1980 GS450 "Sport" - Resto / Mod

[Big Rich]

I think I wasn't clear: the California model carbs have the vents, the ones I'm rebuilding do not.

[pete]

Ok, now I get it

[Big Rich]

Messing with the jetting a little bit today: originally I had 127.5 mains in and there was a little lack of power on the top end. So I stopped at the dealer while I was running errands and bought a couple 130's (he wasn't sure of the price so he only charged me for one of them!). Come to find out that lack of power on top was from a slightly rich mixture......so the 130's didn't help at all. Oops! Back to the dealer in the morning.....

[pete]

I got some 122.5's here Rich but probably the wrong type for your carbs... might be just a tad quicker to get them locally though

[BigD_83]

I must say you have some skills, Rich. Looking good.

[Big Rich]

Thanks fellas!

So I made it to the dealer yesterday morning and got some 125 mains. I'm happy to say for the 2 quick little trips I made after installing them, the top end feels much better. Not perfect, but much better. Right now it feels like I should be between the 2 sizes (125 & 127.5), so I might adjust the needle height to see ifthat changes anything.

I'm going for a 2 hour ride this morning after work, and will have a much better idea of how it's actually running.

[pete]

From what I've found so far Rich, with the stock needle it's going to be a compromise...

Either jet for WOT on the main, or jet for mid range on the needle... to get it good on both I think you're going to have to go needle shopping and that's not going to be an easy task!

I've also been able to do a bit more compromising with the mixture screws as well, although at the moment I feel I'm a tad rich on them also.

[Big Rich]

Well, no worries on the jetting today. Took it out for that 2 hour ride (mostly highway), and the air box imploded! Guess it needed a little more reinforcing ...... Oops! Haha...

In the meantime, I have the K&N pod to go back on while I work on the box. One of the benefits of being a parts hoarder.....

[pete]

Oooops indeed! Bummer... glad to see you've got a good backup plan though

[Big Rich]

So this is happening over winter:



It's coming together much easier than I had anticipated. I'll give details when I'm further along though.....

[Big Rich]

Still working out some details, but this is where I'm at:

Front end:The fork spacing and diameter is identical between the GS500 and GS850 "G" (I specify the G model because the GL is different). In order to keep the stock ignition lock and instrument cluster, I will be using the GS850 triple tree in it's entirety (also, the GS500 steering stem is shorter, and the stem swap would require machining the upper part of the new stem). The GS450 stock forks are about 29.5" long, with a tire diameter of about 24". The GS500 forks are also 29.5" long, and a 110/80-17 Avon Roadrider tire has a listed diameter of 24.2". So the change in ride height is minimal. The dual single piston calipers that I ran all season will be replaced by a dual piston GS500 caliper as well. Basically, it will get a Gs850G triple tree and GS500 forks / wheel / brakes / etc, with no loss in performance at all.

Rear end: This is where things get a little bit trickier. Changing from the current 100/90-18 tire to a 130/80-17 tire only raises the rear end by .050", so that's not a problem at all. The swingarm width between a GS450 and GS500 is also identical, so the wheel does physically fit. Obviously there will need to be some fabbing / welding to swap from the mechanical drum to a hydraulic disc brake. The biggest issue is sprocket alignment - the GS500 rear sprocket is 12mm off center from the Gs450's. Late model GS500F front sprockets can be spaced out a little bit with extra lockwashers, and a JT rear sprocket is "dished" (undercut on the bolting surface) - so it can be flipped to move the chain centerline in too. For all the math that I did, the sprocket carrier would still need about 8mm cut back. However, I found out that a rear wheel from a 91-93 Bandit 400 is identical to the GS500 with two exceptions: the rim width is 1/2" wider (17"x4.00" instead of 17"x3.5") and the hub is approximately 8mm more narrow.......supposedly on the cush drive side! I have a Bandit wheel on order, and will confirm all of my fittings hopefully next week.*

[pete]

Good stuff Rich, will be interesting to see how the rear turns out.

Should make it so much better for tyre selection! Do you reckon it'll be quicker steering with the 17" up front? The only time I have issues with mine really is the quick direction changes... the 18" up front and the rake really want to keep it stable.

[Big Rich]

Thanks Pete!

The tire selection with the 500 wheels is much better than stock (18" or 19" wheels). But because the GS5 is an older / smaller bike, it is kinda limited compared to some of the newest bikes. And it should definitely be much quicker steering for me! That dual disc 19" wheel feels massive compared to my 18" wheel, so I would imagine this will be leaps and bounds ahead of that.

[pete]

Excellent Rich, quick steering is good!

[Crow]

Bandit Rear End gs450

Any news on how that bandit rear end turned out?