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Looking for an inexpensive upside down (USD) front end swap or conversion for your Honda CX500, GL500, CX650 or GL650? Here's some information on the Hyosung GT250 Comet, GT250R, GT650, GT650R front ends which are usually available cheaply in Oz - twice in 2017 I acquired two entire GT250Rs that were roadworthy for $250 or less.
Below is piecemeal but a number of important points and things to consider about the conversion. We're talking about primarily the GT250 and GT250R here. Incidentally, Hyosung have been making motorcycles since 1978 and have sold millions to date.
First up - the GT250 front end has normal handlebars and a brake caliper on the left hand side only.
The GT250R has clip-on handlebars and brake calipers on both sides.
All of the Hyosung front ends that we have seen so far (2008 or 2009 is the latest we have used) have been upside down forks utilising conventional damper rod technology - the same as what is in all of the stock CX500 front ends. No modern cartridge-style forks here.
The Hyosung front end is 17" instead of the CX500's default 19", or 18" for the Turbos and Sports/Euro models.
The front end from axle center to top of fork tube is approximately the same length as the CDI CX500 front end. Note that since the front wheel is 2" smaller in diameter the front end will be 1" closer to the ground due to the smaller wheel size. This has handling implications - not only will the bike feel like it wants to turn in more quickly thanks to the smaller wheel size, it will also have an altered rake and trail thanks to the difference.
The brake calipers are TCIC branded (Tae Chul Industrial Co.) sliding pin calipers and are twin piston per caliper.
Aesthetically the upper triple clamp is totally flat:
The GT250 Comet's front end may only come with one caliper and rotor but you can acquire the right-handed caliper and rotor to get a dual-brake setup. The GT250 has the necessary brackets on the fork lower and holes in the front wheel to attach a caliper and brake rotor respectively in the examples that we have seen. Note that if you do this your front master cylinder may be under-specced for a dual-setup - worth checking.
With dual brakes on both setups the Hyosung front end is 1.9kg lighter than the stock CX500 33mm front end with reverse Comstar fitted. 26.1kg vs. 28.0kg.
The steering stem is shorter - approx. 205mm vs. the CX500's 223mm - so you have less threads to attach the top nut to. Apparently you get about five threads above the top triple tree.
The other main concern is bearing availability - the lower bearing that would be necessary to use this stem in a CX/GL frame isn't produced so you need to find a solution to alter the size of one or the other (stem or frame). Common solutions here are to get a machine shop to make up a sleeve for the stem, either with a lip at the bottom so it doesn't ride up the inside of the bearing or welded to the stem like so:
Lower bearing on the sleeve:
Upper bearing used in this case:
The lower bearing can be 30x52mm if the stem is spaced out and the upper is 25x48.5mm.
As an alternative the steering stem may be able to be pressed out of the CX triple tree (after grinding off the weld) and perhaps pressed in to the Hyosung triple tree - anyone tried this?
We will update with more information as it comes to us. Got some information on this front end swap? Hit me up at the contact page. Thanks to Mitch for most of the info above!
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