deal... start searching around for something a little more sophisticated than the FZR250 part.

 

be sure to let us know your findings

As for front end, i mentioned in another post that a TZR250(3MA model) front end MAY bit our bikes.
I'm not sure what that would do to your suspension geometry though.

 

The 3MA has the same forks as the FZR... the 3LN series anyway.
There was also the 2MA, which came before the 3MA (duh!), which has parts common with the 2KR

The forks that would be the go are from the 3XV TZR250. USD goodness, plus the front wheel, rotors and calipers are shared items. I am almost certain that the main stem is the same length too.

Another avenue might be to keep an eye out for a set of forks from an RGV250, and graft them onto the FZR. I thought about this one, because RGVs are more common than TZRs, but never got too indepth with it, mainly because of the money side of things. With this method, you would have to purchase a complete front end... ie wheel, brakes, clipons etc.

Anyway, good luck with it if you go ahead with it all... Let us know how it turns out, so we can all drool over possibly the only FZR250 with USD forks <!-- s --><img src="{SMILIES_PATH}/icon_biggrin.gif" alt="" title="Very Happy" /><!-- s -->

 

have a look at the RaceTech site...

You should be able to fit cartridge emulators into the front forks.

All the information is on the racetech website, but essentially:
The FZR250 front forks use rod damping - basically oil is forced through holes of a fixed size which provide damping for suspension travel in both directions. It relies on the viscosity of the oil to create the damping effect. Put in thicker oil and you get more damping - thinner oil and you get less.
But the problem is that (due to the physics of passing fluids through fixed holes) the damping that is provided by a rod system increases exponentially with the speed of suspension travel. So if the suspension is compressed twice as quickly then the rod system actually provides four times as much damping… Which is why sometimes you will feel like the suspension is bottoming out (like going up a sloped gutter) when in fact the suspension is providing so much damping that there is almost no suspension travel at all.

To counter this, the FZR uses a lighter / thinner oil, and a softer progressive spring. If you change these (thicker oil / harder spring) you will feel it get firmer with low speed suspension travel (such as taking corners and braking), but you will create excessive damping at higher speed suspension travel (like hitting pot holes) and it may have a negative effect on traction.

Unlike straight rod damping, cartridge damping uses flexible shims / washers to vary the size of the hole that the oil is forced through. With low speed suspension travel the shims are mostly straight (thus the holes are mostly closed), providing firm suspension damping. At higher speed suspension travel the shims flex and allow more oil through, thus providing a non-exponential increase in damping. By varying the strength of the shims you can change the damping effect (both on compression and rebound), and you can do it for various speeds of suspension travel.

You can also play around with these effects by putting in firmer springs, and thicker oil, as the impact of these modifications are adjustable (where as they tend not to be with rod damping systems).

 

Cheap and easy fix is a set of stiffer springs and oil change both ends. At least then a reasonable static sag will be acheivable. Unfortunately the suspension on both ends of the FZR250 is fairly basic so any significant improvement is going to be from substitution from another bike. In terms of front forks I would be leaning to something along the lines of the RS250 as they are alot better design than the RGV and lots of incremental upgrades are available. There are a few other bikes using those forks but the only other that I can think of at the moment is the XB series Buells. As for the rear, just go visit a wrecker and ask to see his selection of rear shocks. You'll no doubt find something near enough in length from a quality manufacturer that can be fitted.

 

With different size forks you may have to change the entire front end:
- The way the forks attach to the wheels will be different, so the fizzer wheel will no longer fit.
- The forks may be too thick for the tripple clamps, so new tripple clamps may be necessary.
- If this is the case then the clip ons will also be the wrong size, and you'll be needing to change them
- Different tyre profiles and rotation speeds of the speedo cable will mean your speedo will be out (if the new speedo cable even fits the old dash). Maybe you can adjust this? otherwise a new dash is on order.

As was said above, you would basically be looking at a total overhaul of the entire front end: something which is remarkably expensive to do on an otherwise low-value 250. You certainly wouldn't see a return on your investment when it comes to resale, and I would even argue that the difference in ride wouldn't even come close to justifying the cost.

Hence why i sugested race tech ( <!-- w --><a class="postlink" href="http://www.racetech.com">www.racetech.com</a><!-- w --> ). From what i hear it provides very adjustable suspension that has a much firmer feel - for only a fraction of the cost of replacing your entire front end.

 

How about fzr 400 rrsp for the front end and back shock ?

 

I found that the 2KR have two preload settings on the front forks... also 10ml of oil makes a BIG difference...

So 10ml per fork of regular 10W fork oil and a new set of bushes and a slightly higher preload makes the forks perfect for me at 75Kg

 

What do you suggest for a 3ln 1 with a 70kg guy on it and I comute about 85km a day.

 

Hmm how do I explain...

there is a clip that holds the plug right at the top of the fork... you can puch down on the plug (after removing the rubber one) with a steel tube or a bar of some sorts... than you can move the wire clip ether up or down as there should be (and on some bikes there is rust there so bad you cant) a little identation for the clip... there are only 2 settings and most of the forks I have seen are set to the low preload which is the top indentation for the clip...

I'll take some photos and post them here...

 

That is what I mean

 

3LN are actualy easier I think... just unscrew the cap and stick a 20c coin on top of the spring and screw back up...

Works for the CBR250RR... Also a bit more oil than factory recomendations will stiffen up the suspension as there will be less air to compress...