Topic: Front Forks: Air Assist

[Greggo]

I have a set of fork top bolts that convert the forks to air shocks for my K4 project...should I use 'em? 

If anyone has used these on their CB, I'd really like to hear your thoughts.  I have no idea what psi range to shoot for either if I do install them.

[lrutt]

Are you planning on taking the springs out completely and ONLY running air?

or just air assist?

Most systems I've ever seen were only air assist.

[Greggo]

Are you planning on taking the springs out completely and ONLY running air?

or just air assist?

Most systems I've ever seen were only air assist.

The springs stay in, it's just air replacing the oil.  EDIT: The oil stays in...

[RevDoc]

I know nothing about the forks on a K4 but the '82 CB750 Custom I just got is stock with air fittings. They require ATF in the forks with 12-16psi as well. I would check with someone knowledgeable about those forks to make sure the seals would be able to take air pressure as well as the oil. They might not have been engineered to handle the additional pressure.

[Powderman]

I have never seen a set that eliminates the oil. They are used normally at 5-10psi to "assist" in dampening. I would suspect that if you removed the oil completely the pressure needed to dampen would not be contained by the fork seals. Leaky fork seals are an issue with air assist caps even holding the 5-10psi. I just don't see air going through the valving the same way the oil would.
Where did you see that these eliminate the oil?

[Greggo]

I have never seen a set that eliminates the oil. They are used normally at 5-10psi to "assist" in dampening. I would suspect that if you removed the oil completely the pressure needed to dampen would not be contained by the fork seals. Leaky fork seals are an issue with air assist caps even holding the 5-10psi. I just don't see air going through the valving the same way the oil would.
Where did you see that these eliminate the oil?

This is why I pose these questions here.  What you see in those pictures is all I have, and I didn't see that they replace the oil...I'd just assumed that. 

Thank you for the info.  Since it doesn't require removing the fluid, I think I will just give them a shot and see how I like it. 

Have you used these before Powderman? 

[Powderman]

I have never seen a set that eliminates the oil. They are used normally at 5-10psi to "assist" in dampening. I would suspect that if you removed the oil completely the pressure needed to dampen would not be contained by the fork seals. Leaky fork seals are an issue with air assist caps even holding the 5-10psi. I just don't see air going through the valving the same way the oil would.
Where did you see that these eliminate the oil?

This is why I pose these questions here.  What you see in those pictures is all I have, and I didn't see that they replace the oil...I'd just assumed that. 

Thank you for the info.  Since it doesn't require removing the fluid, I think I will just give them a shot and see how I like it. 

Have you used these before Powderman? 

No I haven't needed them. They are used normally for heavier riders that need that little extra dampening without having to change oil weights or levels.

[strynboen]

the fluid passing thrugh pistons drilled holes calibrates damping in fork..so leave oil inside...the springs can be asisted by the air..but a kombinasion vith thinner oil and air kombinasion is the idea of this mod..cbx prolink use air forks..think 1-1,5 bar is normal..but thek by others..im can be vrong,on that..

[Greggo]

I have never seen a set that eliminates the oil. They are used normally at 5-10psi to "assist" in dampening. I would suspect that if you removed the oil completely the pressure needed to dampen would not be contained by the fork seals. Leaky fork seals are an issue with air assist caps even holding the 5-10psi. I just don't see air going through the valving the same way the oil would.
Where did you see that these eliminate the oil?

This is why I pose these questions here.  What you see in those pictures is all I have, and I didn't see that they replace the oil...I'd just assumed that. 

Thank you for the info.  Since it doesn't require removing the fluid, I think I will just give them a shot and see how I like it. 

Have you used these before Powderman? 

No I haven't needed them. They are used normally for heavier riders that need that little extra dampening without having to change oil weights or levels.

Gotcha.  I'm about 170, so I probably don't fit into that category.  The forks for this bike already have good Honda fluid in them, so I guess I'll see how they feel as is first...I can always jack up the front end and swap these on later.

Thanks for the info guys!

[przjohn]

The air pressure acts like a stiffer spring and will leak out the seals unless they are in perfect condition. If the front end is sprung good for your weight you are better off without them.

[SOHC4 Cafe Racer Fan]

Greggo,

You may check out the 650 forums since the CB650 use air assist, as well.

[seanbarney41]

Greggo, I had those same caps on a 550.  I only used them because they were on a parts bike and looked cleaner than the pitted chrome stockers.  Without air, your forks will perform exactly as stock.  Add 5-10 psi and they will feel just a little bit firmer.  The pressure would only last for about a week, though, with fresh oem fork seals and very clean stanchions.  Don't use a standard air compressor or tire pump to inflate.  Too much, too fast and it will just blow past your seals.  Use a high quality hand pump with an accurate gauge, such as one designed for athletic equipment.  My shop mate just happened to have a really nice pump that was mc specific since he is an ex-Harley dealer mechanic and has all the slick tools.

[Stev-o]

Sounds like more hassle then it worth, Greggo.

[SOHC4 Cafe Racer Fan]

Sounds like more hassle then it worth, Greggo.

I'd have to agree based on that assessment.

[seanbarney41]

Yeah, the only reason to use them is cause they are there, but as said, they are no different than stock until you add air.

[scottly]

My Seeley came with similar caps. I ditched the air fittings and threaded plugs into the holes. They are a bit lighter than the stock steel caps.

[SOHC4 Cafe Racer Fan]

You could also ditch them for a set of billet aluminum preload adjusters from either TTR400 or Rob/Voxonda. 

[seanbarney41]

You could also ditch them for a set of billet aluminum preload adjusters from either TTR400 or Rob/Voxonda. 

or spend a few hours experimenting with some chunks of pvc pipe and get the exact same results and actually learn something instead spending money

[scottly]

Why would I want to ditch the vintage billet aluminum caps???

[SOHC4 Cafe Racer Fan]

You could also ditch them for a set of billet aluminum preload adjusters from either TTR400 or Rob/Voxonda. 

or spend a few hours experimenting with some chunks of pvc pipe and get the exact same results and actually learn something instead spending money

Sean is absolutely right.  You can get a preload from PVC.  It won't be as readily adjustable but you can always experiment with different length PVC inserts.  I guess that means I have a spending problem! 

[Stev-o]

You could also ditch them for a set of billet aluminum preload adjusters from either TTR400 or Rob/Voxonda. 

or spend a few hours experimenting with some chunks of pvc pipe and get the exact same results and actually learn something instead spending money

Sean is absolutely right.  You can get a preload from PVC. 

My Progressive rings came with PVC spacers for preload, I opted not to use them.

[seanbarney41]

That's ok Steve-O.  You simply chose not to take advantage of a simple, diy, front end tuning parameter.  I have not screwed around with pre-load much myself.  My bikes all handle better than I can ride anyway...mostly...