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  #1  
Old 29 Apr 2007
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Stiffer forks xt600e

Hi guys

I have my forks out at the minute while my bike ('03 xt600e) undergoes a bit of a makeover. One thing that i hate about the bike is the poor forks. The dive at the slightest touch of the front brake. I want to try to stiffen them up firstly, without buying new springs. Im gonna use heavier oil, and someone has mentioned fitting a spacer under the spring. Anyone tried this? What sort of size spacer should i be looking to fit? I can make any size up in work as i have access to a lathe.

Thanks
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  #2  
Old 29 Apr 2007
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xt forks

Hi,
I have just bought an xte 2003 to replace my dr350 and also have noticed how soft the front springs are compared to the dr which has multi adjustable suspension. the amount of front dive is very noticeable when braking, i plan to replace with hagon progressive wound springs as these are supposed to stiffen the more they are compressed. i have heard of people cutting a small bit of pipe the same diameter of the fork springs and inserting this into the fork leg in front of the spring, although how long to cut the spacer is another question.
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  #3  
Old 30 Apr 2007
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Using a spacer above the spring will increase the preload and stop the spring from compressing as much when you get on the bike. I've done it on other bikes but I think it's best to get some progressive springs. I started with trying 1 washer width and progressed to 2 washers. It doesn't take much.

Try this link. It's more street oriented but it has some good stuff "Bikesetup"
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  #4  
Old 30 Apr 2007
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I just replaced the standard spacers with tube 15mm longer than standard.
This is for carrying weight, 20L feul tank, panniers etc.
Took a visit to a local metal fabricators and got them to cut some pipe for me ... total cost £4

Completely understand buying progressive springs if the springs you have are shot but if all you want is a stiffer front end use spacers and save yourself some hard earned cash
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  #5  
Old 30 Apr 2007
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If you sit on the bike with it carrying the full load the forks should sag by about 1/3 of the total available travel

1) If they are sagging by 1/3 or less and you only want to stop dive, then thicker fork oil may be the best way forward. Also, more oil than standard will decrease the air volume and provide a greater air-spring effect that will come into play as the forks dive and compress the air in the forks

2) If they sag more, then the spacers are a good cheap solution to raise the ride hieght without altering the spring rate (the stiffness of the spring)


3) if you are handy, you could drill and thread the fork top-nuts to take some air valves. You can make these by stripping the valve from an old inner tube, cutting the rubber off until you are back to the brass and then soldering the tube into a brass pipe fitting for which you need to obtain the right tap in order to thread the hole you drill in the fork nut. You can then put say 5psi in each leg to give you some air spring assistance. Don't put too much in though as you may pop the fork seals
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  #6  
Old 30 Apr 2007
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Regarding the last reply and air valves, would the fork tops from a 3AJ screw into the Es forks, might be easier than drilling and fitting valve.
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  #7  
Old 1 May 2007
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The standard fork springs on the XT600E are already progressive. They're are just too soft for road use.

Increasing the preload with spacers is an option but this will reduce the amount of travel available.

Hagon do harder springs and people have said good things about them although you are giving yourself a harder ride off road with less softer travel to take out the little bumps.

If your trip is going to be mainly on road then I say go for the stiffer hagons and maybe also experement with spacers.

If its just dive you dont like, then just try spacers first.

Nylon tubing (available from plumbers merchants, b&q etc) is perfect for the job. Easy to cut and very tough.

I posted a thread about this and got some answers from people who have fitted the hagons (cost £85 i think)
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  #8  
Old 1 May 2007
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Thumbs up

Thanks for the replies fellas. I have the forks stripped for an oil change and getting the lower fork legs powdercoated too. Turns out the previous owner must have changed 1 fork seal as 1 fork had clean oil and the other was substantially dirtier. No noing if there was even the same ammount of oil in both. I'll knock up a couple various thickness spacers maybe 10 and 15mm and do some experimenting when i get them built back up again. They are so quick and easy to work on compared to the upside downers on my CRF. Only tool i had to make to split them was a long reach 27mm hex tool to hold the damper rod and allow me to undo the bolt in the bottom.
Oh yeah i don't ride the xt off road at all. It's mainly the braking 'dive' im trying to improve

thanks
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  #9  
Old 2 May 2007
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Have to disagree with tedmagnum. Adding spacers won't reduce the amount of travel unless they are so big the springs become coilbound.
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  #10  
Old 2 May 2007
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Quote:
Originally Posted by rickg View Post
Have to disagree with tedmagnum. Adding spacers won't reduce the amount of travel unless they are so big the springs become coilbound.
When you preload the springs you are reducing the amount of available travel.

Imagine you had a spring 10" long. If you compress (preload) the spring by 2" then you have 8" of compression available instead of 10"

Admitedly, if that 2" was very soft, you wont miss it anyway but it can take out the "rumble"
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  #11  
Old 3 May 2007
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Sorry if I sound harsh but this thread contains a lot from half truths via quarter truths to utter rubbish.

Let's start with some facts. The XT 600 front end was always on the soft side. While it works for very petite riders and normal riding a big bloke / blokesse, two up or hard riding will quickly put the front suspension to and past its limits.

Note that most luggage does not increase the load on your front end significally. Tank mounted stuff and low slung tool tubes are obvious exceptions.

The soft front dives deep on the brakes. Problems are the front end bottoming out on rough roads as well as the steering getting a bit nervous. Besides loss of comfort and control the bottoming front suspension causes excessive wear on wheel and steering head bearings.

How to fix front end problems?

With spacers: One of the simplest and cheapest ways. The spacer preloads the spring but does not make the spring harder.
Spacers will work if the fork only shows a bit too much static sag but does not dive excessively and does not bottom out.
Problem: Increasing the preload will stress the spring and it might set (shrink in free length). If you shorten the free length of a spring while keeping all other parameters identical your spring rate decreases = the spring softens.
Also as mentioned earlier you are moving towards the spring becoming coilbound.
Preload spacers should only be applied very carefully. Depending on the free length of the spring I would not increase the preload of a fork spring by more than 10mm to 15mm.

With more oil:
By slightly increasing the oil level you decrease the size of the air chamber. As the fork compresses the internal air pressure increases more sharply giving the fork more progression. (The fork gets harder the more it compresses)
This fixes a fork which rides fine but bottoms out occasionally when riding hard.
Problem: This works only within limits. It causes more wear on the fork oil seals and will pop them if you overdo things.

With air preload:
Helps to fix a fork that rides fine but shows too much static sag.
Problems as above.

More oil and some air presssure can fix a slightly soft front end perfectly and very cheaply. The downside is a lot of wear on the fork oil seals.

These three fixes will only work to a very limited extent!

With thicker oil:
This is utter rubbish. Using thicker oil makes your damping harder. It does not change the spring rate of the suspension system at all. The harder damping will make your ride uncomfortable by hydraulically locking your suspension. It will cost precision around corners and it will bottom out you front end on hard braking and top it out on hard acceleration on rough roads.
Many bikes especially DS come with hard front end damping from the factory to improve high speed stability on tarmac. The BMW F650 GS and Dakar are a good example. Heavier fork oil leaves you in a mess.

For any seriously soft front suspension like a fork that rides with too much static sag, dives harshly under braking and bottoms out frequently there is only one fix:
Replace the fork springs!
In the case of an XT 600 this is very well invested money.
Keep in mind that a prematurely worn steering head bearing will probably cost you the same to get fixed save the hassle.

And Tedmagnum: The travel of the fork is usually determined by the way the inner fork tube can move between the damper piston and the bottom of the outer tube.
Only putting the preload spacer into the bottom of the inner tube underneath the damper piston will preload the spring and reduce the suspension travel. (example DR650SE on low setting)
Putting the preload spacer on top of the fork spring will only preload the spring without affecting the travel. (example DR650SE on high setting)
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Old 3 May 2007
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Im also not a fan of using thicker oil, but..... Increasing the weight gives the "effect" of stiffer springs by slowing the rate of compression so the fork may not bottom out on a certain bump. Admitedly this does have consequences with with a non adjustable fork. I cant agree this is utter rubbish as its a tried and tested method and used widely on road and competition. Of course this is a bike by bike case and I havnt tried this on an XT yet to comment.

People are also forgetting that the XT springs are already progressive, although I agree they are still too soft for road riding.
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  #13  
Old 3 May 2007
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It is a good idea to know where you are starting from before you make any changes.
Measure the static sag and loaded sag.
Spring rate, if it is progressive find the range.
Oil weight.
With that info you start to make changes ideally one thing at a time.

If bottoming out is the problem stronger springs would be the sure fire way to stop that. You would need to adjust the damping to suit. I prefer linear springs as it is easier to sort the damping. You can add adjustable damping to the forks with a Race Tech emulator.
I have a project at the moment, to improve the forks on my Transalp. It is work in progress but the results so far have been impressive. You can find some info at Improving Front Suspension - Honda Trail Bike Forums
Steve
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  #14  
Old 3 May 2007
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I also forgot to add..

If you put harder springs in without adjusting the damping you can get quite a pogo stick effect.

The standard damping is for the standard spring rate. The only way to change the damping on the XT is to use differenet weight oils.

I havnt fitted stiffer springs yet but when I do ill post up my findings.
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  #15  
Old 4 May 2007
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I fitted wp springs and valvoline 5-20w oil,
Its great.
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