Tyz Fork Oil

[fivebunny]

Hi all.

I'm going to freshen up the forks on my TYZ, strip them down and give them a good clean. I have a manual but its in Japanees (got it off ebay and the bloke still selling them dispite my complaining so dont buy one) so have no idea what weight fork oil to use and how much in each leg. Also should i put a different weight oil in in relation to my weight to make a differance? (16st)

Thanks in advance for any help or info.

[woody]

Found this that I posted for someone else some time ago. I used to use 10W and it was fine for me and I'm 17.5 stone.

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From memory...

First loosen but don't remove the allen bolt at the bottom of leg before starting to dismantle as the spring tension should enable you to undo it without holding tools, especially if you have an air/electric ratchet and you compress the leg whilst undoing it. REMEMBER, the damping adjuster screww is inside the head of the allen bolt so screw it right in before inserting the allen key, otherwise you may damage the adjuster screwdriver slot, it's only brass (bitter experience) Count the number of clicks for resetting it afterwards.

Undo the fork caps from the stanchions. Once undone, the fork caps are still screwed onto the internal damper rod and secured with a locknut underneath them. To remove the cap from the damper rod you need to hold the locknut with a spanner and undo the cap. Bit fiddly as the spring/preload spacer is in the way. You can then remove the spring and spacer etc. making a note of their fitted order.

Turn fork upside down and pump out oil, also pump the damper rod as this holds oil too.

Then remove the allen bolt from the bottom of the fork leg, hold the fork leg in one hand (or vice) and pull the stanchion sharply out. You probably need 2 or 3 goes to shock it free of the bushes. Watch that the damper rod doesn't fly out and disappear as it is now free, no longer held in place by the allen bolt. May be better to remove it before trying to shock the stanchion free. This is the messy part as when they seperate, any oil left inside will come out.

Once the stanchion is out you can replace the seals and bushes, just note their order before sliding them off.

Reassembly is the reverse.

To fill with oil you need the leg upright with stanchion fully extended but no spring. Fill to the top with oil, then pump the damper rod 7 or 8 times slowly through its full stroke to distribute the oil internally. The level will drop. Refill to the top and then slowly pump the stanchion itself 7 or 8 times but not quite right through its full stroke to completely distribute all the oil. The oil level will fall again. You are looking for an air gap of 95mm from oil to top of stanchion (Birkett's recommendation to me) Add or remove oil as needed.

Refit spring/spacer and cap and screw cap back into stanchion.

Think that's it, been a long time so I may have overlooked something but I don't think so. Reset your damping adjuster in allen bolt in bottom of fork leg back to original position.

[fivebunny]

Hi Woody.

Thanks for the quick and informative reply.

I just have one question. If when you fill the leg with oil for a second time to the top is it to be in the compressed position? If it were extended position and filled, on the first compression would the oil not spill out. A bit confused, but then it doesn't take much!

Thanks once again.

[woody]

Yes, fully extended, but this is the bit I can't rmember too well. You need enough oil to ensure that the internals are immersed in oil so that when you move the stanchion down, which draws oil into the chambers, it only draws oil and not air. If in doubt leave about an inch or two gap to the top and keep an eye on the oil as you slowly move the stanchion down. The level should drop a bit as the stanchion moves down, spreading the oild thorugh the internals, but if it looks as though it is going to spill over, empty (pour or use a syringe) a bit more out and try again but if you do, be careful not to let any air into the damper internals or you'll have to start all over again with the damper rod bleeding.

Hopefully you can marry this up to the pictures in the manual

By the way, the manual says something like 440cc of oil per leg but it's too much. I think Mick Andrews used to say 400cc but whether you use the volume or the air gap method, you still have to go through the bleed process to distribute the oil fully through the internals. I've been told that if you just put 400cc into the fully assembled forks in situ in the bike and them just pump the forks a few times, it is enough to distribute the oil. Fact is I don't know the answer to that, but given the specific process Yamaha give in the manual, I'd say that the air gap method is the only and correct way.

[fivebunny]

Thanks again.

I take it when measuring the air gap I have the leg extended and the spring out?

Once again thanks for the info.

[woody]

Yes fork extended and spring out and ideally damper rod fully extended. Unlless it is held fully extended it will sink back into the leg under its own weight. Bit of a 'fussy' process but no other way with cartridge forks. Old style damper rod forks don't work as well as cartridge, but so much easier to service...