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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 10th April 2008
cbnightster's Avatar
cbnightster cbnightster is offline
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Default Inexpensive front suspension upgrade for 1200N & 883L

I have brought up the issue of replacing the damper tube in the 1200N with the damper tube in the 1200L in the past. There was skepticism to this swap and rightly so because I had nothing to back up my statements, except logic. So, I bought 2 1200L damper tubes (21.00 ea.) and replaced the stock N tubes with them. This swap gives you a minimum of 1/2" more travel which both the N and 883 desperately need, it seems the travel increase is actually 3/4" and I don't know why since the tube is only 1/2" longer. This was the only change I made as I used the stock preload spacer, spring and factory 12.3 oz of H-D type e oil. I did not want to take my bike apart to test them since I have a different set of forks already installed, that said, I went ahead and installed them on my bike the other day to test them out. I weigh 180 so keep this in mind. I am very impressed with the action of the fork now, compression damping or damping in general is much better, I suspect due to the different damper tube design. I am using all the travel and right at bottoming out with the stock set up. If you are 10-20lbs lighter than me then it would probably work even better.
If I were going to use these I would first try 1oz more oil , this would probably keep them from bottoming out as they are, or maybe a heavier oil. The next step I would probably add just enough preload to get the rider sag right at 1" as it is it is about 1 3/8". I have read some posts where others are adding more preload to the stockfork in order to get more travel. I tried this with the stock forks and was very disappointed in the ride quality, tops out, which is no good. This set up would really benefit with the addition of a progressive fork spring or works spring! This is of course objective and your results will vary and you will need to tune this as you would any other spring change to suit your riding habits, etc.

Top tube is stock N/883L



I posted about this in another thread , http://xlforum.net/forums/s...=180874&page=7 not sure how many with Ns or 883s read it, but I had not tested it out either.
This is an inexpensive mod and I think that most with the N & 883 low suspensions would benefit and the increase in ride height is minimal and you can always raise the tubes up in the triple.
I would also emphasize that it is a really basic operation to remove the fork tubes and disassemble them install the tubes and reassemble them with basic tools and homemade seal installer. Get a manual!
Just thought I would throw this out as a suggestion to help with the (IMHO) poor stock suspension.

CB
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  #2  
Old 11th April 2008
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Thumbs up You beat me and thanks for the picture.

I finally finished the same damper tube change 2 days ago, I also changed to progressive (1157) springs (1" preload - even with top of tube) and added the air mod. I also went with fork tubes that measure 2.25" longer than stock. All I can say is WOW, the difference is night and day.

I am using 13oz of Amsoil #10 fork oil, I started with 0 psi that gave me 2" of rider sag and had some bottoming - not jarring but bottoming. So I have worked my way up to 5 psi, the rider sag is at about 1.25" and everything feels great. Both the high and low speed damping with the 1200L parts are far superior to the L/N damper tubes.

My ever expanding midsection has me at 195 right now. The fork mods combined with the RK 13" air shocks (with 1" lowering blocks) at 0 psi give me a great solo ride and the rough road handling is way better.

To answer a few other questions that always seem to be asked
- the seat height is up 1.25" from stock (with the air shocks, with out was about 0.5")
- the trail measures right at 5.0"
- total travel added with the 1200L dampers is 0.75"
- with me on the bike the frame rails are .25" higher in the front than at the swing arm (less difference than a stock C)
- the plating (sp?) on the stock fork tubes is the same from top to bottom so I would see no problem with using the even longer C/R damper tube for a cheap and easy travel increase... except this will increase the ride height more than the 1200L dampers.


Thanks to XLXR, Whittle, cb and everyone else that has delt with the suspension blues - y'all rock!



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  #3  
Old 12th April 2008
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Default

I assume you're using the longer fork tubes like on the 1200R. I am not sure why you did that because you don't gain travel, just fender clearance. You might as well go with the longer damper tube like in the 1200/883R. You made so many changes it is hard to tell what is really working for you, but if it is working well then don't fix what isn't broken.

My reasoning behind this mod was to gain a little travel for the N and not drastically change the ride height at minimal cost, an unintended consequence was what I feel is much better damping characteristics with the 1200L damper tube. I wish I would have paid attention to how the 1200R tube is drilled and the size of the holes.
CB
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Old 12th April 2008
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Quote:
Originally Posted by Moe47 View Post
I finally finished the same damper tube change 2 days ago, I also changed to progressive (1157) springs (1" preload - even with top of tube) and added the air mod. I also went with fork tubes that measure 2.25" longer than stock. All I can say is WOW, the difference is night and day.

I am using 13oz of Amsoil #10 fork oil, I started with 0 psi that gave me 2" of rider sag and had some bottoming - not jarring but bottoming. So I have worked my way up to 5 psi, the rider sag is at about 1.25" and everything feels great. Both the high and low speed damping with the 1200L parts are far superior to the L/N damper tubes.
I find some things confusing?

So you went with longer fork tubes, this should have raised your ride height?

You basically have added no preload to your springs and your rider sag with longer fork tubes and the 1200L damper tubes is 2" and you adjusted the rider sag to 1.25" with air pressure, correct?

CB
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  #5  
Old 12th April 2008
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cbnightster,

Did you have to replace the seals? or was it just oil and damper tubes?

I have the progressive springs and the air mod on mine with 15w oil. I really think I need just a little more travel. I actually think on the largest bumps when It bottoms I think it is the springs reaching their full compression rather than the forks bottoming. I am pretty sure that extra 1/2"-3/4" might just be what I need. I will probably switch to the lighter weight oil.
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  #6  
Old 12th April 2008
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Exclamation Ride height.

Quote:
Originally Posted by cbnightster View Post
I find some things confusing?

So you went with longer fork tubes, this should have raised your ride height?

You basically have added no preload to your springs and your rider sag with longer fork tubes and the 1200L damper tubes is 2" and you adjusted the rider sag to 1.25" with air pressure, correct?

CB
Yes the longer tubes did raise the ride height, I wanted to lengthen the wheel base a little so that is where I went, and I also needed to add to the forks a little to try and keep the frame level because of the extra height I gained from the RK air shocks.

You are partially correct on the preload. 0 preload would be with the spacer or spring at the level the cap screwed in, with the spacer at the top of the tube you get about 0.75-1" of preload, which would not be enough without the air mod. I kept the preload to a minimum on Whittlebeasts recommendation and it seems to work really well.

All in all I totally agree with you're assessment on the 1200L damper tube being much better than the N/L damper and a cheap upgrade path. I did not use the C/R tube because that would have put my ride height too high to keep the frame close to level, because of the tubes I got so cheap I had to change my path a little.


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  #7  
Old 12th April 2008
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Quote:
Originally Posted by kenfm2000 View Post
cbnightster,

Did you have to replace the seals? or was it just oil and damper tubes?
I only changed the damper tubes and the oil HD type E (10wt?). I did not replace the seals since they have very low miles on them. I understand there are aftermarket low stiction seals out there, it might be a good idea to use those if you have a lot of miles on your seals. To me, the H-D seals seem to drag a little more than I would like. Anyone else feel this way?

Quote:
Originally Posted by kenfm2000 View Post
I have the progressive springs and the air mod on mine with 15w oil. I really think I need just a little more travel. I actually think on the largest bumps when It bottoms I think it is the springs reaching their full compression rather than the forks bottoming. I am pretty sure that extra 1/2"-3/4" might just be what I need. I will probably switch to the lighter weight oil.
I agree that the spring may be coil binding and any travel increase on the N or 883L is an improvement, period. I would change the tube and set it up with the stock amount of oil, 1" of rider sag to base line it and go from there. Tedious yes, but you do not want to throw to many variables at it all at one time.

CB
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