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Sportster Motorcycle Suspension, Frame, Forks, Handlebars, Fuel Tank, Oil Tank, Fenders Discuss Sportster Motorcycle Suspension, Frame, Forks, Handlebars, Fuel Tank, Oil Tank, Fenders problems, advice, and/or how tos.

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  #1  
Old 15th September 2007
XLFREAK XLFREAK is offline
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Default installed fork springs

ordered progressive lowered spring kit for my xl1200n but because the bike is already lowered so I just put in the top long spring without touching the small springs that go in the dampner rod.The kit comes with 3" pvc and is suppose to stick up above the tubes 1/2" but mine was 1/8" below the tube edge, so I took the 8" metal spacer from stock and halved it which gives me around 3/4" above tubes.Added 12oz. fluid per manual. My question is did I install it all wrong by not messing with the small dampner springs? In order to install these I think I have to totally remove the forks from the bike...HELP
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Old 15th September 2007
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That is about the same as I did to mine I might have a little more oil, I can't remember for sure. Mine works much better with that setup for my weight. I still get a very occurrence of bottoming the fork but it takes a mighty bump to do it. I weigh 196 lbs.

Have you tried riding it yet? what is your weight? what was the weight of the fork oil you put in?
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Old 15th September 2007
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My weight is 220 and used 15wt oil...manual says 12.3oz . The fork before would totally bottom out when braking but now it only travels about a 3rd of an inch which is great, that being said it seems somewhat stiff and could probably use 10wt oil and maybe drop the spacer back to 1/2" instead of the 3/4" I have now. I also installed the 412-4022B shocks, which are the stock 11" size with H/D springs in black of course...they seem to sag more than exspected and at the #2 notch sag around 1/2 to 3/4" which I don't like..ended up going to the 4th notch with a 1/4" or less sag which I like much better.To improve handleing I raised the forks 1/4" to lower the front end..it now measures 3/4" from the top of the 1 1/3" nut to the black rim of the fork tube, and it has improved the turn in when cornering,in fact I may be able to lower the front end some more, when looking from the side view it looks a little high still! I basicly need to ride it some more at these settings before I start tearing the front end apart again....working on the bike is fun but one can only take so much of a good thing. Have to make room for more fun on another wk/end.....
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Old 15th September 2007
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I also would like a detailed report. I am helping two other Nightster owners with suspension up grades.

I have not had the Nightster forks apart, but I have had my Roadster forks apart. I assume the Nightster forks are lowered from the factory by adding more rebound springs. I also assume the extra rebound springs in the "lowering kit" are used to lower the forks of bikes that are not already lowered from the factory. So, no, you do not need to use the short rebound springs because your forks are already lowered.

(EDIT: Since I wrote this I was able to compare a copy of an 06 to 07 parts breakdown of the forks. I cannot say for sure, but the Low and Nightster forks do not seem to be Roadster forks with extra rebound springs added to lower them. Something else is different, I don't know what. Read on.)

You can use preload, oil viscosity, and oil height to fine tune you forks. I was surprised how weak the stock Nightster fork springs were. They had to have a lot of preload just to support the weight of the bike. I tried to reduce the preload, but the stock springs were so weak, they could not even support the weight of the bike, so I had to put the stock amount of preload back in.

The first thing you want to do is determine how much travel the forks have. Slide up a rubber gaiter and put a plastic tie around the fork. You can either bounce on the handle bars, or hit the front brakes fairly hard to get the forks to bottom out. Measure how far the plastic tie moves up. Once you go through all the adjustments below, you will want to be sure you are using full travel.

EDIT: The best way to find out the full compression / maximum travel of the forks is to take the springs out and lift the lower fork tube all the way up into the upper fork tube. Measure the distance from any point on the lower fork, up to the the top of the upper fork with the forks fully extended and fully compressed, subract the two for your total travel. This is assuming the spring does not coil bind. Be carefull to not knock the bike over, and do not allow the weight of the wheel to pull on the brake lines at full extension. This point of full compression / maximum travel is important to find because you will use it as a point of reference for all future test rides and adjustments. You will want to make sure you are using all of the available travel when you hit the largest bump in the road that you usually ride over.

In general, you want to use enough preload so the forks sag about 1/4 of their full travel when you sit on the bike. But I don't know how true this is with Nightsters because they have so little travel to begin with. Since I am assuming the Progressive spring is heavier than the stock spring, you should be able to reduce preload. Usually the less preload, the better the forks will absorb smaller bumps in the road, and the better the ride will be. The minimum preload is where the bottom of the fork cap just touches the top of the preload spacer with the forks fully extended. The maximum preload is probably limiited to whatever you can use and still get the fork caps on. My guess would be the find the amount of preload that lets the fork just start to sag with rider weight on the bike.

The next thing is add 1 oz of fork oil to each leg. Adding oil stiffens up the last part of the fork travel and reduces bottoming out. I did this with Road Chick's bike, and it made a big difference for her. If you add 1 oz of oil, and the forks do not bottom out, I would go back and take out some preload to try and soften the ride. If the forks bottom out, add more preload. It may take a few test rides to determine the amoung of preload that works best for you. You do not want to add so much oil that the forks hydrolock at some point before maximum travel is reached.

EDIT: In general, your best set up will be where you have minimal preload provide the correct amount of rider sag (1/4 total travel) with enough oil to just prevent the forks from bottoming out. That way you are getting the softest ride, with the greatist resistance to bottoming out.

Oil viscosity. The lighter the better because the tire can track bumps better because the suspension can move down (compression) and up (rebound) faster. Heavier oil viscosity is a popular way to compensate for a weak spring, but should only be used as a last resort. I have ridden a Roadster with SE HD oil, and the forks were mush compared to mine.

EDIT: Road Chick tried the Harley heavy duty SE oil in her forks, and made them too stiff for her. Now that you have the preload and oil height set, try to reduce oil viscosity. If you can reduce the viscosity from what you had, the tire will track better. If the viscosity is too low, the tire will bounce undamped when you hit a series of small to medium bumps. If it does that, then you know you have gone too light and you will need to go back up to the next thicker viscosity. You should be able to tell a difference between each grade of 5, 10, 15, 20 w fork oils.

I know this is a lot of work. But the Nightster has so little suspension travel to begin with.
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Last edited by XLXR; 18th September 2007 at 04:43..
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Old 15th September 2007
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The Progressive springs displace more oil than the stock springs. The best way to check this is to remove the springs and fully collapse the forks. The oil should be 5 1/2" from the top of the fork tube. You are right not to mess with the smaller springs. Be sure to use a metal washer between the spring and preload tube. Check with Progressive suspension to get the correct preload numbers for your weight and model of Sportster.
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Old 15th September 2007
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Hoghead - great report, thanks. Your report of the Progressive spring in a Nightster is the first one I have read.

Using 1/3 inch of travel is too little. I would think that is because the Progessive spring is much stiffer than the stock. I would think changing to 10 w oil and reducing preload until you are using full fork travel is a good idea. It could be the Progressive spring is so stiff, you won't need to add the extra 1 oz of fork oil.

I know what you mean about wanting to ride more instead of working on it.

On second thought, 12.3 oz's seems to be alot. Are you sure that is what the manual said? Are you sure you pumped the forks up and down to drain out all the original oil? Too much oil could be the cause of not using all the travel.

Last edited by XLXR; 15th September 2007 at 21:50..
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Old 16th September 2007
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Originally Posted by XLXR View Post
I also would like a detailed report. I am helping two other Nightster owners with suspension up grades.

I have not had the Nightster forks apart, but I have had my Roadster forks apart. I assume the Nightster forks are lowered from the factory by adding more rebound springs. I also assume the extra rebound springs in the "lowering kit" are used to lower the forks of bikes that are not already lowered from the factory. So, no, you do not need to use the short rebound springs because your forks are already lowered.
Is the fork set up the same on the XLs except H-D just changed the springs/damper tube in the forks to lower the N? I want to add more travel to the front of my N, any ideas on what I would need to do this? I am thinking of raising it up to the R height, but keeping it at about the same rake. I would like at least 1" more travel
cb
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Old 16th September 2007
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The fork springs in the 07 Nightster were a lot softer than the stock ones that came out of my 06 Roadster. I put them next to each other on the bench and the wire size was noticably smaller. The Nightster also had so much more preload, I had to have 2 girls help me get the fork caps back on.

You can check HD part numbers to see if the damper tubes are the same. But that won't work for the fork tubes, because the Nightster tubes are black.

I do not know how the Nightster forks are actually lowered because I have not taken them that far apart. However, on my Roadster forks there is a small rebound spring between the fork tubes to keep them from banging together at full extension. The typical lowering kit consists of extra rebound springs you add to lower the forks. If HD used extra lowering springs to lower the forks, then all you would have to do is take apart the forks and remove the extra lowering springs. The ones I have seen are about one inch long, taking out one spring will raise the forks one inch. It is possible there is only one 3 inch long spring. If that is the case, you will have to get the shorter rebound springs to replace it with. No one knows if HD made any other changes to prevent you from raising the forks.

The next question will be what fork spring to replace the stock on with. If you weigh 140 lbs, the stock spring might be OK if you adjust the preload and oil height accordingly. If you weigh 180 lbs, the standard Progressive spring should work. If you weigh 230 or more, try the Works Dual Rate springs.

Next question, what shocks are you planning on using? Whittlebeast just took apart Road Chicks stock shocks, only had one inch of travel. Although they had a progressive spring 85/120 lbs (if I remember correctly) the travel was so short, the spring never gets to the high rate. Unless of course, you are so heavy you never get to use the low rate.
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Old 16th September 2007
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Quote:
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The Progressive springs displace more oil than the stock springs. The best way to check this is to remove the springs and fully collapse the forks. The oil should be 5 1/2" from the top of the fork tube. You are right not to mess with the smaller springs. Be sure to use a metal washer between the spring and preload tube. Check with Progressive suspension to get the correct preload numbers for your weight and model of Sportster.
The 5 1/2 inch oil height only applies if you have the forks off the bike and held vertical. When the forks are on the bike, they are tilted so the distance from the oil level to the top of the forks is different front to rear. Fill a glass half full of water and tilt it, you will see what I mean.
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Next question, what shocks are you planning on using? Whittlebeast just took apart Road Chicks stock shocks, only had one inch of travel. Although they had a progressive spring 85/120 lbs (if I remember correctly) the travel was so short, the spring never gets to the high rate. Unless of course, you are so heavy you never get to use the low rate.
I have progressive 412 12" rear shocks that just came in the mail, so the first thing I am going to to do is install these and see what difference they make in over all ride quality.

I am right at the 180# weight so I am probably going to go with the progressive front springs. However, I am not sure how to tune the front if I am able to increase the fork travel, unless I go with the R stock set up and use the aftermarket springs for the R? I will then probably go with progressive 418s 12.5" or 13", what ever will give me a similar rake as I have now.

What is the front fork travel difference between the R and N ?

I am going to go to the dealer and get a parts list for the R and the N front forks.

Are there any on-line repair manuals for the 07' XL , I have to order one from the dealer so I don't have a manual yet.

Thanks, CB
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