88 GSXR250 Forks?

[Pumba]

Ok, I am playing around with a new frount end on the bucket from a 88 GSXR250 (I think), all good I am starting to get a bit more familiar with the internal workings of these magical devices.

Anyway, these forks have an aire valve in the top cap that I presume from my playing around is to pressureise the forks with compressed air therefore altering the preload pressure? Can someone confirm this?

Also if my suspesions are correct what pressures should I look at starting at with these? or I could just keep the compresser running till I blow a fork seal and then back it off a bit

[speedpro]

I always thought the air caps were a stop-gap till you got the right springs. Start at 0psi and maybe go to a maximum of 0psi and see how that goes. Do your sag measurements, make spacers, have a look at the compression damping holes. If there's 4 then get rid of 1 or 2 and try it. Try different weight fork oil. Different springs or cut down the existing ones and install longer spacers. Have you got the forks mounted yet? Sometimes they are a bit long for buckets and you end up with quite a bit above the top triple clamp which always looked a bit dangerous to me. A bit of time with the 9" grinder and a cutoff disc will shorten them up in no time. Then you just need to get a circlip groove cut inside and a little cap with an o-ring and she's all good. Easy.

[speedpro]

The other thing people do is add 20psi which stops it bottoming out, but at the price of having it topped out at all other times you aren't hard on the brakes. Eh!

[Robert Taylor]

The other thing people do is add 20psi which stops it bottoming out, but at the price of having it topped out at all other times you aren't hard on the brakes. Eh!

And at the price of a LOT more seal friction. Fit appropriate springs and ditch the idea of running above 1 bar pressure at full extension. It always was a silly idea, even though air is free.

[Pumba]

Thanks guys, yea I know fitting appropriate springs or cutting the existing ones to get the correct sag would be a far better idea, but to do this requires a) more money or b) more tools, which equals more money and neither is going to hapen at the moment.

Might have to have a bit of a play with the dampening holes in the rod though.

It always was a silly idea, even though air is free.

From a suspension lamans point of veiw there seemed to be quite a bit of merit the idea (its not the first time my logic as gotten me into trouble though, I mean shit racing buckets was ment to save me money what a joke). Would you mind expanding on why it is a silly idea? Is it because of the increased pressure on the seals decreasing the life? or another reason?

[Robert Taylor]

Thanks guys, yea I know fitting appropriate springs or cutting the existing ones to get the correct sag would be a far better idea, but to do this requires a) more money or b) more tools, which equals more money and neither is going to hapen at the moment.

Might have to have a bit of a play with the dampening holes in the rod though.



From a suspension lamans point of veiw there seemed to be quite a bit of merit the idea (its not the first time my logic as gotten me into trouble though, I mean shit racing buckets was ment to save me money what a joke). Would you mind expanding on why it is a silly idea? Is it because of the increased pressure on the seals decreasing the life? or another reason?

Increased pressure on the fork seal lips increases seal drag / friction enormously. Dont undersetimate it, it makes fork response lethargic and takes away sidegrip.

[speedpro]

Increased pressure . . . . . takes away sidegrip.

And you want side grip. Think about tossing it into the sweeper, full throttle, knee down, dragging a peg, and finding your side grip is back in the pits.

[F5 Dave]

. . Start at 0psi and maybe go to a maximum of 0psi and see how that goes. . .

Nice answer.

So have you run the forks yet? or not? What is the issue? I would have thought that a heavier bike like a 250 would have reasonable springs to start with when put on a bucket, but you can never tell till you try. Start with the right amount of oil & set the preload so the sag is right (this is the free bit so can't moan about it being too expensive), cut a longer spacer until you have it right, you can borrow a hacksaw yeah? Practise until you get it square, like proper square.

Then are they too soft? Springs only option, can't get around that.

[Kickaha]

I put the same front end in my bucket (GN150) with stock oil level and grade and 0 air pressure and it works very well

One day I mighte even get around to doing the sag but it worked so well I didn't bother making any changes to them

[Pumba]

So have you run the forks yet? or not? What is the issue? I would have thought that a heavier bike like a 250 would have reasonable springs to start with when put on a bucket, but you can never tell till you try.

I havent run them yet, the reason I asked to confirm if my thoughts on the set up and how the forks operated with the air valve was correct or not. As it turns out my thinking was flawed.

Will know more about how the feel and preform when I get them on the bike, shit they have got to be better than the RG150 front end I have been running with a blown fork seel