DRM 400

[YSS]

By the looks still  a 1 and two 0 to many for your needs , and probaly to expensive too  .   Happy websurfing Leith.

[oldfart]

Ok I will bite
                  Rm 250( 79)  38mm forks are starting point                                          way too light
                                                                   spring length  = 580mm
                                                                   windings        =  59
                                                                   gauge           =    4.22mm
                                                             spring OD             =  30.45
                                                                      Id              =  20.73
                                                                   Travel            =235mm

[YSS]

That does not bite

I can offer 29 OD  540 freelenght   4.8N   if you just need one

[cloggy]

Thanks 77 I've bookmarked that. Seeing as how KTMs used zzochi 38s as well then one of their springs may work
OF I have 16.5" 4.5" stroke shocks on a standard swingarm at present. It seems to be a slight rising rate 2 to 1 ratio so I have just over 9" of rear suspension.
I can sit on the bike with my feet flat on the ground, and the kickstart is still low enough

[brent j]

With regard to springs for this, I'd pick the weight to be about the same as my XT500.
Any settings I use, and I'm happy to pass on, were what worked well at that time. I am continually looking for improvements. Oldfart, ask Asasin what he thought of my front suspension, and it's been improved again.

I used XR250 Honda springs, both main and secondary as they were available and free. They work out to be about 25lb/in or about 4.5N, Walter???
What sort of price would you be looking at for making the springs you mentioned in your other post? I think you mentioned 4.5N. This seems to work well enough to equip all my 500's

I've tried a third spring (23lb/in) with what turned out to be too much preload but now run just the two XR springs with only 2-3mm of preload. This is just enough to stop them rattling and no more.
THE HEAVIER SPRING WITH LITTLE OR NO PRELOAD GIVES A MUCH SMOOTHER RIDE! the bike sits higher, is far more responsive to bumps and bottoms a lot less.

I recently changed my fork oil from 10wt to 15wt as the bike was bouncing back a bit to much on jumps and what an improvement in overall ride. You don't realise how much of what you feel through the bars is not actually bumps on the ground but the wheel slamming back down too fast.

I like to ride modern bikes to give me something to aim for.
If you want to play with suspension I'd suggest getting seveal bottles of fork oil, different weights, and be prepared to throw it all away trying different settings.
Spend a day removing and adjusting PD valves trying different fork oil heights and weights.
AND, don't be disapointed if a whole day seems to have been wasted and you see no improvements. Remember the experts became experts very, very slowly.

Brent

[YSS]

Thanks for your input Brent , yes 4.5 N or there abouts should work fine for up to 100 kg rider in combination with the PD valves,  Do you think the same spring could also fit the  XT ?  Would 550mm  freelenght be enough ?  What max OD can we make them ?  What stroke is required ?
If we make a batch , they would sell individually for $179.00  if you or a club buy a few , we can talk.

[oldfart]

Walter & Brent , hang on a minute ... The XR springs I have tried are 4.95m thick .  So are there Two guages available in the XR series  4.9mm and 4.5mm as the 4.9 is way too stiff .

Spent the afternoon trying different combos .

1 = Xr250 twin spring 4.9mm       too harsh not using all available travel .... possible spring bind
2 = Rm 400 spring ( 540 long) 4.22mm  with top out spring  ( Brent issue ) ..... smoother ride ... bottoms out 
3 = Rm 250 spring ( 580 llong ) 4.22 and top out spring  improvement over above ... still too soft

Todays conclusion    try same windings as Rm springs ( 59 ) but need heavier wire possible 4.5 mm

Bye the way I have a XT 500 ,  DR 400 are much lighter 

[cloggy]

When dirt bike "white brothered" a DR back in 1980 they ended up with much the same weight as they started due to stuff like the forks weighing more.Around 290lbs fully gassed was about it.
 TTs came in at 274.5lbs with a us gallon of gas and a 43.6% bias on the front wheel.
Both the DR engine and frame weigh pretty much the same as TT , stuff like the rear wheel assembly is likely to be heavier than TT/XT
Standard a DR is much better balanced than a TT, 4 years was a long time back then.
Race Tech has a neat chart that gives a ball park figure for fork springs. It seems to correlate with what you and others have incrementally  decided upon OF.

[brent j]

Oldfart

I think my XR main springs are 4.5mm so my apologies there. If I get a chance I’ll pull out my springs and measure the main and secondary springs this weekend.
The RM springs you gave specs for in a previous post have a rate of about 16.4lb/in. You need about 25lb/in.
Race-Tech suggests 25lb/in springs for the front of an XT/TT or racing, Works performance say 23, I tend to agree with Race-Tech.
Try 25lb and if it’s still too stiff I’d be looking at your damping

Check out
http://www.pontiacracing.net/js_coil_spring_rate.htm
and save the calculator. You can then work out what rate springs you have.

Use this
http://www.proshocks.com/calcs/2spgrate.htm
if you use two or more springs

The XR springs I have are just on 25lb/in using both springs. The main spring alone is about 34lb/in and impossible to ride. Adding more springs (coils) reduces the rate. I originally used the top out spring in mine to reduce the 25lb to 23lb as it felt stiff on small bumps but this was caused by using too much preload. When I went up to 25lb and no preload the stiffness went away and it also bottomed less.

My bike weighs in at 126kg (277lb) with a full tank of fuel so I’d guess your DR is pretty close.

My current setup is
PE175 fork legs with IT465 damper rods (to get 9” travel)
25lb/in springs, 2mm preload
15wt oil at about 140mm from the top, not sure here as I measure mine at full extension with springs in place.
Race-Tech cartridge emulators with 64lb/in springs with 2 turns preload for less high speed comp.

I have a set of YSS PD valves and as soon as I get time I will fit them start playing.
This set up is for now, if I find an improvement next time out it will change. I’ve changed the set up twice since Conondale and I expect a few more changes through the year.

The right spring will hold the bike up, sag 6-10% with the weight of the bike and 25-30% when you sit on it. After that it’s all down to damping.
My two cents worth anyway

Brent

[YSS]

Brent , have you made those jets for the PD Valves ?

[YSS]

Back to the old question , should we make a universal spring to suit ? What demand is there? Or does somebody already offer that size and rate ?

[cloggy]

There doesn't appear to be anything available in the UK, though I may change my mind after the upcoming show. But seriously how many people are modding stuff?
If you wanted to market them you could get an article in VMX and UKs Classic Dirt bike, that would shift a few sets
Also the UK's yamaha thumper website would be worth a pitch. that site's so good XT fanatics check it from around the globe
Every year a few people do the Heroes Legend Paris Dakar on XT500s. This modern event was set up specifically for XT500s
Their website would be worth a punt.
Lastly Kedo have now got an outlet in USA and this german website is the first port of call for a lot of the Heroes guys, so it would be worth contacting them to see if they'd be interested in shifting a few sets, that is if you aren't already tied into another european distributor

[cloggy]

Thing is old stock springs turn up at under £50 a set in the UK so folks are still going to scrabble around for alternatives.
Brent
If my Maico springs do turn out to be [as expected] too hard for anything other than a desert going petrol bowser; I was thinking of cutting  my spare wimpy RM springs down to the length of the spacer and softening the  overall spring rate that way. There's a few inches  of spacer so I thought that might help, or am I being thick?
My forks are  off an 81 Rm 125 and are  have over 10" of travel
I've raised the stanchions over an "  and the bike is OK above walking speeds. I know I could steepen the head angle more, as when I got it it was running the max rear shock length and standard 7 to 8" forks, and there wasn't a hint of instability.
There's an article by Super Hunky that goes into a lot of detail about cutting and shutting springs, though in the context of stiffening , rather than softening, suspension                                                 

[YSS]

What is the link to that TT site ?

[cloggy]

http://www.yamaha-xt500.com/phpBB/portal.php        is the UK site