Fork springs for 1986 g/s

[Damien]

My g/s is suffering from front end bounce on anything other than very smooth surfaces. Has anyone tried either the Motorworks progressive springs or those from Hyperpro?

I changed the fork oil last year but this has made only a tiny difference.

Any Info greatly appreciated.

 

[Rob Farmer]

The motorworks springs are shite, they deform and rub badly against the inside of the tube when you fit the plastic fork spring caps. if you don't fit the caps they haven't enough preload and the poorly finished ends gouge the ally top nuts.

The g/s forks are standard road bike forks from the era with a spacer in the bottom to make them sit higher. The fork springs are RS/rt springs so if you run the recommended 5w oil they will pogo. They work much better with a decent 7.5w oil in there.

Are you sure it's the forks causing the issue? More often than not it's the back end lacking preload/damping that gives the impression it's the forks.

 

[Damien]

I never thought of of that Rob. The original rear shock burst two years ago and I replaced it with a Wilbers. I am unsure if there is adjustment on the rear, I would doubt it. I will steer clear of the Motorworks springs, I might change the fork oil to see if it makes a difference, I only changed it last year but can't remember what I put in.

Thanks for the info, I will let you know how I get on.

 

[jimish]

It's worth overhauling the forks before you spend any money on new springs. It's easy enough to do if you follow the Haynes manual. Replace the damper wiper rings and fork seals as a matter of course. Measure the springs free lengths and replace with standard if neccessary. Just a good clean will make all the difference. Don't use anything less than 7W oil.


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[Rob Farmer]

I bought a new wilbers for my g/s it was a terrible thing and far too harsh, every bump was like being kicked up the arse. You may find the shocks putting all the emphases on the front end and needs to be softened a bit. The problem with the shock specialists is they set everything up as if it was for a sports bike which doesn't work for most bikes.

even if you bought the cheaper wilbers it should have preload adjustment on the spring and damper adjustment.

 

[Rob Farmer]

It's worth overhauling the forks before you spend any money on new springs. It's easy enough to do if you follow the Haynes manual. Replace the damper wiper rings and fork seals as a matter of course. Measure the springs free lengths and replace with standard if neccessary. Just a good clean will make all the difference. Don't use anything less than 7W oil.


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Are you thinking of the pre 81 forks when you mention damper rings?

 

[jimish]

Don't think so Rob.
I bought James Sherlocks part No 112649 when I did my 1981 G/S, looking back on the invoices.

 

[Beemerboff]

Poor fork action can be due to poor alignment too.

As Rob has already pointed out the forks are basically tarted up road forks, and the flat plate top triple just isn't up to any serious off road work, and can end up fatigued and twisted.

And it is pretty hard to assemble a worn set of forks in decent alignment, as you depend on the worn sliders for alignment.

Simplest way is to get a billet top triple - the low cost San Jose BMW one fits with a bit of trimming and the indicators flipped and switched, and it will make a decent difference on worn forks.

Some decent suspension fluid helps to - Bel Ray and Maxima make a 7 1/2 wt HVI Synthetic suspension fluid which works better than any Dino fork oil you can buy, and it will last twice as long so it ends up cheaper too.

 

[Mick13]

I've got WP springs, with 7,5W oil, that's OK on my G/S

 

[Rob Farmer]

I've switched to yamalube for most of the fluids for my airheads. They do a 7.5w along with a variety of other weights - it's best to stick to one manufacturer as the viscosities vary wildly between manufacturers of oils. The big plus with yam oil is you can get it at any yamaha dealer in Europe, the prices are good and the oil good quality. They also do bevel and gearbox gl5 oils.