Modifying R90/6 front forks

[jagarra]

Been riding the BMW more lately, surprises me how much power the old girl has. Catch myself just going a bit too fast, when I hit a certain throttle position the bike just really takes off.
A couple of items are bothering me, the front forks and the side stand. The forks seem to go up and down smoothly, but when I am riding it, it just seems not to have much travel. That or they are near the bottom of the travel when I get on it. I weight 200, there seems to be more rear travel left than front if you get my drift. I was going through some round abouts yesterday and was banging the side stand on the pavement. Don't know if this is related to my concerns about the low riding front end or my riding. I didn't think I was over that far. The stand is firmly against the exhaust pipe, so it can't go up anymore.
Recently added new Race Tech kits ( springs and emulators) to my Connie, made a world of difference, has anyone installed these kits in their Airheads? Curious as to what my options are, could I just add more preload with a spacer, already using 15 wt oil.

thanks,

gg

[chasbmw]

Try a preload spacer first, if your fork springs are old, then replace them, the 90/s springs are a bit harder and work better with the closer fitting 'damper nozzle'

If you pm me your email I can send you some info.

if you do a search on racetech on this forum you will read about my less than positive experiances with Racetech emulators on a 90/6. If you go down this route you will heavily modify your damper rod. The basic racetech setup info regarding oil height is incorrect, so it is really down to you to come up with a setup that works.

The ate forks are more complicated than 'normal' damper road forks and the racetech instructions don't seem to reflect this, they might work fine on the later Brembo forks.....to a degree the spring loaded damper valve(nozzle) on the 90/6 forks, work just the same way as emulators do.

[Jean]

Sounds like your springs are shot.
Have you ALWAYS had this bike or did it belong to someone else who might have altered the front end?
Try Progressive's with a spacer on top.
The oil may be low too. or is lighter than you'd want.
(or a dozen other "things"....but you suspected that anyhow, didn't you?)

[Duane Ausherman]

Start by testing for stiction. My website has the ways to test forks.

Jean may be correct and your springs are sagged out. Your forks should have about double the travel of the rear shocks.

I wouldn't modify the forks until you get them working correctly. They probably don't need mods.

[jagarra]

I too am thinking my springs are sagging. Even when I am off the bike it sure is riding low. Too bad as it's great to be able to hit the ground flat footed for a change. Been checking springs, seems there are plenty of progressive units out there. a couple of straight rated springs, Sonic @ .65kg/mm and Race techs @ .90kg/mm.
Will take some measurements showing extended length vs compressed with me on it. Hope I wrote down how much oil I put in the forks.

[chasbmw]

The racetech springs are all made to a single length, you will need to fabricate a spacer and find out for yourself what length is required to give you the proper staic sag.

Rumor has it that the Progressive brand of front springs are too hard, I'm about to try a set of Wilbur's on my 90/6..

I'll send the info later on today.

[Major Softie]

The BMW Heavy Duty fork springs seem to be the most popular.

[jagarra]

MS,

I checked the dealer site and they listed 2 flavors, standard and reinforced. I figure the reinforced is the heavy duty, great price, $41.00 a side. For that price, I guess I will give them a whirl.


When I was doing searches looking for available springs, ran across an old thread on some BMW forum discussing the springs. Seems at one time the progressives from PSI were the "set up", then shifted the factory heavy duties. This went back about 9 years ago. Factory seems like a good place to start rather than after market offerings.
gg

[Duane Ausherman]

This is another example of the need to brag about a purchase, just because you spent the money and therefore find the product excellent. The progressive springs were never right for most people, they are too stiff.

The stock heavy duty springs work out well for most people. Super important is the fork alignment. It is very risky to change springs and expect to keep alignment. Even changing one at a time is risky.

I remember when the honeymoon was going on with San Jose speed parts. Then after a couple of years, people started bashing them. They had problems, but few took the time to install them correctly. They got flamed for the wrong reasons.

Same with Lester wheels. People got upset when they spun the bearings. That was BMW that set them up wrong in the first place. How could one expect to move the "bad stack" to a new wheel and not have the original problem. I didn't care for the Lesters, but they weren't to blame for the spun hubs.

[Seth]

I used the BMW heavy duty springs on an R90S and have been very happy with the results.
If you still find that you start off with too much sag, then pre-load them with a small spacer. If the sag is ok, but you still find them too soft, you can add some more oil to reducer the air in the forks, although I didn't find a need to do this.

I don't think you want any progressive (brand or otherwise) springs, as the initial softness is quickly compressed leaving you with little travel.