A lack in continuity

I did this a while ago but forgot to blog it (God knows how, bloggin is my noggin)..

Bought some 2" under fork tubes from Frank

And a repro later-style damper from V-twin manufatcats.  Better than the long cartridge(?) style original K-model ones, apparently.  Also better for lowering your forks as you don't need to cut down the damper.

I can't identify the different sportster fork sliders but these ones have a waisted bottom (photo above), no seal at the top (photo below) and the K fender wings (obviously).  Anyone know?

The bushings were a bit tight for the new tubes so I opened them up a bit with this clever little contraption.

Those later dampers need a larger hole in the bottom than the K's, fortunately these were already big - maybe altered years ago or later-than-I-thought sportster forks?

So this is the stock length spring in the assembled lower forks.  Last stage is just to cut 2" off.

 THIS DIDN'T WORK

THIS DIDN"T WORK WELL

(in the end I used a thin cut off wheel on an angle grinder - much neater)

BEFORE

AFTER

 

I lowered my K model forks by two inches.  There are several ways to lower forks but this way is easily the best.

Spring mechanics:

Changing the preload spacer does not change the stiffness.
Changing the preload only affects the ride height.
Reducing the preload will lower your bike but it will likely bottom out a lot.

Putting a spacer on the bottom of the damper will reduce the travel.
It will stop your forks extending fully and the bike will sit lower.
Reduced travel has it's downsides and you will need different springs or small bumps will not be absorbed.

Shorter forks and shorter springs will retain full travel and just sit lower.
Unless your springs are really short and constrict travel.

Shorter springs are stiffer.  This means they move less for the same load.
Spring length, geometry (ie coil density) and material are the only factors which affect stiffness.

Dampers and oil affect damping - how quickly forks react.

When lowering my forks I pretty much forgot all the maths and freestyled it.  I wanted low stiffness to maximise the travel off-road so I left my springs as long as possible with normal preload (a third of the total travel when sitting on the bike) which basically meant no preload spacer.

It worked well, the forks bottom out with the sliders a mere 1mm from the lower tree and they've only bottomed out once when riding when I did a fairly large jump.  The stance looks a bit tighter as well which was the main point I guess.

Special K

Preparation for Red Marley started with my forks.  As much as I love the Mullins trees, the rigid forks were hardly suitable for a hill climb.  To be honest they are hardly suitable for anything but I had to do them after spending so much time thinking about it.  Realising your ideas is important, even if you just realise they're shit.

I got a nice set of K-model forks.  It took me a whole day to rebuild them and install the triple trees.  The stem and fork tubes had too much chrome so the tubes would fit in the trees and the stem nut wouldn't fit on the stem.  I was sweating everywhere by the end of it, when you're too unfit to force a front end together then maybe it's time to go for a jog.

Took another day to make a new axle

 

 

Finally I had some bizarre luck - the front hub fit so perfectly between the forks that, with the brake plate right up against the left fork, the wheel alignment was off by only 0.030", so I didn't bother making a spacer.  And one of the spacers I made for my rigid forks was only 0.012" too long for the other side which took only 0.35 seconds to adapt.

The forks are too long, have too much play in the bushings and the preload is too high but they still make for a 1000% improvement over what I had before.

Next weekend - practice.

Last minute bits

 

Exhaust clamps

 Brake stay

Dead man's switch

Blotto parts

Check the rear shocks - pure Loony Tunes!

Limbo

Took 0.878" out of my forks in the quest for perfect stance.

 

How to fuck up a front end:

1.  Buy some Mullins 35mm trees and ebay some forks.  Add to frame and congratulate yourself on having great taste when it comes to narrow front-ends.

2.  Apply ruler between forks.  Accompany ruler round swapmeets, scrouge ebay, wrangle advice until realisation that the only drum your ruler vaguely approves of is from a cub 50 scooter which has an axle diameter of about 6.734 mm.

3.  Decide:  brakes or suspension.  Or machine your own hub but by that time you've already laced a Kempton found drum to the Borrani rim even though you knew it wouldn't fit but it was a twin leading shoe and you got carried away.  Brakes over suspension it is.

Chop (all important word) the fork tubes.

This is actually the first part I ever made on a lathe.

Milling in the lathe.

Taper practicing.

Taper turning.

At this point I drilled and reamed a hole.  Actually I snapped the pilot drill half way but seeing as it took me like two days making this part and working out how to use the lathe, I alternated.  Plunged an end-mill in about 2mm (the snapped drill bit rising into the hole in the end-mill), oxy-acetylened it, hammered protruding drill bit flat, plunged the end-mill another 2mm, repeat 10 times until mad with the world then enlarge messy hole to correct size.

Make a little axle.

Trim the fork tube caps.

 

OPTIONAL:  Advise all comfort cynics that you spent everyday for the last four years riding a completely rigid bicycle with 19mm cross-section tubular tyres at 180psi around crappy, pot-holed, English roads and you only had to see the doctor about an embarrassing lump on your anus once.  This should distract them from knowing best about vibration damage, cornering-grip, and other borings.