Topic: air inside forks?

[xsmooth69x]

i found this cb550k1 and the PO looks like he did a lot of cross country riding with the wind shield thing and saddle bags and front foot pegs....

anyways on top of each fork there is a blue top fork screw but it has an air stem on it. i pushed the inner air presure stem in and it defiantly released some air.

what is the point of this? should i take them off and put them on my bike?

i rebuilt my forks and used 20w bell oil. would i have to take out the oil if i use these?

they look cool 

[Spanner 1]

Well if they look cool then you must have 'em !!! Just a 'mod' you can do/not do.... go ahead, just don't put more than 1 lb. of air in there IMO.....and don't take out any oil either . Kind of a gimmick on forks that were not designed for air.......but have you seen the clear 'see thru' carb bowls, wow, now there's something to have   

[xsmooth69x]

so they arnt functional at all 

i want clear carb bowls!!!!!!

[dave500]

we used to have them on early dirt bikes to actually let built up pressure out from time to time!

[xsmooth69x]

so is there any functionality on the cb550? or did this dude just put them on for fun?

[dave500]

sometimes anything"trick"must be so much better,why not go one better and use a tee piece so both forks get the same pressure,chicks dig tee pieces!

[trueblue]

I don't know if this means anything but the '81 650 had air assist forks on it and the service manual says to inflate them to 10-16psi

[coma13]

Hondaman on here has recommended adding shrader valves to the fork caps specifically to enable air-assit. I was thinking of doing it on mine when I rebuild them.

[Kong]

Of course they have an effect.  A good rule to keep in mind is that if you change something it will act differently.  There is already an air column inside the fork, it is a very big part of how the suspension works, and if you change the pressure of that slug of air it will definitely change your ride.   The air that is in there now is compressed as the fork compresses and like any gas it will resist compression and in so doing will act as a spring; receiving and releasing energy as the air column contracts and extends.   Any air you add will act as a stronger spring  too and it will also act as a progressive rate spring (them more you compress the gas the more difficult it will be to compress further) - even if you have single rate springs in the bike right now.

By the way, I believe some of the 4-stroke Kawasaki twins (500 or so cc street bikes) from the 70's or early 80's had air valves in their fork caps and may have had air shocks in the rear too.

[xsmooth69x]

so should i get them and try them out?

[wingman1946]

It was an improvement put on the later Honda motorcycles. Some people add the air input valves to gain more adjustment capability. When Honda added them they connected the two valves together so the pressure would be equal in the two forks. The book does say 16 lbs max but I run 20lbs and have done so in several bikes. Most all of the Goldwings have air assist forks with their own on board compressor.

[xsmooth69x]

so does more air make the bike preform better?

like through twisties and stuff

[wingman1946]

I think most people have their own ideas about what is better performance. Myself I don't like anything to be overly soft or spongy feeling when I am enjoying the twisties. I also don't like to feel like my backside is hitting a board either. All that to say it is an option to give more choices.

[TwoTired]

Air pressure in the old fork tubes helps as an anti dive feature during heavy breaking and increases load capacity somewhat.
You only run 3-4 pounds max in these, unless you like frequent seal replacement or like to see them leaking.

They fell out of favor because the compression of air creates heat, which makes the air expand and the pressure increases even more.  Each time the fork compresses, the air gets compressed, too. So, if you do a lot of heavy braking as in the twisties or road racing, air pressure changes, effect the handling, as in changing the front rear weight distribution.  Then balancing tire traction near limits becomes harder to predict leading to a low or high side crash as one tire goes over the traction limit.
It is important to have a balance tube to equalize pressure between forks.  Running one with pressure and one without makes for some very unpredictable handling.

Every cafe racer should have those.  They look so cool when parked. And start lots of conversations.   

You don't actually have to put air pressure in there.

Cheers,

[xsmooth69x]

sweet totally going to get them great idea i just wont put air in them

ill run a spit ss line with one inlet so the air pressure is even between them.

with my clip ons they will be super noticeable

and i wont put air in them 

my new 1972 cb750 has them and an sw air suspension in the back to. the previous owner must have put them on...?

and they have them in the front too

[Mars]

Thanks for making this topic. I have some Goki ones on my CB400F that came from the PO, and I was kind of baffled and what to do with them. I do have to say, I hate them for one reason. Putting on clip-ons requires you unbolt them (won't slide through the holes in the triple tree). This means fighting them back on with the springs.