Air Forks

[GS1100GZ]

Seems that I remember many years ago buying a kit that tied both forks together so that you had only one valve to add air. I don't remember who made it. Does anyone know if there is a kit like this still available? TIA.

 

[Guest]

Some GSes had tubes that tied the forks together. One that I know of was the 1100E.

An alternative is to replace your springs, which are probably worn out anyway, with stronger springs that will hold the weight without any additional air. Sonic Springs is one source. Progressive and Racetech are a couple more. Sonic has straight-rate springs that work very well. New springs and some fresh 10w oil changed my forks considerably.

 

[RichDesmond]

Yeah, replacing the springs is a far better solution. Adjustable air pressure sounds like a good idea, but...it's not.

 

[slayer61]

Seems that I remember many years ago buying a kit that tied both forks together so that you had only one valve to add air. I don't remember who made it. Does anyone know if there is a kit like this still available? TIA.

If you still insist on doing it, it can be done with hardware store parts. A couple of suitable pipe(brass or some such) fittings & some PTFE hose and a Schrader valve to fill with. Easy Peasy!

My rig in the '70s even had a small gauge included that you could watch climb when you applied the brakes!

 

[rphillips]

Yep, you're right, there sure was an after mkt. kit for this, I put one on a GS1000. But been too long, don't have a clue who may have made it. Mine was pretty crude, a brass tee with a Schrader valve & 2 short lines with couplings to screw on to each existing Schrader valve.

 

[Maddevill]

The 83-85 GS750/700 has air forks tied together with one valve. I plugged the holes in mine and put Sonic springs in.
Like previously said, air forks and brake activated anti-dive sound good but really don't work great.

Mad

 

[Grimly]

Not worth the bother, honestly.
A few years ago I was really taken with the idea of re-instating the air forks on the GS850, because I'd fitted a set of GS1000 forks with air adjustment.
I McGuyvered an air linkage just to see how well the idea would work, as I rapidly found that individual unlinked air forks weren't a great idea.
After several months of battling leakage issues I gave up with the idea. They worked well, but I could never get to the stage that I only had to check the forks once a week at most, unlike the air shocks on the rear, which quite happily go for a month before losing about four psi.
Anyway, I replaced the springs with new heavier duty progressives (can't get straight rate springs here for a sensible price) and DIYd a couple of pre-load devices on the top of the fork legs in imitation of the original GS850 adjusters.
This combination works bloody well, never have to re-adjust them once set and it's handling well, even with the fairing and everything else on it.

 

[GS1100GZ]

I had thought about piecing something together but didn't know if the caps were metric or not. I also was too lazy to try and get all the pieces rounded up. I was hoping for a kit. I spoke with Progressive and they said that it would be better to go with new springs and no air.

What weight oil is recommended for the forks? I have also heard to just use ATF. Expected load would run about 250 to 300 lbs.

 

[Grimly]

I used an old bottle of Spectro 10W fork oil that had been kicking around for years. It seems to be working fine.
Suzuki, back in the day, recommended a 50/50 mix of engine oil and ATF for forks.
On my XJ, I filled them with 5w40 engine oil.
Just about anything works, as long as it's not too far out there.

 

[Guest]

... but didn't know if the caps were metric or not.

You're kidding, right?

What weight oil is recommended for the forks? I have also heard to just use ATF. Expected load would run about 250 to 300 lbs.

Which ATF? They are not all the same viscosity, so you may as well use a new product that has only been available for 30-40 years or so, ... FORK OIL. With proper-strength springs and the proper amount of oil, 10w oil should be fine.

 

[GS1100GZ]

Being that it is a Japanese bike I would naturally assume that they were metric. You know what they say about ASSUME. I have no experience with air fittings so I didn't know if they made metric fittings. Why do you ask if I am kidding?

I heard to use ATF a long time ago.

Due to life and health issues it probably has been about 15 years since I was last active in motorcycles. I am having to get back up to speed.

 

[RichDesmond]

...I have no experience with air fittings so I didn't know if they made metric fittings. Why do you ask if I am kidding?

The USA, Myanmar and Liberia are the only countries in the world not on the metric system. Air fittings are not unknown in the other 192.

I heard to use ATF a long time ago...

ATF will work ok. The problem comes if you decide you want a little more damping, or a little less. At that point it's hard to figure out what to put in.
ATF also tends to be a little light if you've gone to better springs. If you're just doing touring/commuting and not riding very aggressively it shouldn't be too bad.
Real fork oil isn't that expensive though, unless the budget's really tight that's what I'd use.

 

[Grimly]

Being that it is a Japanese bike I would naturally assume that they were metric. You know what they say about ASSUME. .

You mean the fork caps themselves? Totally metric, but there's a gotcha. They're not all the same width even though they look it.
I had ASSUMED that I could use the GS850 adjustable caps on the 1000 forks, but no, they're wider by about a mm or so.
So, that started me on the merry dance of air forkery, and a total amount of forkery ensued...

 

[salty_monk]

I had one on my 1000G. Just more points to leak really.... Swap out the springs

 

[GS1100GZ]

What is the best way to get the fork oil level right? I have seen tools to do it with but this is the 1st and I'm pretty sure the last time that I will be doing this. I don't want to spend the money for a tool that I'll never use again. That's the story of my life. I have all kinds of tools that were only used once or twice. I have one of those fancy measuring cups with all kinds of level markings. I believe it was specifically made for motorcycles. Would that be close enough?

 

[RichDesmond]

What is the best way to get the fork oil level right? I have seen tools to do it with but this is the 1st and I'm pretty sure the last time that I will be doing this. I don't want to spend the money for a tool that I'll never use again. That's the story of my life. I have all kinds of tools that were only used once or twice. I have one of those fancy measuring cups with all kinds of level markings. I believe it was specifically made for motorcycles. Would that be close enough?

Here's the instructions from the Sonic Springs site:

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

It's important to set the level by measuring it directly, don't just pour in a measured volume.

That article outlines the turkey baster method, but you can just use ruler or tape measure too. Pour some oil in, stick the ruler in until it just touches the oil surface. Read the depth at the top of the fork tube. Add more oil if needed, or pour a little out if you overfilled.

FWIW I use the turkey baster. I bought a couple of the Motion Pro tools, they were handy but didn't last long.

Holler at me if you have any questions.

 

[salty_monk]

What is the best way to get the fork oil level right? I have seen tools to do it with but this is the 1st and I'm pretty sure the last time that I will be doing this. I don't want to spend the money for a tool that I'll never use again. That's the story of my life. I have all kinds of tools that were only used once or twice. I have one of those fancy measuring cups with all kinds of level markings. I believe it was specifically made for motorcycles. Would that be close enough?

Get the top off a spray bottle. Just your ordinary household cleaner/windex type thing. Cut the straw so that it's the right depth you need (measured from the bottom of the threaded collar). hold the plastic screw cap on top of the fork leg with the fork leg held straight. Pump the excess oil into a rag. Finished.....

Over the years I have quite a collection of spray bottle tops with straws cut marked to different lengths..... It's way easier than trying to measure it with a dipstick.

 

[GS1100GZ]

Thanks for the 2 tips. I'll have to try them. It's been so long since I have had to be resourceful. I have to start learning to think outside the box again.

 

[bwringer]

I made a fork oil level slurper out of some clear tubing, an old wire hanger, and a "Mix-Mizer" syringe. The syringe is sold in home and farm stores for the purpose of measuring 2-cycle oil for chainsaws and such.

The tubing gets zip-tied to a length of wire hanger artfully shaped to attach to the syringe at the top, then straightened to act as a splint for the tubing. Zip ties of assorted colors go at the correct depths. Dump in some fork oil, insert to the red zip tie for, say, 140mm, and sluuuuurp out the excess.

Oh, and you measure fork oil level with the springs OUT, and the forks all the way collapsed. Getting this wrong has caused problems for people before...

10W fork oil is my go-to.

 

[GS1100GZ]

I had originally thought about the syringe and tube method but was a little worried about how consistent that might be. I need to find some solid tubing. That would be more accurate. The baster sounds like the perfect idea. I have a baster in the garage but it's way too big. I need to hit the stores up before the holidays go by. I'm fighting other battles now so the springs will have to wait.