I'm doing up an 08 Nightster to ride over the summer. It's a stock bike with very little use and only 3000 miles on it.

I have serviced the bike and changed all the fluids, including the fork oil.
I have 12.3 ounces of type E with a level of 122mm in each fork leg.
That's about what came out and what I believe should go in.
Although I have seen figures quoting more oil and higher level.

I find the front forks very soft with a lot of sag and almost no travel before they bottom out.

I weigh about 160 pounds. A have a set of Racetech .9kg springs (almost their heaviest recommended for this bike). Any views on how these would perform and should I just install them with the stock spacers.

I'm not too sure about how much sag I should have, with so little total travel in total, I suspect not much. I understand that the forks are too short to ever give a really plush ride, but I just want it to be as good as I can easily and inexpensively get. I'm in the UK and there is very little aftermarket expertise readily available.

Any advice from past experiences welcomed.

 

You have .90kg springs.
http://racetech.com/ProductSearch/2/...htster/2007-12
They should be a bit stiff , but OK , I used 160lbs to get this info.
Looks like 25mm is recommended spring preload.
When setting the fork oil level , you must remove the springs , collapse the forks , and measure from the top of the oil level to the top of the tube.
Don't believe what came out is correct.
The oil level is important in that you are actually setting the amount of air the fork will have when you're done.
A higher oil level will make them stiffer , lower is softer.
Racetech recommends 160mm for the oil level.
They have a worksheet for the spring preload on a link from the page.
Generally , the way Progressive suspension recommends , the preload would be 1/3 travel with rider sag.
So if you had a 6" stroke on the forks and shocks , they should sag 2" with you sitting on the bike with a full tank of fuel.
This is how I set my bike up and it works really well.
I used Roadster damper tubes ( 2" longer than stock ) which gave me a total travel of 5 1/4" instead of the stock 3 1/2"
This way with the sag set at 1 3/4" , I still have 3 1/2" of down travel.
With Progressive springs , 7wt , set at 6.340" the forks are supple , don't bottom , react quickly to bumps , nice ride.
I'm pretty close to the same weight as you ~10 lbs.
Mick

 

Thank you, some good information for me in there. I will probably need to cut the spacers to achieve the 25mm preload. I going to give them a try, I'm a bit concerned at their oil level recommendation, that's a lot less than the stock quantity. I know less oil softens and more stiffens.

 

160mm is just about 6.30" which is pretty close to my spec on the '48.
Remember you have heavier springs , so the air space could be lower and be fine.
I had a few minutes when I did mine and just for grins , added air valves while I was at it.
They're just a 1/8" pipe thread schrader valve , Napa # 90290 , I have a touring bike pump for the pressure.



This way I could add a couple pounds if I goofed up on the preload or If I needed more for 2 up riding.
I can remove the valves and suck out/measure the fluid and do a quick change in weight to fine tune also.
I also ran the tubes even at the top of the trees instead of up slightly like the spec.
Mick

 

Those caps look really good and very useful, how much air pressure are you running. I assume you have had no leaking fork seal issues with this.

 

I have Race Tech single-rate springs in my SuperLow. With the sag set correctly the bike sits around an inch higher when sitting on it, but at least I get decent travel and a bit more comfort. I also fitted longer shocks, so it is now a Super-not-so-Low!

 

With the bike on a lift (extented suspension) I run 0 lbs of air.
I would probably read some pressure at ride height , but never checked.
It's just a conversion starter and later on easy maintenance mod.
I did the forks with 3,000 miles on the bike , so all the bushings and seals were OK at the time.
The gunk that I flushed out of the fork sliders was quite impressive though , I was glad I did it then , not later in mileage.
grbrown , do you remember the spring rate you used on your (previously) super low ?
Mick

 

Hi Gr, I see you are in the UK as well. As we are international HD spec in the UK we already have the longer rear shocks, approx 13.5" long. I'm happy enough with the back end, it's just the front is poor. I had another Nightster a couple of years ago, but I don't remember it being that bad, maybe I'm just getting old............

I'm running the rear shocks with the preload set in the second (middle) of the three preload positions.

 

Mick, no I don't and unfortunately the dealer I bought them from didn't include that info on his invoice. I'm around 190 pounds, so I suspect they are the same as yours.