Building a Hyosung GT650RS

Why?

A few years ago, we bought a Hyosung GT650R for my wife. We chose the fully-faired GT650R model over the naked GT650 or the half-faired GT650S because it looked so purty. Unfortunately, age has cosught up with both our bodies and the leaned-over riding position is not good for any more than a short ride.
Late in 2011 I bought a Hyosung Gt650S for myself. A short ride on it convinced us both that it was the model we should have bought in the first place.

Since we already had the GT650R, and we were very happy with its performance, and it would cost quite a bit to trade in the GT650R for a GT650S, we decided to go ahead and buy the necessary parts to and GT650S handlebars and screen, and convert it to a GT650RS.

Even though Hyosung doesn't make a GT250S, if you wanted to you would be able to use this same procedure to make one out of a GT250R.

How?

It's necessary to go shopping for some parts before you start. The list below is as complete as I can make it. I found the parts diagrams here: http://www.alpha-sports.com/hyosung_parts.htm

Hyosung Part Number Description Catalogue Price Comments
56501HN9100 Mirror set $89 An aftermarket set is much cheaper
56110HN9102 Handlebar tube $81 Used or aftermarket parts are cheaper
56211-35C00 Lower handlebar holder brackets ( x 2) $20 Can use dirt-bike parts if you prefer.
56171HF4601 Upper handlebar bracket $24 Can use dirt-bike parts if you prefer.
09106H08458 Handlebar bracket bolts ( x 4) $14 These are just M8x1.25 bolts, which can be found at the hardware store.
n/a Handlebar end weights $20-$30 You'll want these to damp down the vibrations.
58200HN9104 Clutch cable $21 You need the factory part.
58300HN9104 Throttle cable $31 You need the factory part.
58600HN9103 Throttle return cable $37 You need the factory part.
58410HN9103 Choke cable $47 You need the factory part.
59450HN9100 Upper brake hose $36 Aftermarket parts, or parts for other bikes will fit.
59460HN9100 Lower right brake hose $35 Aftermarket parts, or parts for other bikes will fit.
59470HN9100 Lower left brake hose $35 Aftermarket parts, or parts for other bikes will fit.
51511HN9100 Front brake hose T-piece $? Aftermarket parts, or parts for other bikes will fit.
94611HP9203HPA Windscreen (GT650S) $122 An aftermarket double-bubble tinted screen looks better, and is cheaper (~$80).

Handlebars

Assembling the handlebars was straightforward. The GT650R upper triple tree has thickened points in the casting ready to be drilled and tapped to mount the handlebars. Note that if you're planning to buy a new upper triple tree rather than modifying your own the GT650 (naked) bike uses a different casting to the GT650R and GT650S.

It's perfectly possible to use a different handlebar tube, provided it is the same diameter as the Hyosung one and doesn't bump the clutch lever or brake master cylinder windscreen at full steering lock. You could also use dirt bike-style brackets for the steering head, provided that their mounting holes line up with the casting on the upper triple tree.

Of course if you want to go crazy and mount ape hangers, you'll need to get custom-made clutch/throttle/choke cables, and extend the electrical cables as well.


A view of the factory GT650S.
Close-up of the GT650S handlebar assembly.
Upper triple tree and handlebars removed from the GT650R.

The underside of the GT650R upper triple tree, showing the mounting points in the casting.
Drilling out the holes to 6.8mm (17/64") prior to tapping. It's best to use a drill press, and to drill a 2mm pilot hole first.
Threading the holes using an M8x1.25 tap. Take your time and use plenty of oil on the tap.

New handlebars bolted into position on the top triple tree.
The difference in position between the old clip-on handlebars and the new ones.

Cables

The GT650R throttle, clutch and choke cables are too short to fit the higher handlebars. You will need to remove the airbox and carburettors to replace them with the new, longer ones. DO NOT try to remove the choke cables from the carburettors without first removing them from the bike, or you WILL ruin the screw heads (guess how I know) :-).

Fortunately the electrical cables have enough extra length tucked away in the frame to reach without any problems.

It's best to replace 1 cable at a time, so that you can route them through the frame the same way (that's another thing that I didn't do, and it's funny how quickly you can forget!)


Clutch lever and cable fitted.
Brake master cylinder in position.
Switch blocks mounted. These each need a 5.5mm hole drilled through the handlebar for their locator pins - it's best to wait until you have the screen fitted and the handlebars adjusted to avoid collisions before drilling these.

Re-assembly complete.
Re-assembly complete.
Just need to re-fit the lower fairing

Brakes

You will need a longer upper brake hose, so that it will reach the master cylinder in the new higher location. Our GT650R had a brake T-piece that looks like a matchbox, with the brake hoses "crimped" into a permanent connection. Most motorcycles use a bolted-together T-piece, with "banjos" on the ends of the brake hoses. I converted our GT650RS to this style of brake hose so that we can fit it with braided stainless-steel brake lines in the future (this will improve the "feel" and power of the brake system over the standard rubber hoses).

I had some trouble bleeding the brake system the old-fashioned way (squeeze and hold the lever, loosen the bleed nipple on the caliper, retighten the bleed nipple, repeat the process), so I constructed a primitive "pressure bleeder" system from a piece of 2mm thick aluminium strip and a cut-up bicycle tube.

To use the system, follow these steps:

  • Remove the master cylinder lid;
  • Fill the master cylinder as full as possible with brake fluid;
  • Fit the pressure bleeder lid and tighten the mounting screws;
  • Attach a hand pump and pump up to around 30psi;
  • Bleed from the caliper bleed nipple as usual.

    Be very careful not to run the master cylinder reservoir dry, as this method will send a lot of fluid through the system very quickly. This speed is actually a good thing, as it seems to prevent bubbles from getting stuck in the nooks and crannies of the brake system. Bleeding brakes the old-fashioned way often involved unbolting the calipers and holding them at different angles while tapping them with a spanner to dislodge the bubbles, but I had no problems this time.


    Original GT650R front brake hoses.
    Close-up of "matchbox"-style T-piece.
    Bolt-together T-piece now fitted (viewed from below).

    Pressure bleeder fitted.
    Pressure bleeder pumped up to 30psi.

    The final product

    It's much more comfortable to ride now, and still looks great. (And I've just bought a GT650R lower fairing kit to transform my bike into a GT650SR). :-)

    Left view.
    Front view.
    Right view.


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