Suspension feels like a bouncy castle!

So I was riding to work this morning, nothing out of the ordinary similar speeds, same roads (smooth and no lot holes) same riding habit...

I was about 15 miles into my 18 mile journey when it happened, the front end just sort of 'gave up' and it went very very soft and very bouncy..

My first though was oil leak from a broken seal or something but there are new seals fitted a month or so ago and there is no sign of any oil on the bike or the forks/calipers/wheel.

There was no crack or sound when the suspension 'went' it just happened.. It wasn't a pot hole just going around a corner and it stopped working!

I need some help diagnosing the fault please! At the moment I can't get the forks off I will have to wait till I'm down the garage tomorrow I'm just trying to sus out whats going on and if its going to be an expensive repair.

The bike is a K4 SV650S however the front end is a K4 GSXR1000 (USD forks) and they've done circa 20,000 miles. New seals approx 1000 miles ago.

TIA,

George

Here's a guess.
When the seals were replaced, they didn't put enough oil in the forks. There was enough to cover the valves for 1000 miles, then enough left through normal use (oil gets wiped onto the fork pistons every time they go up and down, and it doesn't come back).
Once the valves were no longer covered by oil, you lost suspension control.
Like I said, just a guess.

I'm going to go look in a manual for similar forks. I can't think of anything they could have done while changing oil that would allow something to fall off after 1000 miles, but I'm old, sometimes my brain won't tall me what I want to know...

Would that cause a sudden loss of suspension or would it be gradual as the oil level decreases?

Well, it whould be a gradual deterioration. It seems highly unlikely that both forks would run out of oil at the same time, and even one side working would still give you some (reduced) damping. I once ran some USD forks over 20,000 miles without servicing them. They didn't have much oil left in them, and the damping was definitely deteriorating, but it was going away gradually and noticeably.

I can't think of anything that would explain a sudden total loss.

Do those GSXR forks have compression in one leg and rebound in the other? Probably not. Is the compression valve(s?) internal or bolted onto the outside at the bottom?
If the valve shim stack came loose from the damping rod, that would give you a sudden loss- but there's no reason to mess with the shim stacks when changing fork seals and oil... and both of them falling off at the same time?
Have the forks been re-valved? The factory valve installation usually involves staking or swagging on the nuts that hold the shim stacks on. They just won't come loose.

At the least, you need to get inside far enough to check the oil levels.

It's a strange problem, and I'm interested in learning what you find out.

[yorkie_chris]

Something come loose. Rebound rod from cap maybe.

Originally Posted by yorkie_chris

Something come loose. Rebound rod from cap maybe.

That would be pretty obvious wouldn't it?

Did you use a torque wrench when you reassembled them?

Just a wild guess but are the damper bolts in the bottom of the fork still in there and no leakage?

I'm just about to build my SRAD USD forks up from my first ever strip down. Its a bit daunting!

[yorkie_chris]

Originally Posted by wideguy

That would be pretty obvious wouldn't it?

Well fork can over-extend if this is case cos top out is internal to cartridge. This would be very obvious if both forks... not so much if one fork.

Either way no point discussing it really... pull forks in bits and see what's gone amiss.

Originally Posted by yorkie_chris

Well fork can over-extend if this is case cos top out is internal to cartridge. This would be very obvious if both forks... not so much if one fork.

Either way no point discussing it really... pull forks in bits and see what's gone amiss.

I meant visually obvious, as in the rods were no longer sticking up through the fork caps, or were moving up and down in the fork caps as the suspension moved.

[yorkie_chris]

You can't see rod in fork cap... that is adjuster screw connected to rebound needle.

If not connected then piston and rod just flops down to full compressed position and stays there. No oil is moving when suspension moves.