Zongshen 200GY-2: Fork Service at 41,922 Miles

[SpudRider]

I have now ridden over 100 miles with my new fork oil. I'm pleased to report the fork damping is now softer after installing the Valvoline MaxLife Dex/Merc ATF. My suspension is now riding better on pavement, as well as off road. Based upon these results, the next time I change fork oil I am tempted to choose an oil with a viscosity of 20 cSt.

Spud

[Weldangrind]

Thanks for the follow-up, Spud. Is there a cross-reference that we can wrap our heads around? For example, does 20 cSt roughly translate to 10W?

[SpudRider]

Originally Posted by Weldangrind

Thanks for the follow-up, Spud. Is there a cross-reference that we can wrap our heads around? For example, does 20 cSt roughly translate to 10W?

That's an excellent question, Weld.

Firstly, the 10W, 15W, oil weight designations from the sellers can't be trusted, since one vendor's 5W oil might have the same viscosity as another vendor's 10W oil. :roll: The following chart illustrates these discrepancies.

http://www.peterverdone.com/wiki/ind...spension_Fluid

Also, one shouldn't completely trust the chart, either, since the viscosity of a particular brand of oil might change. The only sure way to determine viscosity is to read the product data sheet (PDS) or the manufacturer's safety data sheet (MSDS) for each individual oil. For example, the Verdone chart lists the viscosity of Mobil1 Synthetic ATF as 34.0 with a viscosity index (VI) of 199.00. However, the PDS for this ATF at the Mobil website lists the viscosity as 36.3, with a VI of 176.

http://www.mobil.com/USA-English/Lub...hetic_ATF.aspx

I chose the Valvoline MaxLife Dex/Merc ATF for several reasons. First of all, it has the lowest viscosity of any ATF I researched.

http://www.valvoline.com/pdf/maxlife_atf.pdf

As an added bonus, this ATF had the lowest price. I bought the Valvoline ATF for $13.50/gallon at my local AutoZone store. Contrast this price with the cost of the "boutique fork oils."

http://www.autozone.com/autozone/acc...er=819367_0_0_

I changed the fork oil in three motorcycles this month, using the Valvoline MaxLife Dex/Merc ATF, and I still have over a quart of ATF left over. However, I did use Showa SS-7 Fork Oil for the inner cartridge of my CRF250X forks, since the valving is designed for an oil with a viscosity of 16 cSt.

Most of the Dexron VI ATFs also have a low viscosity around 30 cSt, which is very close to the Valvoline MaxLife Dex/Merc. However, none of them could match the price of the Valvoline.

Spud

[SpudRider]

ATF is excellent fork oil, and many of the "boutique fork oils" are either ATF, or hydraulic fluid. The two most important factors to consider when choosing a fork oil are viscosity, and the viscosity index (VI). The VI measures the ability of an oil to maintain its viscosity over a wide temperature range. Any fork oil with a VI over 100 will do an excellent job in a motorycycle fork, and all the ATFs I examined have a VI which easily exceeds 100.

ATF does an excellent job in the outer fork tube of even the most sophisticated, high-tech, twin chamber forks currently available. Some riders even use ATF for the inner chamber, and say it does an excellent job. However, the valving inside the inner chamber is designed for fork oil with a viscosity of 16 cSt. Since each inner chamber uses less than 200ml of fork oil, I splurged and bought a pint (16 ounces) of Showa SS-7 Fork Oil for the inner chambers of the forks on my CRF250X.

I put Valvoline MaxLife Dex/Merc in the the outer fork tubes of my CRF250X. I also used the Valvoline ATF to replace the fork oil in my Zong and my Honda XR650L.

Spud

[SpudRider]

As I reported earlier, the Mobil1 Synthetic ATF, with a viscosity of 36.3 cST, did a good job in my Zong's forks. However, I like the performance of the Valvoline MaxLife Dex/Merc ATF, with a viscosity of 28.2 cSt, even better. As an added bonus, the Valvoline ATF was much less expensive than the Mobil1 ATF.

However, since my Zongshen forks only require 225ml of fork oil, I will splurge next time, and experiment with a "boutique fork oil" with a viscosity of 20 cSt. I don't know of any ATF which has a viscosity lower than the 28.2 cSt of the Valvoline MaxLife Dex/Merc ATF.

Spud

[SpudRider]

Unless someone is racing, he will probably be content to use ATF for fork oil in even the most modern, twin-chamber forks. Besides the Valvoline MaxLife Dex/Merc, just about any Dexron VI ATF will do an excellent job. All of the Dexron VI ATFs are either a synthetic blend, or a pure synthetic oil. Also, most of the Dexron VI ATFs have a viscosity close to 30 cSt. In particular, the SuperTech Dexron VI ATF sold by WalMart for $4.37/quart would do a good job. However, the Valvoline MaxLife Dex/Merc is also a synthetic blend, and represents an even better value than the SuperTech Dexron VI ATF.

Spud

[SpudRider]

Looking at Verdone's chart, I would estimate fork oil falls roughly into the following classifications.

2.5W is about 10 cSt viscosity
5W is about 16 cSt viscosity
7.5W is about 28 cSt viscosity
10W is about 36 cSt viscosity

Et cetera.

Based on these rough estimates, I replaced the stock fork oil with 10W ATF (Mobil1 Synthetic ATF at 36 cST). I recently switched to 7.5W ATF (Valvoline MaxLife Dex/Merc at 28 cSt), and the damping is smoother. I think I will next experiment with 5W fork oil (20 cSt).

Spud

[bsskibum]

followed your spectacular guide..
my 250gs dove and was not a nice ride since i got her..
well I now know why...

[bsskibum]

crap...
i dont know why but i did 250mL instead of 280mL at least i figuered out i can just jack up the front end loosen the nuts on top and lift the tire a tad to unseat the top and add another 30mL hahah
i used dex 6 walmart supertech brand...
complete job was around 2hrs.. i am rather meticulous..
discovered a few more issues while i was poking and prodding around the front end...
oh ya also replaced both the calipers bolts with non-allen heads

[SpudRider]

Thank you for your kind words. You were wise to switch to hex head bolts for the brake caliper. Servicing the forks and brake caliper is much easier after replacing those bolts.

[fishman10]

So if i read this correct ,,there is no way to change the fork oil on a zong without removing the forks from the bike??

[SpudRider]

You might be able to loosen the bottom bolt slightly to change the fork oil, but I certainly wouldn't recommend that method. Removing the forks is not only the best way to change the fork oil, it is undoubtedly the easiest method as well.

[Pliskin]

Originally Posted by SpudRider

You might be able to loosen the bottom bolt slightly to change the fork oil, but I certainly wouldn't recommend that method.

You are right Spud it didn't work for me. It's best to remove forks it's not that hard.

[SpudRider]

Thanks for corroborating my testimony, Pliskin.



Indeed, it really is easiest to remove the forks. In addition, you most certainly do the best job of removing the old fork oil when you remove the forks.

[pete]

Originally Posted by SpudRider

You might be able to loosen the bottom bolt slightly to change the fork oil, but I certainly wouldn't recommend that method. Removing the forks is not only the best way to change the fork oil, it is undoubtedly the easiest method as well.

Remember the days when forks had 6mm drain bolts..




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