Fork springs - what's the normal level of length loss over time?

[Canis G.]

I am just doing up the forks on my sons GN250. The manual says the minimum length of the springs (before they need replacement) should be 610mm, the ones I pulled are around the 490mm mark - that's 80% of the minimum length. Is this normal for the springs to have reduced so much in length?

Ta.

[pete376403]

25 years of carrying fat buggers around - yeah they'll sag a bit.
Ginnys being what they are, maintenance scores fairly low. You're probably the first person to see those springs since they were installed at the factory.

[F5 Dave]

not to say that suzuki didn't change the spring supplier to save money. GNs have the most horrible fork dive due to soft front forks & cheapo valving. Makes the front prone to locking in emergency brake situation. Stiffer springs are about the only thing you could do without spending more than the bike is worth. Adding preload will not help the rate. Fitting lower bars helps with ridiculous riding position aiding control, did that to an old girlfriends one back in the day.

[Robert Taylor]

F5 Dave is right, there is no brake dive resistance ( and there is no valving ) But there likely will have been several spec variations over such a long model run. Normally length change is minimal with fork springs that are high quality, and even if the length changes the rate doesnt change.

If they had shortened that much the forks would be bottomed at rest!

Given that some of the later GN250s were fully made in China then the metallurgy would have been similiar to chipboard, so anythings possible with the rubbish that comes out of that country.

[Canis G.]

Yeah I thought it seemed a tad excessive from 610mm + to 490mm! Figuring it must have been a spec change. Yeah they are a funny wee bike I just want to get it to ride a better for him (not worth doing the silk purse from a sow's ear thing) so was going to sort out the wear and tear, up the oil weight to try and get a tad more damping going on, put the forks up through the trees to reduce the rake a tad and put some lower bars on. If it shows some promise I might try and find some better rear shocks - the stock ones are pogo sticks.

[Canis G.]

This GN is an 86 and seems to be made in Japan - I don't know if that means anything for the metal quality in the springs LOL. Any way put it all back together today (with the same springs) using 15W oil in the forks and sticking about 30mm of stanchion up through the top triple clamp. IMHO it has improved the ride quite markedly, front is a lot smoother and more stable over bumps and the steering is a bit more responsive without losing any tracking stability. Worked for me anyway.

[F5 Dave]

watch ground clearance, they don't have much to start with

[Canis G.]

Thanks for that Dave. It often seems to be the way, sort one thing then end up working on the next problem in the chain LOL. I ended up putting 15W oil in the forks and stuck 30mm of fork up through the clamps and it seems to have worked a treat (on this bike anyway) the forks soak up the bumps an awful lot better than they did (which is important around Chch at the moment LOL) and the steering is more nimble but at any conering angle approaching exciting the sides of my boots are starting to drag on the deck. Ah well, a bit more experimenting to do here.

[F5 Dave]

yeah from memory I don't think the pegs fold, so they will unhinge you if you hit a bump mid corner or lean too far.

[Canis G.]

The pegs fold, but I hate having no room left for dealing with any unexpected corner issues LOL.