G/S front forks

[solidstate100]

Hi guys

Might be a bit of a stupid question but can anyone think why one of my fork springs sits a bit higher in one fork leg (the right side compression one) then the other? Both springs are recent Hyperpro, and the same length. The old springs as far as I recall were the same lenght also, but totally shot so any discrepacies could have been hidden.

Both sides have 25mm preload spacers, the rebound side the fork cap goes on as normal, ie with a small amount of pressure, the compression side its a real bear to get on, and to my mind has far to much preload (and is reducing my sag, which is why I am trying to sort it out) but my intial concern is what could the reason be for the spring to sit higher than the other one?

 

[oldnfat]

Hi, I replaced my knackered old springs with hyper pro last year. Springs are the same length with the same amount of tension on both sides replacing the end caps. The only thing I can think of....other than the valve becoming dislodged it that you haven't drained all the oil out. Have you left the drain screws out when fitting the springs?

Also I was advised to shave 5mm from the spacers and use 10 weight oil on the compression side and 7.5 on the rebound. I didn't do this as concerned that I would screw up the front end. Tried a pal of mines who has done this and have to say the suspension was better damped and took away some of the harshness. Have applied th same and has worked well.

 

[Beemerboff]

G/S forks are the same both sides, unless you have fitted GS forks to your G/S
It seems to me that if the spring wont go in there has to be something stopping it - try shining a torch down the tube to see if it is visible, or take the leg off and turn it upside down and see what comes out.
If you have GS forks there are a few bits which could be either be missing or perhaps both be in one side - one of the POs might have botched thing up!
Dont worry too much about rebound damping - if your spring rates are correct you need very little - I have it at the lowest possible setting on my GS/HPN forks

 

[solidstate100]

Apprciate the responses so far, thanks guys.

Oldnfat - Definatly not oil /oil retention releted - the spring hits a "hard stop" - you can physically hear it bottoming out and become solid. Apppreciate the tips on oils weights etc tho - as it happens I am running as you suggest BUT the other way round - but as the preload is all wrong I will revisit this when I sort out the spring seating/preload.

Beemerboff - I was hoping you would respond as your previous post on suspension etc have been informative and spot on. They are stock OEM G/S forks.I read some schematics last night and pretty much came to the same conclusion - I am hoping that there may be an errant spacer or somesuch in there from a PO's attempts (the springs I removed were progressives so someone has been in there before) and had decided that I will whip the leg off and flip it and see what if anything transpires. I am rather hoping it will be simple like an old OEM spring seat guide or a dropped socket or something! I will update as soon as.

 

[solidstate100]

Soooo....... not an errant spacer left in the tube. I flipped the leg, and out popped the top piston, followed by a short spring, both of which had come unscrewed/off the top of the damper rod. The piston was sitting on top of the damper rod, hence the spring sitting higher in the tube than the other side. Sadly, it seems this might be another PO's attemps at some sort of repair as with the leg flipped over a mass of orange instant gasket becomes apparant. I stripped the leg out (circlip out bottom plug out) and the amounf of sealant in there plus a completely bent over O ring seem to point to some sort of botched repair in the past. WHY DO PEOPLE DO THIS!!

I have no idea why the damper rod has become unscrewed, maybe the action of the crap spring on the piston over time, but have managed to button it back together for now but it leaks like a bastard (hence the PO's orange sealant trick I suppose) so further remedial work is needed. Looking at the schemematics etc I am not actually convinced that I have the full set of bits in there either......

Work in progress......

 

[solidstate100]

Slight up date.

Having managed to get out for a ride I can say that now the damper rod is screwed back togother and things seem to be operating in loosely the fasion they should be, the front forks are now .............shockingly awful, appalling, the worst by a massive amount that I have EVER ridden. Something is not right, and at the moment I suspect the hyperpro springs are WAY WAY to stiff.They were bought from motorworks as being for a G/S which may well be true , but only if you weigh maybe 50st. I may put the original springs back in as I cant bear the jarring crashing ride. oil is 7.5 weight compression side and 10 weight rebound side, but I seriously doubt changing that round or making both the same at either weight is going to get me in the ball park.

More work needed it seems

 

[Kenny]

A G/S should have 220cc in each leg usually 5 but 7.5 is max.

Only the GS para with Marzocchi forks has a different grade for each leg. Not much help. Fork springs in right way up?
No spacers of any kind IIRC ( although with standard springs I usually put in a 10mm spacer at the top).

Not much can go wrong with G/S forks...very basic indeed.....must surely be the wrong springs sent.

 

[solidstate100]

Thanks Kenny.

At the moment 20mm preload spacers in there, I will remove them and drop the oil weight to 7.5 both legs see what happens. Is it OK to run the springs directly against the fork cap? Also didnt think it made any difference what way up the springs were - thay have the tighter windings at the top at the moment (per Hyperpro's instructions IIRC).

 

[Kenny]

Tighter windings usually go at the top. Take out the spacers.

 

[Beemerboff]

My only experience with Hyperpro was along time ago with a kit for a VFR , which was also made for a 50 stone rider and made the bike virtually unridable.

FWIW I have since discovered that the technology does not exist to make a spring with a progressive rate to any meaningful degree, so I am always a little wary of dealing with anyone who sells one, or of taking advice from someone who claims great things from them.

Rob Farmer actually tested some so called progressive set ups and posted the results, and they were even worse than mine, he found absolutely no progressiveness whatsoever , but since then he has had the sense to keep quite - no point in telling someone what they are not going to believe.

But it is easy to be fooled initially - I just put a set of softer springs on my F650 and like most folks put the fork caps on with the forks at full extension, which in effect half's the air gap when the bike is at rider sag, and the forks felt great like that for a few days until the excess air leaked out.
Air is actually naturally progressive, and reducing the volume makes the forks feel progressive - the second tube on some Moto GP forks is actually a air chamber, for this very reason.
Now I have to work out what oil level is going to give me the same feel ------.
FWIW most modern forks have an air bleed screw which lets you remove the excess pressure before you take the bike out for a ride.

 

[chrisshrops]

My Hyperpro springs in my rat were way to hard I contacted Bas at hyperpro directly ,and he was super helpful he send out some spring for another bike which work a treat ,utterly transformed my forks .
I would contact hyperpro and see what they say .
Anyone thinking of getting some of there springs agin go direct and chat with them first they may wel be able to advise on a better set up

 

[solidstate100]

Cheers chaps. I have removed the (20mm) preload spacers and equalised the oil weights across both legs at 7.5wt and ...............hmmmm, well, things are a bit better actually. Is it sorted? No not really. I still think the spring rate is far to stiff, but things are a little less crashy and violent and at least it is just about borderline tolerable at the moment (as long as I keep the 32 litre tank nice and full that is....) for the first time I actually get a tiny bit of fork rise as I accelerate so it looks like I am back "in the stroke" a bit better, but I would like to contact Hyperpro for some feedback/advice. Chrisshops can you let me have Bas's email address please (PM if you dont want to broadcast) - much appreciated.

Still a way to go I feel, but at least I can keep my filings in my head at the moment.

 

[Bubb]

springs

I put Hyperpro progressive springs in my ST when I rebuilt it, as the originals were 30 years old, had put up with the weight of an RT fairing and were knackered.

followed hyperpro's instructions, used the oil that came with the springs (not sure of the weight.) and if anything, the forks are slightly too soft. They track the road great, but dive like a premiership footballer in the box when the brakes are applied. Im thinking of slightly heavier oil, or just another 20cc or so of the same weight in each fork...... might try the more oil first, then heavier weight if they still dive too much.

I know the G/S and ST forks are different in construction, but hope this helps.

Bubb

 

[Beemerboff]

According to the Racetech site if you have the correct weight of springs you will get a reasonable amount of dive under brakes - little or no dive is the easiest test for over stiff springs.
Their suggestion is a bit more suspension fluid to decrease the air gap, so it seems you are on the right lines, but you will probably need more than 20 cc.

 

[solidstate100]

Soooooo...........the plot thickens............I have been digging out the paperwork old box etc in preperation to contact Hyperpro so I have all the ref nos etc to hand. And.....when I ordered my Hyperpro kit the bike was not in PD trim so out of the choice available I asked for the standard ie non PD kit. The kit had to be ordered in from Hyperpro, it arrived 3 weeks later, I fitted it. More fool me for not checking the box then - in infintessinally small print not possible to read without a magnifying glass it says "R80 G/S PD". The order paperwork confirms NON PD ordered......Hmmmm

That was just over a year ago. Now, somehwat coincedentally, the bike IS in PD trim so I would like to think that I have "brought to bike to the springs", I am assuming that the difference in Non PD to PD is no more than a slightly stiffer rate to compensate for the 32 litre tank. Interestingly (again in the unreadable print) fork oil level is specified at 150MM with the sliders fully compressed (note MM not cc or ml) so using 220cc as I have is maybe way out (but I bet it isnt!).

All that said we are still where we are - I still feel the rate is to stiff but strangley (didnt mention this before, forgot) the rider sag now seems quite a lot - sits down like a sportsbike (well, relativly anyway) with approx 60mm of rider sag (difficult to check properly as am flying solo in the man cave/workshop at the mo) I have had to shorten the sidestand (easy as its a Migstand) and getting it on the centrestand with full tank is a right struggle now......

The only time this bike feels acceptable is when it is fully laden then it is tolerable but as the fuel runs down back we go to the crashy stiffness.......hmmmm

Maybe I will try reduced oil levels (thus leaving a bigger more progressive air gap) or at least use Hyperpros set up method to see if that helps, will still contact Hyperpro for some feedback as well.

 

[Kenny]

Your chasing your tail. Whether PD or not doesn't matter...if you have a R80G/S then I'd simply buy replacement ( I know..more cost ) R80g/s forks>

Maybe HyperPro manufacture these forks for a R100GSPD..which is a completely different beast.

 

[Beemerboff]

HPN supply two different length spacers with their insert kit for the GS , short ones for the stock bike and 10mm longer ones for the bikes with the larger PD tank.
The short ones give a little bit under 60 mm rider sag, which works fine for me with the #80 /450 lb spring in the Ohlns shock.