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Discussion Starter · #1 ·
I have a 1978 Cx500 Standard.

Yes I know y'all already knew that but it is important to say because the procedure may vary slightly for the different bikes. I do not know about the custom, deluxe, or silverwing versions.

I imagine they are all about the same...

To pull the thermostat you must pull your seat and fuel tank. This exposes the top of the engine. Yes my garage looks like crap... I do not intend to clean it any time soon.

Once you have the top of the engine exposed you will want to drain a little coolant out of the radiator so that you do not make quite so much of a mess.

I use the drain plug on the bottom of the radiator for this. There are other methods. You could pull the lower hose, pull the metal tube on the side, cut the lower hose, punch a hole in the radiator... lots of ways but to avoid damage and additional expense I strongly recommend the drain plug.

You do not need to drain much two or three cups will probably do. It depends on how topped off you keep your radiator. Remember this is a small system holding roughly 1/2 of a U.S. gallon (8 cups I do believe).

You will need to remove the top radiator hose before you go much further, might as well do it now. If the radiator hose is stuck on the radiator my favorite way to get it loose is to take a pair of large pliers open the jaws. lightly grip the hose at the radiator and rotate it. Once it has rotated a little it can be pulled off easily. Be careful to not rip the hose, unless you want to replace it.

You will have to unplug two wires. The temperature sending unit and the oil pressure sending unit. You will also have to remove the small coolant line that goes to the water pump cover. They are pointed out in green.

There will be some bolts you will need to remove. They all use a 10 mm socket or wrench. You will find it much easier if you have a universal joint and an extension of a few inches. These are 6-9 ft lbs of torque I believe so do not get too aggressive with it. If it fights remember penetrating oil is your bestest friend in the whole world!

On the left the bolts you need to remove are circled in green. The green curved line follows the upper radiator hose which will already have been removed.

Bolts on the right just like the ones on the left.

I find it easiest to pull out the heat/wind deflector thing now. You need to be careful to feed the wires through it as you remove it. If you just yank on it you run the risk of damaging the wiring.

Once you have the wind thing out you can pull the thermostat body out.

I usually go right because there is no wiring in the way but again things may be different for different bikes.

When it is out you have this

the green arrow points to one of the famous screws that ground the temp sensor and lets you have accurate temp readings. I recommend using a conductive grease (Noalox) on these contact areas, the legs of this brace where they meet the block, and where the bracket meets the thermostat housing. It is cheap and helps a lot!

The two screws you see in the bracket both secure the bracket to the thermostat housing and hold the top of the housing in place securing the thermostat.

This picture shows the thermostat in the housing and the o-ring on the housing top.

Pretty much from here reinstalling is just clean up the mess use a good o-ring. I tend to 'wet' the o-ring with black RTV and reassemble the whole thing. The install is the reverse of the removal. All the screws are 6-9 ft lbs so be gentle.

If I have something wrong or if you want more detail about any aspect chime in!

**** EDIT

I like pulling the entire thermostat housing because it allows me to see the temp sensor and all that. Gives me an idea of if it needs to be cleaned, replaced, or whatever.

Others have said you can just pull the two screws out of the top to get to the thermostat. I never have approached it that way.

The conductive grease I use it is called noalox:

You can buy it at Homedepot or Lowes.

There has been a discussion of if it is conductive or not. I do not care.

It helps protect and improves conductivity in metal joints.

If you walk into Graybar or Grainger and ask for conductive grease they will hand you this or a competitor of it.

I do not use it much in the wire connectors, you can and probably should but just a light coat is all you need. I was mostly saying put a light coat on the contact area between

1) the thermostat housing and the bracket

2) the bracket 'feet' and the engine

That way you have a better electrical path between the bracket, the thermostat housing, and the engine. Better than just the screws.

Like everyone says your mileage may vary. This application of this product makes sense to me but there may be reasons it is a bad idea. I have not found them yet.

The MSDS says the flash point is 310 F so if you get there your bike has much bigger problems than a conductive grease failure!

morrow was kind enough to supply this link

which talks more about the stuff and names what is supposed to be a better one.

I only have experience with Noalox.
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7,223 Posts
Noalox IS a conductive compound used to join aluminum to copper wires and prevent arcing and corrosion (it is required to be used by law when copper and aluminum wiring are joined). It acts as BOTH an electrical conductive paste that will not break down under high current and heat, and serves as an "oxygen barrier" for the aluminum to prevent formation of aluminum oxide (which forms very fast when charged and exposed to moist air.

Silicon based heat sink compound (white paste) is also electrically conductive and I wish I could find more of the stuff, as it seems to have been replaced with nonh conductive crap.

Dielectric grease is NON conductive and used to form an "air barrier" to prevent corosion. When used on electrical connections it is easily displaced to allow the metals to electricall bond.

7,223 Posts
They do use Noalox for rigid conduit threads to keep electrical integridy (not used as a general practice on EMT conduit, only rigid threadable conduit), but its primary purpose is when making electrical connections between aluminum and copper wire in older houses that use that crap (aluminum wire). You can find it at any store that sells electrical (suppliers, Home depot etc).

993 Posts
Gardner Bender (GB) makes a product called Ox-Gard that is conductive. Used for aluminum-aluminum or aluminum-copper connections. I like to use it in crimp connectors before assembling and crimping. But because it's conductive, a little bit will do ya...

GB's product info for it says:

Ox-Gard™ Anti-Oxidant Compound

The perfect safeguard for aluminum-to-aluminum, aluminum-to-copper

wire connections and aluminum conduit joints.

• Guards against oxidation.

• Improves conductivity; penetrates aluminum oxide to maintain

inter-strand and inter-conductor current paths.

• Produces a cooler connection.

Part # Pkg Qty Description

OX-100 1/tube 1 oz Squeeze Tube

OX-100B 1/tube 1 oz Squeeze Tube (blister pack)

OX-400 1/tube 4 oz Squeeze Tube

OX-800 1/tube 8 oz Squeeze Tube
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