Tyz 250 Fork Seal Replacement

[izzywithus]

Hi guys, I've just got a TYZ 250 Scottish as a project bike and the fork seals are leaking, as well as lots of other things which need repairing.

Could someone tell me how to change the seals please? I looked in the archives but could not see a description.

Secondly, where can I get a service manual for the bike it is a 1996 or 7.

Any help would be great. Thanks.

Cheers

Iain

[woody]

From memory so a little sketchy now.

If you haven't got the tool to hold the damper rods and stop them spinning, first thing to do is loosen the allen bolts at the bottom of the fork legs with the forks still in one piece and hope that the spring tension holds the rods. Best done with an air ratchet if you have one. BE CAREFUL as the damping adjustment screws are located in the head of the allen bolts. Screw these right in before you shove an allen key in them as if you don't you will damamge the adjusters which are brass and fragile. If you're lucky they won't be seized. If you can't stop the rods turning they will just spin around with the allen bolt. Assuming you can undo them, one way or another, just loosen them a turn or so for now, don't take them right out or you'll have oil all over you. If you have got the tool, ignore this bit and move onto the next bit first.

Undo the fork caps all the way - they won't come away as they are screwed onto the top of the damper rod. The spring length will keep the spring tensioned against the bottom of the cap even when removed. You'll then need to pull the spring down slightly so you can get a spanner on the nut under the fork cap. Hold this nut steady and you can undo the fork cap from the damper rod. You can then remove he spring, the spacer tube and a shim. Make a note of how it all fits before removing. I think you can now also remove the cartridge tube as well.

You'll now need ot get all the oil out and you can only do this by holding the fork upside down and pumping it out using the fork tube. As they are cartridge forks it won't all just pour out, it needs pumping.

Once the oil is out remove the allen bolt from the bottom of the leg. To then remove the tube from the slider, first remove the dust cover and look to see if there is a circlip in there holding the seal in place. I don't think there is but can't remember, so check just in case. Hold the fork leg in one hand and the slider in the other and pull the slider as hard as you can to jolt it free of the fork leg. The only thing holding it now is the tight fit of the bushes. If you yank it hard enough you can pull it free. Once out you can see the seal, thick shim/washer and bush. Make a note of what order they are in.

You can now remove the seal and replace with a new one. Once done and all of the old oils is removed you can start reassembly. With the seal, bush and shim all in place on the tube slide it back into the fork leg. To get the bush past the top of the leg you will need to tap it through. There is a tool for this but if you don't have it you will have to improvise with something. I use an piece of tube that will slide over the fork tube which can then be used to tap the bush, seal and shim down into the fork leg. You can't push them in with fingers. Once you have driven them home the cartridge can go back in and the allen bolt refitted to hold the leg onto the tube. Same principle applies for tightening this as undoing.

You now need to fill with oil before refitting the spring. You can't just fill the forks, you need to bleed them to distribute the oil throughout the internals, as they're cartridge type. The oil level should be 95mm from the top of the tube with the tube fully extended. To do this is a bit fiddly as first you have to fill the forks to the top, ensuring that the cartridge/rod is covered. When full, get hold of the top of the rod - not easy with fingers, you may need pliers or such like. Pump the damper rod up and down SLOWLY about 6 - 7 times to evenly distribute the oil. You'll notice the oil level go down whilst you do this as the oil is working through the internals. Once you've done this, refill the forks again to the top. This time pump the outer tube SLOWLY up and down but for a MAXIMUM STROKE of 6 inches. The oil level probably won't drop much at all when you do this stage. When done you need to set the level. You can either syringe the excess out or carefully tip it out, syringe with tube is better. Oil weight is personal preference but you should be fine with 10W.

Once you have the oil level set, replace the spring, spacer, shim and nut , refit the caps by holding the nut and screwing the cap back onto the top of the damper rod. Then, unscrew the damping adjusters in the bottom of the forks to their original setting. Screwing them out softens the damping.

That's about it. If anything above is wrong or in the wrong order it should be apparent as you work through. Pretty sure that's about it though.

Edited October 24, 2009 by Woody

[izzywithus]

Hi Woody, that's great! I will have a go and let you know how I get on.

Thanks.

Iain