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1978 CX500, Deceased 63 Matchless G12
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Discussion Starter · #1 ·
Hi there, I am slowly gathering bits for my bike and would like to know if anyone has an idea of where I can find a front Rotor and calipher and associated bits to turn my single disc 1979 CX 500 Std into a twin disc set up?

Thanks
 

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I have for sale the original Comstar (not reversed) front wheel. I replaced the hub with one for a dual-disc setup. Everything, including the 35mm (1,350 inch) forks works great and I ran it, leak-free, for about 5 years until I replaced it with a front end from a GL 650 to get 38mm diameter fork tubes. The setup will need brake calipers, discs are mounted.
The matching 18-inch rear wheel is also available. Pictures should be somewhere on this site. I think it looks so much better than the 16-inch rear wheel and because a larger outside diameter tire is available for it, it will shave off some RPM's.
With the 18-inch rear and the 650 clutch mod I lost about 1000 RPM at speed, or the equivalent of a sixth gear.
Price is negotiable as I would love to see it go to someone who appreciates it. The existing yellow paint is a good, hard, catalyzed urethane and would make an excellent primer for your chosen topcoat. Both wheels have excellent tires that I can either ship or keep.
Capt Frank
 

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1978 CX500, Deceased 63 Matchless G12
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Discussion Starter · #3 ·
G'Day Captain,
My current wheels are also original Comstars in 18inch, though I am not sure why the bikes were only supplied with single discs here ins Aus. The Discless fork has all the mounting lugs, so I would just need to find a single caliper and disc with the brake line splitter . Appreciate you response though
 

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'84 CX650E that is evolving into a GL500
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Are you sure it didn't originally have a second disc & caliper? 43 years is a long time and it wouldn't be the first bike we've seen here that was converted from dual to single disc (mine, for example). And the parts drawing at CMSNL shows 2 discs.

Welcome to the forum. Please add your location and your bike's model and model year (NOT year first registered as if that's what the paperwork shows) to your profile so that you don't have to remember to tell us every time and we don't have to keep asking when you forget (see Forum Settings link in my signature).

And welcome to the world of antique vehicle ownership (they own us, not the other way around). Your bike is about 4 decades old and may or may not have had all of the maintenance necessary to keep it safe & reliable so it is highly recommended to download the Factory Shop Manual for your model (available through the CX Wiki - link in my signature) and go through all of the service procedures, regardless of whether your bike has reached the specified mileage.
I also recommend looking on all rubber parts with suspicion because rubber does not age gracefully. Check the date codes on your tires and replace them if they are over 5 years old no matter how good they look & feel (old rubber simply cannot flow around the irregularities in the asphalt well enough to grip, especially if it is cool or wet). If your bike still has the original rubber brake line(s) (should be replaced every 2 or 3 fluid changes = 5 or 6 years) I recommend shopping for modern stainless braided ones (they last practically forever and double the life of the fluid). And don't forget things like the rad hoses and the boot between the engine and swingarm (they can crack on the bottom where you don't see it).
 

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Twin discs came here in 79 or 80. 80 models definitely had 2 discs but I have never actually seen a 79 CX so can't really say if this should have 1 or 2 discs.

Anyway, the parts should be readily available in Australia. Lots of 80s and 81s here and the twinpot brakes used on the 82 are a direct fit.

CB750/900 brakles also fit.
 

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1978 CX500, Deceased 63 Matchless G12
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Discussion Starter · #7 ·
Greeting Sidecar Bob,

Bikes Vin Plate shows 06/79. so it is a 1979, although going by the Engine number which starts with cx500-202..., it should be a "78, go figure.

I have restored a few old British bike in my time and few Italians as well, so hopefully my first Japanese re-build will go easy enough.

CSphreak, I think I saw you on the Aus forum as well. Hopefully I will find parts closer to home, although as we know, Perth is not close to anywhere, even in Aus.
 

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'84 CX650E that is evolving into a GL500
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Dates on VIN plates in that format are usually the date of manufacture, not the model year, although a June manufacture date is most likely within the model year. (Most bikes we see here in North America are actually manufactured in the last quarter of the previous year - they do that so the distributors & dealers can have stock in time for the winter bike shows).

It isn't uncommon for bikes this old to have had their engines replaced but the page linked below doesn't show any engine numbers starting with "CX500-202..." for any year, Are you sure you typed that correctly?
 

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1978 CX500, Deceased 63 Matchless G12
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Discussion Starter · #11 ·
my number is...
cx500-2050975..

Compliance plate 06/79



so based on the above, it is a 1979, though not sure when the serial numbers change to the next model, which is the CX55Z with engine numbers starting at CX500E-2100000.
 

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1978 CX500, Deceased 63 Matchless G12
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Discussion Starter · #12 ·
Pretty much the same as this one..
Wheel Tire Vehicle Automotive lighting Automotive tire
But heaps more corroded and tatty.

Its is currently sitting in the garage feeling very naked,with just the wheels and motor in it. I have to replace anything rubber as it is either cracked or rock hard. Will be doing a mild Cafe racer. It has a nice little mini fairing that cam with the bike, very 80's. 18 inch wheels rear and 19 front.
 

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1978 CX500 "The Grub", 1983 GL650I "Nimbus"
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Here, a '79 Standard would have the larger, flat turn signals, a square master cylinder, gold highlights rather than silver, and be missing the plastic rivet covers on the wheels. Otherwise identical to the '78. I don't know if the serial numbers started a new sequence.
 

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1978 CX500, Deceased 63 Matchless G12
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Discussion Starter · #16 · (Edited)
Or maybe when it left the warehouse.
Either way, I am sure we can agree , its an old bike from somewhere between 78/79 and need a fair bit of work. Doesn't help with the query of finding parts to upgrade the brake, as I have now heard that just about every argument pro and con about changing fork size, rotor size, wheel size etc. Will quietly do some research and hopefully be able to upgrade the forks and triple trees to get what i want in there one days after i have redone the rest of the bike.

I will sell off all the discarded bits as I am not restoring, going for a soft cafe racer style.

Happy days
 

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'84 CX650E that is evolving into a GL500
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As has been mentioned, there are some differences between the model years so it is best to go by the year that the serial indicates it should be regardless of what the paperwork shows.

BTW: The best advice anyone can give you about customizing any vehicle is to get it safe & reliable in more or less original condition and use it for a while before you start making any changes so it can tell you what changes it needs to make it do what you want/need better. That approach almost always results in something you actually want to keep and use but making changes based on style or on what someone else (who may or may not really understand how the changes affect the way it works) has done often results in a piece of expensive yard art that you can't stand sitting on for more than a few minutes and might even be dangerous.
 

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I can’t help you in suggesting where to find the parts that you need. However, I might be able to provide you with an approach to widen your search.

Given that you believe that bikes in and around your year could be supplied with either a single or dual brake setup, determine which way you want to go; two large rotors or two smaller rotors.

Around 2008, there was thread by SpaceTiger in the previous ChopperCharles forum on how to upgrade a Silverwing Interstate to use two of the larger naked bike rotors. The author provided part numbers but more importantly, the approach they took. A key finding is that the left leg of both the naked and the Interstate were the same part number. Same with the left brake caliper. So they deduced that the only difference had to be the mounting bracket between the fork and the caliper to position the caliper relative to the rotor size. Now the real sleuthing started; what other bikes shared the same part number as the naked bike left caliper mounting bracket and more importantly, did those bikes come with dual brakes. It was assumed that left and right leg setups are virtual mirror images of each other. Once that was determined, one could now know the part number of the right leg bracket and more importantly, what bikes it fit and search eBay or other places for the desired brackets.

I’m assuming that your CX followed the same rule; larger disc for a single than fitted on the dual setup. So you are at a crossroads, which way do you want to go, two large or two small discs? In the case of going to the smaller discs, you just need to look in the parts book for your bike and find the part numbers for the left/right brackets, left/right rotors and right brake caliper. Find other bikes that share the same part numbers to widen your search and have at it. Brake calipers will be the most commonly shared component. If you want to go with bigger rotors, you will need to find dual brake bikes that share the same part number as the single disc bracket fitted to your CX.

Note, you will need to see if the front wheel thru bolts that hold the rotor in place is long enough to allow the thickness of an addition rotor. I found in my conversion that Honda used bolts that were just right, with very little thread showing from the nut and I needed to find longer bolts.

A brake line splitter is not absolutely necessary. I’ve seen mention of running a brake hose directly to one caliper and then running a second hose from that caliper up and over to the other side, stacking the banjo fittings on the one side with a longer bolt. Or running two lines from the master cylinder, one for each caliper and stacking the two lines at the master cylinder.


Greg
 

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'84 CX650E that is evolving into a GL500
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Some pics of the bike could help us figure out whether it has a single larger disc or (as I suspect) it came with two smaller discs and one has been removed.
 

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I converted my 1979 CX500 to dual discs by using the front end from a GL500i. The GL500i discs were smaller than the single CX500 disc, so I then upgraded the GL500i front end by using 2 of the larger cx500 discs and caliper brackets from a cb750 to move the calipers further out with the larger discs. Made the front brake almost touchy.
 
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