It seems odd that they would ask you to increase the viscosity of the oil. I always understood, with increased spring rate you would want less compression dampening and more rebound dampening. Obviously with fixed orifice forks you cannot alter the ratios between compression and rebound dampening (without a drill ). By increasing oil weight, you increase compression dampening.

Of course the real proof is in the ride! How does it feel to ride Bosley? Have you gone over any unexpected potholes?

Phil W at 115kg you are a big chap. The XT stock suspension is supposedly for a person 70-80kg (I assume without gear). I would say yes, you are grossly undersprung. There is no replacement for correct rate springs. That being said the normal solution for bottoming out forks is to raise the oil height (put more oil in). This causes the air spring (the air pocket above the oil at the top of the fork) to start at and increase at a higher rate. This stops the fork bottoming out. Although at 115kg, I think you really need some stiffer springs.

nop wrote:It seems odd that they would ask you to increase the viscosity of the oil.

"Read this:

http://www.peterverdone.com/wiki/index. ... sion_Fluid

Stock, the xt runs '10w'. Assuming Yamaha have kept their oil the same since the mid 80's this is 33.2cst(centistokes).

I have at no point run 15w oil.

The actual viscosity of fork oil changes across each brand. One brands 10W may be lighter than another brands 5w! There is no consistently whatsoever."

Do you read your own threads Nop

Rick

All the 'rumours' on the interwebs suggest that hyperpro 15w is well above 46cst@40deg. In fact I have read that hyperpro oil is rebranded putoline. putoline '15w' is 67.5cst@40deg. Yamaha 10W is 33.2cst.

So I am technically right, which is the best kind of right.

But you are also right. I should be more specific with the language I use.

nop wrote:Phil W at 115kg you are a big chap. The XT stock suspension is supposedly for a person 70-80kg (I assume without gear). I would say yes, you are grossly undersprung. .

OK rub it in

nop wrote:So I am technically right, which is the best kind of right.

Fair enough

Rick

It was supposed to be a joke

nop wrote:It was supposed to be a joke

& I took it as such

so was my reply

Rick

nop wrote: Of course the real proof is in the ride! How does it feel to ride Bosley? Have you gone over any unexpected potholes?

YES, whole CZECH REPUBLIC (who experienced it, never believe) is one big pothole so I bought a enduro...

I did the measurements, if the springs are tired (the original). And not in a good condition (according to the instructions on the Internet - was measured to decline without load (weight of the motorcycle only its own weight) and then even with the driver - a triangle) 80kg + wear a backpack shoes etc. = 85-85kg.
Then I invested in older spring stronger wire less thread, but was also tired. That's why I bought everything new. Tested including oil. Normally is soft as standart and copies the road, but if the pothole hardens. If the bike under load (rider) - not so low

nop wrote:...

There are aftermarket springs available from Hagon, Hyperpro and Wilburs with the following rates:

Make/Model Part number Rate
Hyperpro

XT600E (90-94) SP-YA06-SSA009 6-11 N/mm
XT600 (86-90) SP-YA06-SSA027 3.3-4.4 N/mm
XT600(3AJ) 88> SP-YA06-SSA010 5-11 N/mm

Wilburs
XT600 (85-90) 600-0099-00 4.1-5.9N/mm

These are all I have found so far. The rates came from asking the companies listed what the spring rates were. Hagon never got back to me.

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I have found that Progressive suspension sells two springs for the XT600s too. These springs can be found on ebay.com and other US sites.

1984-1989 XT600 Progressive Suspension Spring Part # 11-1141

20/30 lb/in = 3.5/5.25 N/mm

Length 571.5mm = 22.5in Diameter 34.8mm = 1.37in


1990 - onwards XT600E Progressive Suspension Spring Part # 11-1506

30/40 lb/in = 5.25/7 N/mm

Length 571.5mm = 22.5in Diameter 34mm = 1.35in

I have ordered the XT600e springs for my '86 XT600. The same Progressive spring for the XT600e is recommended for Honda XL600, Honda NX 650 Transalp BMW F650, DR650 & the KLR650. The Honda XL & the XT600 share similar wet weight as does the DR650. The other bikes are heavier. Which is good in my book as I am looking for something on the stiff end of the spectrum for the bike.

The first stage of the spring will be a similar spring to a HyperPro XT600e spring but the Progressive spring will be softer in the second stage. On an older XT600 the spring should stiffen things up proper on the front end. I wager nose dive will be not so much of an issue with a 5.25/7 N/mm spring rate.