Changing Fork Juice

[dthemic]

I would like to change the fork oil and i need to call upon the vast combined technical knowledge of the board.

Now, the question is...do I remove the forks or do I remove the bolt on the bottom of the fork and let it drain? I could then reinstall the bolt and remove fork cap and add fluid? Sounds too easy to be true. A fellow with a lot of years experience tells me the easy method will work. What do you all think?

The bike is within arms reach as I type. The wheel is removed and I am ready for plan A or plan B.

And other related query. Why does manual state 300ml for tour and 350ml for sport? I don't see the difference in the forks.

And another. what weight oil do you folks reccomend.

Thanks

[DAVID THOMPSON]

in checkng my rt125 you have to take the fork legs off and dump them out
as there is no drain in the bottom
i got lazy last summer and took off the battery and gas tank and just turned
the whole bike up side down with a shop crane

[dthemic]

Now, really Dave. Don't make fun of me:)

Seriously, I want to know if anything bad happens if I remove the bolt that runs straight up through the bottom of the fork.

[keithcross]

Your idea should work fine, providing the top nut isnt attached to teh damper and spring, like they are on teh Baggi.
ou might want to change the oil 2 or 3 times in quick sucession though, to make sure all the crud that has built up over the years is out.

Keith

[DAVID THOMPSON]

not trying to PULL YOUR LEG the rt125 fork has no drain in the lower leg
at least on the one i own

probably a good idea as it is just one more place to have a leak if it does

ar dave

[pwillikers]

Yes, removing the allen bolt in the bottom of the slider will work just fine - it just takes a long time to drain because of all the nooks inside the forks where the oil can puddle. Remove the bolts and let it drain all night. Measure the quantity of fluid that comes out. Remember, Leave the fork caps in place when you remove the bolts - the spring tension holds the damper rod from spinning so you can successfully remove the allen bolts without the damper rod spinning inside the fork. Replace the drain bolts, remove the caps and springs and fill to 5.5" below the top of the tube with the springs removed and the slider fully compressed. Work the sliders up and down to ensure you've gotten all the air out. I use 20wt oil and it's to light. You might try 30wt.

Chronicle your experience when you're done.

[kman.45]

You might just find removing and taking apart the forks is the only way to go. You won't get the crud, bits of wear material, etc etc. out of the forks if you don't. There is no filter to capture material. You won't be able to inspect the bushings, seals, and lower part of fork leg that takes all the wear.

I am in the middle of changing the bushing, seals, and oil in the Baggi, with only 11K km. I've had bikes with 10x the mileage and never had an oil seal leak either (the problem that resulted in replacing all internal parts). I've not seen so much gunk in such low mileage oil before either.

Forks are not complicated. Take off the top cap which might be under slight spring tension if a conventional fork. Before you do though, break the bottom bolt free (need the spring tension and such to help with that, always a hassle if you try and do it with top part disassembled). As in the Baggi and other cartridge type forks, everything between the bottom bolt and top cap is captured and comes out in one big piece (see fork thread in 660c section). With conventional fork, the cap is free and then the spring is free to be pulled out too. Dump the oil out (check for black debris which would likely be bushings) rinse, pump, rinse, etc. If the oil is pretty clean with no excessive particles your bushing and seals are likely just fine, so just clean and fill. Fill to correct level, see manual, other areas of website, etc. Always fill for to a level, not by volume.

[dthemic]

Hello Folks,

Thanks for the replys. I think I now have a grasp of the pros and cons of both methods.

Since this is going to be the first time the fork oil has been replaced I think I will remove the forks and do the dump and flush.

Maybe the next time the other method when I know how old the fluid is.

Now, as to refill. I have come across some conflicting specs.
The owners manual: 300 ml for tour 220mm upper edge to fluid
350 ml for sport 220mm upper edge to fluid
SAE 10 for both

The parts manual shows no difference (that I saw) between sport and tour fork parts. So why different fliud amounts?

I have found reference on the board to both 300ml and 350ml as well as 160mm. and 139mm(5.5") from top edge to fluid, spring removed,shock collapsed. Weight 7.5, 10, 12.5, and up to 30. Wow, what am I missing?

I'm looking for best set up for 180 lb fairly agressive old street rider. Bike's got stock springs I got no cash to upgrade.

So I decided to remove and flush the forks. Now, what and how much do I put back in?

[kman.45]

Now, as to refill. I have come across some conflicting specs.
The owners manual: 300 ml for tour 220mm upper edge to fluid
350 ml for sport 220mm upper edge to fluid
SAE 10 for both

The parts manual shows no difference (that I saw) between sport and tour fork parts. So why different fliud amounts?

I'm looking for best set up for 180 lb fairly agressive old street rider. Bike's got stock springs I got no cash to upgrade.

So I decided to remove and flush the forks. Now, what and how much do I put back in?

perhaps the legs are slightly longer for one model? Either way you get to setup the forks how you want. I don't know the adjustablility of your bike's fork, but based on how you liked the ride of it stock, base your new oil around that. It will only be a guide as shock oil weights don't seem to be as consistent as say motor oil. Either way, at least now that you'll have some new oil in there you can remove and replace as much as you like, change levels etc. just by taking off top cap.

Get a few feet of vinyl hose and a decent sized syringe. Or get a Mity-Vac type bleeder. You can use the hose to remove all or part of the fluid to set levels, change weights, etc. If you want 100mm from the top of the fork leg, then measure 100mm on your tubing, mark it, insert tube, and suck out fluid until you hit that level. Want a bit more damping if you put in 10 weight? remove some, replace with 20 wt? All a big guessing game really. I would be quite suspect of 30 weight oil though, talk about excessive damping??