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Replacing air shock fluid on GL1500. Why not

11026 Views 22 Replies 11 Participants Last post by  limpy45
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After my recent bout of stupidity in which I had to replace both shocks, I have noticed what an amazinglysmooth ride I have since I got everything back together. I am sure part of the reason is new parts but I don't think that explains everything. The replacement air shock I got was minus an unknown amount of fluid so I ended up draining the rest and refilling it. Now I started thinking about it. It has fluid just like the forks, rear end, brakes and clutch. I know that a lot of folks change those fluids on a regular basis. Well the air shock has fluid that is regularly exposed to outside air when adjusting so it stands to reason that it should also get contaminated after a while and lose it's damping ability. I know that there is dessicant in the compressor that should filter out contaminants but even still, I imagine that it will still go bad after a while. Why shouldn't this be changed on a regular basis too?

I discovered that it really isn't that hard to do. It does need to be removed from the bike to do it as it needs to be turned upside down to drain it. Right saddlebag needs to come off. The air fitting needs to be removed using a 14mm socket and then the top and bottom shock bolt need to be removed. After that, turn it upside down and pump it a few times but be careful because it will spray out. After pumping a few times, it should be pretty much drained. Next turn it right side up and slip something through the bottom mounting hole so you can stand on it and keep it up right. I used a long screwdriver. At this point I found one of the cone shaped fittings from my mityvac kit that was cone shaped on one side and flat on the other. I believe I used the second one from

the top on the right. The backside fit inside the opening for the air fitting pretty well by winding it in. I then attached a length of clear hose to it. Next I used a syringe that had a cone shape on the end that fit tightly into the other end of the clear hose. It was similar to this one and can be found at pet supply places for a couple bucks:

I bought a bottle of Honda SS-7 suspension fluid. I pulled the plunger of the syringe out and filled it to 60cc=60ml of fluid holding my finger over the end, stuck the plunger back in and turned the syringe upside down. Leaving the shock collapsed, I then put the syringe into the other end of the clear plastic tube. While holding the syringe in one hand, I pulled up on the shock while standing the screwdriver. This created a vacuum and while squeezing the syringe, the fluid got sucked right into the shock. After the fluid went in, I pulled the plunger out to release the vacuum then pulled the syring off to fill it again. I collapsed the shock again and repeated the above step a second time. I did this one more (third time) but only filled with 20cc=20ml of fluid. The capacity of the shock is 140cc=140ml of fluid. This last time, I didn't collapse the shock. I did however pull the plunger out on the syringe and put the plunger back in squeezing one last time to force all the fluid out of the hose. I then brought the shock back over to the bike and installed the top and bottom bolts. FYI, they only need to be torqued to 17 ft lbs so this is just slightly more than snug. I then attached the air fitting making sure that there was still the o-rings on either side of the banjo fitting.The air fitting only needs 4 ft lbs so basically just snug.

This procedure was no more difficult than changing out the fork oil or anything else, I may just to add it to things to periodically change.
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Great info Pwhoever............. gonna give that low-down to the schitz-it and flip that flubber up against the wall.
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Very good point. I just rebuilt my 2 rear air suspension shocks ('82 GL1100 Interstate). The left one was leaking oil. I purchased the parts from Dillion Brothers. I ordered all rubber part plus bushings. I followed the Honda service manual and used ATF to refill. What a difference the ride is now! Forget progressives. I noted that the old oil was "rancid" and milky. That indicated water contamination. However, it is very difficult to drain oil. Also '82s did not have compressor. Just old fashion hand pump.
thanks for the information on this. I just did mine, and when I drained the old stuff, there was only about 90ml in the shock. when filling, I put in 140ml. (now I have to see how that affects the ride!)
As for getting the ATF into the shock, I bought a cheap ketchup sqeeze bottle from the dollar store, measured out 140ml and put it in the bottle, stuck the nipple into the fitting, and extended the shock. I had to extend it slowly, and it just sucked all the fluid into the shock. Worked slick!
Thats a great idea about the ketchup bottle. It would probably be the easiest way to do it. Thanks...
That should have been on my to do list 2 winters ago when i put a new rear tire on. Also a new u-joint boot to replace the 6yr old one that just developed an inch long split. Black silicone works great until the new one gets installed.
I just changed mine, didn't have 140 ml in it, maybe 90 ml. Color was good. Can't wait to see the difference (tomorrow). Is there any damping action on the right shock, or is it just air spring all the way ?

In any event, raising the level of oil changed the effective mechanical spring rate at any pressure, and new fluid most likely lowered the sliding friction, raising the compliance some.

Result-less tendency to hobby horse from front to rear (have progressives in front). Bike is actually smoother over some types of road irregularities. Secondary roads with multiple RR tracks at X-ing, better control, less harsh. Since there is more fluid now (145 cc called out in 2000 year SM), the air volume is less, so compression stroke results in a higher restore force, sort of similar to a higher compression engine due to smaller combustion chamber volume.
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Help Cant get oil back in shock

1986 changing oil in rear air shocks

Oil drained out over night.. but cannot for the life of me get any back in.

Dont have a press so I could compress the shock. Have to experiment.

Would have like to try the compress method but off the bike.. didnt have anything handy to do this. I used a cone shaped rubber fitting as mentioned above. Short piece of plastic tubing... then slowly (and I mean slowly) I fed the 10 plus oz in.
This has just became my next "Must do" when I work on the wing again. If I have problems compressing it, I will try a ratchet strap to compress it. If that doesn't work, 2 dozen donuts the the guys in the fleet shop at work will get it done.

Ride Safe,
Here is my theory. I am thinking the springs in the shock have to have it extended all the way since it is off the bike. (this is off a gl1200 so not sure if it is the same or not.)

I am thinking I will need to compress the shock against those springs with a homemade tool or maybe a hydralic jack. close it up maybe half.. apply oil, let it expand thus sucking in the oil and repeat.

Stop me if I am missing something.

You are right. The GL1500 has no coil inside. I haven't changed the fluid in my 1100 for the same reason. On the 1500, super simple.
air cyl seal

Decided to rebuild the air cyl. I didn't quite have it sitting right when i blew the air into it to get the seal out and see which way the new one goes back in. oops!!

Books says lip side goes toward case which would be left side i think in the pic. Looks like the protruding end with the visible spring(left side in the pic) goes into the cyl first. The OD of that side is SMALLER also and would start easier into the case according to common sense but not sure if i have enough of that anymore.

There is a spring on right side also but burried down in there.

When i looked at it before disassembly it sure seemed like the protruding spring side was toward the outside, but my eyes might be seeing things. Has never been apart as far as i know.

Anybody remember for sure?
Search doesn't work anymore on this forum like it used to. Type in air cylinder and it gives me hundreds of threads for anything but that.



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I forget from the last one but would be inclined from your pic to install the left side of it facing outside.

The business end of a seal to hold something back would be the concave side (air/fluid side). The outer left part of pic would be like a wiper seal to prevent foreign debris on piston from entering into shock. And the 3rd item would be the full shoulder of seal that would be sitting against the retainer/install ring.

That would be my best guess.
Thanks DriveRider for the input.

Looks like 2 lips on the right side close together and then a big gap to the left lip.
Funny how the left OD is smaller and would be easier to install that way.

I called a local place that sells seals and brgs. and he said usually the protruding lip with the more exposed spring goes toward the oil and pressure.

Wish i wouldn't have gotten in such a big hurry and bounced that sucker out of my pan up against the wall. Haste makes waste.
Everything was going too good up until that point.
Hold the guide bushing up to each side of seal for best fit, I think it will smash into the protruding end which would not seem correct.
Good memory.
I did notice that. It's just that the Honda manual confused me when it said to fit the lip toward the case which meant that end in first to me.
Time to go to my real job.
I stopped at a farm equipment place and asked them which way to put the seal and the service manager said the left side out he would think.

I remember someone saying they destroyed their keeper ring trying to get it out. I ordered 2 but didn't really need them.
To get the keeper ring out, you have to push down on the back up ring very hard with a screwdriver and work side to side and you will feel it move down. It only has to move enough to clear the keeper ring. I had a new keeper ring so I used it on the very end and didn't replace the other one buried down in there..

I made a spacer at work so i could put it on top of that thin lip of the back up ring. The hardest part was to get the seal started straight and keep it straight. Lube it up good first. The best way was just put a screwdriver on top of my spacer that was on top of the back up ring, than tap it with a hammer and worked my way side to side. Not really a pressed fit but just tight. Put a little oil into the cylinder so that when i applied 40-50psi of air the seal would move along with the back up ring all the way to the keeper ring and past like it was before. It wouldn't do that until i put maybe an ounce into the cylinder. I just wanted to make sure it was locked in before i installed it back on the bike.

Wasn't all that bad to do.
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Do GL1500 originally has 2 rear air shocks or is an extra? Mine has only 1. And when the one gone previously rear wheel was touching a mudguard. So was thinking what will I do on a journey away?
Is it softer bike with 2 air shocks?
Due to the number of hits and information provided by Mike and Steve within this thread it would be of benefit to include the Honda part # of air shock dust boot which fit all 1500's.

Boot #52611-MN5-003
to GL1500 Aspencade1995:
The GL1500 originally had one hydraulic shock with spring on the left side and one air cylinder with no spring on right side to adjust for load and ride height.

I guess you mean that you only have the shock on the left side and nothing on the right? You could get a used air cylinder to put back on the right if your shock is good yet on the left or get a pair of Progressive 416's(i believe is the number) and those are air adjustable shocks.
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