Changing Fork Oil

[1980GS850]

I need to take my forks off the bike to put on a fork trim cover piece that the previous owner had taken off. I thought I would turn take the caps off the forks, let them drain and refill with new fluid? Sound reasonable? I am not looking to any other work on the forks, would this method be acceptable? What type oil would go back in? thanks!

 

[GSXR7ED]

Interesting that fork questions keep coming up.

I believe I have 15W oil in mine but MrBill would have to confirm. It makes a big difference which type you use...but I want MrBill to explain.

Paging...MrBill....


Ed

 

[bonanzadave]

Well.....if that's all you want to do.....it couldn't hurt. I might flush them with some solvent then find the correct amount (service manual ?) and buy some fork specific oil. A qt will be enough for both forks. Get the exact same amount in each fork by checking the level with a stick I might also change the seals, bushings, and springs.....but its your Bike .

 

[RichDesmond]

I need to take my forks off the bike to put on a fork trim cover piece that the previous owner had taken off. I thought I would turn take the caps off the forks, let them drain and refill with new fluid? Sound reasonable? I am not looking to any other work on the forks, would this method be acceptable? What type oil would go back in? thanks!

That will work just fine. Pump them a few times while inverted to make sure all the old oil is out. If you want to do a bit more thorough job put a pint of so of ATF in each one and redo the pump and drain routine before refilling. If you're leaving the stock springs in use 10w fork oil and set the level to 100mm. Use the method outlined in step 10 here:

http://sonicsprings.com/catalog/damper_rod_forks_tech_article.php

to set the level.

PM me if you have any questions.

 

[hillsy]

Crack the fork caps loose before you take them out of the triples.

 

[Steve]

Crack the fork caps loose before you take them out of the triples.

And if you have (additional) air in the forks, be sure to bleed that off, or you will have some strange patterns on the far wall when you open the drain screw. :-\\\

Have you taken the forks off the bike yet? If not, measure your "sag". That is how much the bike will drop between full extension and when you sit on the bike. Ideally, that amount will be about 20-25% of total spring travel. Most of our bikes have about 4" of travel, so you want your "sag" to be between 3/4" and 1". If it is more than that, you should really consider new springs. Sonic Springs is a good choice, the owner of the company just responded to you a bit before I did.

GSXR7ED responded that you might want 15w oil. Many will choose that "to prevent diving when braking". Heavier oil will not prevent diving, it only slows it down. SPRINGS are what keep the front from diving, the oil just keeps them from bouncing. I took a tip from the suspension manager of a professional race team. His suggestion was to use the lightest-weight oil that will keep the wheel on the ground. I use 10w in all my bikes, with very comfortable, very controlled results.

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