I have just coverted my fork caps on my 1989 CB1 400 into air fork tops useing two new short valves i got off ebay for 99p. I run the forks with 14psi in them and find this is perfect for me giving a good ride on all surfaces and good cornering in the twisty"s with no loss of air in the last few weeks . So a cheap easy to do mod well worthwhile

It's a bit 80's but in theory should be spot on for increasing the spring rate. And I bet two air valves and a bit of PTFE tape is cheaper than new Hagon springs.

It's very definitely a better idea than just using thicker oil.

Only thing it could / probably will do is give the fork seals a hard time, you may end up replacing them more frequently than otherwise. ISTR back in the 80's air forks were run at 0-8psi to increase spring rate according to rider weight.

If I wanted tougher springs on a tight budget, I'd look at something like this...

http://www.ebay.co.uk/itm/HONDA-ST1100- ... 5d3aaccc8d
http://www.ebay.co.uk/itm/Honda-CBR600- ... 4d0971a840

ie, springs of the same diameter (I haven't checked that) from either a heavier bike with similarly soft forks, or a similar weight but sportier bike. Springs aren't model or make specific. You might need new spacer tubes is all.

I have had several bikes with air assisted forks HONDA"S and YAMAHA"S with a range of recomended pressures to run. My YAMAHA VIRAGO 1100 is best at 18psi and as for giving the seal"s a hard time the air pressure actually make"s the seals work better and i have stopped a seal leaking once by putting in a couple more pounds psi in. I also find a little air works well with standard fork springs and i have had bikes that i have used thicker oil in more preload and also progressive springs so i have tried them all but i was just pointing out i had improved my forks which have o rings on the caps so no ptfe needed cheaply and easy with this simply mod all the best rick. Also i must add never use an airline to add air just a bike pump or syringe.