1982 GS850G Fork Level Question (Yes, I searched!)

[Guest]

While changing fork seals last night, I encountered a problem regarding proper fork oil levels on this bike.

Background: This 850G has the air forks with the single schrader valve on the left side fork, which connects to the right fork with an interconnecting hose. There are no schrader valves on the top fork caps. During normal operation, the air/oil is transferred between the tube forks tubes by way of a single hole in the fork tube approximately 8" from the top of each fork tube, and a bracket assembly incorporated into the lower fork clamps, with a channel the matches up with the hole on each fork tube. This system is NOT connected to the brakes, and these are NOT anti-dive forks.

Also, I have Sonic Springs installed, and no cartridge emulators.


That being said, every maintenance manual I can locate specifies fork oil levels of either 5.5" (forks off the bike, measured from the top, springs/spacers out, fully compressed) or a volume of 8.5 OZ. As noted above, the air holes on each fork tube are 8" from the top of the fork tube, and a fluid level specified a full 2.5" above the hole. Needless to say, it is impossible to fill the forks with the Suzuki-specified levels without oil leaking profusely from the obvious air holes. Adding 8.5 OZ of fluid yields the same result.

What is the correct fork oil level for this particular bike?

The solution we came up with last night was to fully reinstall the forks on the bike, and add fluid to the empty fork tubes one at a time using the volume method of 8.5 OZ. The problem with this method is that any overflow above the air hole would drain into the other fork, thereby leaving potentially different levels between the two sides (even after I cycled the front end up and down repeatedly to work any air to the top), as well as not being able to properly measure the fork levels, given that the measurements listed must be with tubes level and fully compressed.


I have not yet found a clear answer anywhere. Sonic's website suggested the factory level. The forums have plenty of threads with air valves on tops of the forks, not the single on the side. I have found mentions of similar setups, like in the older Concourse (that the measurement should be made tubes extended due to the air holes?) but I am looking for a specified level for this bike.

Any thoughts, gents?

[Steve]

It only takes the placement of one finger over the hole to keep the fluid in.

Spring out, fork collapsed, hole blocked, 6" from the top.

I will usually over-fill with oil (10w, by the way), then use my vacuum pump with a zip-tie 6" from the end of the hose. Just stick it in the fork tube, turn on the pump, it stops drawing fluid when it gets to 6". Extend the tubes, install the spring and preload spacer, install the cap. Repeat with other tube. Remove whatever you had plugging the hole, install the forks in the bike.

Here is another tip that is useful when installing the top cap: in your case, it would help to do this BEFORE installing the oil.
Turn the cap into the fork tube one or two threads, just enough to hold it. While pulling gently on the cap, turn the fork tube to unthread it from the cap. Do this slowly. When the cap finally comes off, note where the Schrader valve was pointing on the tube. Use a Sharpie marker or a piece of tape to note that location. Now, when you are pushing against the fork spring while trying to engage the cap, you will know exactly where the threads will start to engage, making that part much easier.

.

[Live2fly06]

Thanks for the useful and prompt reply! I wasn't sure if it was as simple as putting a finger over the hole, or if I was missing an addendum to the manual for models with air forks for this procedure.

My original plan was to use my Motion Pro tool to set the levels, but the vacuum pump/zip tie is a good idea as well.

And I did use 10w oil ��

Cheers!

[mmattockx]

My 1100E forks will dribble oil out the air valving hole as well. I put a piece of tape over the hole to set the level with the tubes collapsed (while held vertical in a bench vise), then extended the forks and installed the spring, spacer and cap and carefully installed the fork legs back into the triples without laying them down or tipping them enough to leak oil out of the air hole after the tape was removed.


Mark