78E/81SH fork lowering fun

[Catmaigne]

My main bike is a 81SH but it's a little too tall for me. I'm 5'10" but have pretty short legs so keeping my footing at intersections is a bit of a hassle because I'm on my toes. I'd like to drop the front fork about 1.5" inches in addition to a .75" lowering in the rear with a set of standard length Sportster shocks to help out a bit. I'm going to do a bit of grinding to the stop for the kickstand to accommodate the new height so the bike doesn't fall over while on the side stand. The bike has a Mac 4-2 so clearance isn't that much of an issue.

The bike is more a cruiser and I'm not too concerned with it's cornering abilities so I think shelling out for some Progressives in this case would be unnecessary. I REALLY don't want to cut my Special springs that have seen 33K+. I think they'll sag like hell.

I have a 78E parts bike with about half the mileage and was going to swap the fork springs and caps over. I'm aware that the E fork springs are about 4" shorter than the SH ones and would require a PVC spacer to get the exact height I'm looking for. The E caps are non air and about 1" longer than my SH's so I think the spacer would need to be about 1-1.5" to get the desired height. I would also be able to get my handlebars to a more desirable position because the SH air caps are in the way (and are pretty ugly too).

The question:

Am I going to have to tinker with the fork damper when converting from air to non air forks with a spacer? Where could I get a hardened spacer for my Special damper? I've heard that making one is a bad idea.

[crazy steve]

Well, you have several things going on here....

First, you can't swap the E and SH fork caps; the threads are different. And you don't want to use shorter main springs to lower the bike; that will give you way too soft of a spring rate and the bike will bottom out at the drop of a hat. You have to maintain a certain amount of preload for the springs to work right.

But there is a way to 'shorten' the forks fairly easily. Disassemble the forks; you need to pull the damper out to get to the rebound spring. By lengthening the rebound spring, you'll lower the bike by the same amount. You can do this by either finding a longer spring, or doubling up on the stock springs.

Now, there is a couple of downsides to this. First, you'll lose fork travel; however much you lower the bike will be the loss. You may find that the preload with the stock springs may be too much if you lower too far. If you substitute the shorter 'standard' springs, the spacer will need to protrude from the fork tube at least about 1/2" for correct preload, although a bit more would be good. The spacer can be PVC, but install a metal washer between the plastic and the spring.

My recommendation would be to double the rebound springs, and try the stock special springs to start. This will give about 1" lower. You can gain about another 1/2" by moving the tubes up in the fork trees. If this proves to be much too firm (remember, you can still adjust air pressure), only then would I try the 'standard' springs. And I'd start with 'long' spacers (1" out of the forks) and trim them no more than 1/4" at a time until you're happy.

You can also experiment with adding more fork oil. Adding 10cc will 'firm' the forks up. You should be able to add up to 30cc for 'tuning' before they get too stiff.

This help?

[Catmaigne]

The reason I wanted to swap the fork caps was because my bike has clubmans. The SH caps make it a tight fit and don't allow me to get the angle I'd prefer. Because of this I can't move the forks up higher in the trees either. Is there a smaller fork cap from another bike I can use? (One with a hex and non air would be preferred)

I guess it would be a good idea to order some Progressives then being that I can only lower the bike by shimming the damper spring. Would the Progressives fare well with a 1.5" loss of travel? I was hoping it would be a nicer overall ride that wouldn't bottom out like stock spring with added preload. Also, what should I make the 1.5" damper spacer out of or where could I buy one? I remember reading that PVC won't stand up to it.

[crazy steve]

I'm not aware of any other fork caps that would work; all the Special forks had the air-assist. You might be able to find a set off another bike if you dig around in a wrecking yard...

You have one other option, but it's a bit more expensive. Have a set of custom-length fork tubes built and use the progressive springs. This has the advantage of not losing any fork travel, and you can simply shorten the supplied spring spacers by the amount the tubes are shorter. You may even be able to have the cap threads changed to the 'standard' threads and be able to use those caps. Look here: http://www.xs11.com/forum/showthread...108#post397108

[DGXSER]

I have read / heard that you can add a spacer to the bottom of the fork, the rebound spring. Same effect as Steve mentioned getting a longer spring as far as height adjustment. Would have to stiffen up the fork as well. Maybe a cheaper way of getting the same result.

[crazy steve]

The spacer/longer spring is how those 'lowering' kits for V-twins typically work. But the kits also come with special main springs, something that's lacking in this case. And loss of fork travel is also an affect from this method, so I'm not a fan of them.

The problem with a spacer is if it's too long, it may cover some holes in the damper and upset handling. A spring is 'open' and won't cause that problem.

[DGXSER]

The spacer for lowering would go above the rebound spring, under the cylinder seal, if I understand the setup correctly, and therefore it should not cover any holes. It is a bit harsher /stiffer ride than adding longer springs or putting an additional stock rebound spring in, as the spacer has no give.

[Catmaigne]

Well, I could steal the rebound springs from the Standard forks but I'll still need more to get the desired drop. Anyone know the ID/OD of a spring I would need and how stiff it should be?

[crazy steve]

The spring should be .75" inside and 1" outside. These need to be pretty stiff; they're there mostly to prevent a metal-on-metal 'shock' when the fork extends. I've seen old valve springs used. Make sure both sides are equal length.

And there is a hole in the damper that would be covered by a 1.5" spacer; I just went and looked....

Keep in mind you're reducing fork travel by over 20%, so some degrading of handling should be expected. And getting the main spring preload right will be critical. Check to see how much 'sag' you have now (how far the forks compress with you on the bike) and you'll want no more than that after, preferably a bit less.

[fredintoon]

My main bike is a 81SH but it's a little too tall for me. - - -
Am I going to have to tinker with the fork damper when converting from air to non air forks with a spacer? Where could I get a hardened spacer for my Special damper? I've heard that making one is a bad idea.

Hi Michael,
FYI, Progressive sells the same spring kit for Standards and for Specials
It has the shorter Standard springs and a plastic sleeve that you saw up to make spacers to fit the springs into Special fork legs.
What you can do is swap in the complete Standard forks (complete with 'trees, fender etc) which is good as the Standard forks have better brake calipers.
Whichever forks you decide on, ditch the clubman bars, slide the fork tubes up through the 'trees and put clip-on bars either onto the stubs atop the upper 'tree or below it, whichever you find the most comfortable.

[Catmaigne]

The Standard forks have some pitting on the chrome so I won't be using them. I also sold the trees so I would need to buy another set which seems like a hassle.

I was looking at clip ons but I thought the triple tree would look awkward with the handlebar mounts empty and the clubmans were pretty cheap. If they're too uncomfortable I may consider switching to clip ons with a XJ1100 upper triple tree, but I love the way they look currently so I may keep them.



I forgot I have 20mm handlebar spacers from my drags so I'm going to try to find a better angle with the clubmans.