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Discussion Starter · #1 ·
Hey all,

I am working on a 1979 cx500c. I bought it from a kid recently who told me that there was a temperature issue. He said he was told that it was a mech seal issue in the water pump. I check the engine oil, it all looks brand new. There doesn't seem to be any coolant leaking into the engine or anywhere at all for that matter. I took the thermostat housing off and replaced the gasket. The reservoir was full, again...it doesn't seem to be leaking. I took the thermostat out of its housing and checked it. It fell open at about 160 degrees or so. I took a peek into the radiator and it could use a flush, but it shouldn't be impeding it that badly.

Today, I started her and let her idle in the garage. Once she gets warmer, the needle on the temp gauge cruises straight into the red. It doesn't take long for it to get there. Only five minutes or so. I had a infrared temp gun. When the temp gauge hit red the cylinders were reading between 155 and 165. The return tube on the radiator never got higher than 125. What's the deal? Can anybody help me out. I have a good understanding of motors in general, but I am all self-taught. Any help would be greatly appreciated it. Teach me, friends.
 

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I am siding with CXPHREAK The sender, gage or 7-Volt regulator. likely the issue. Did the PO add any accessories that may be attached to the regulator wiring? The temps you mention seem pretty good.
 

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Discussion Starter · #5 · (Edited)
No, the PO had the original gauge cluster on the bike, but I plan on putting a new gauge cluster on the bike anyways. Would new gauges come with new sending unit or adapters? Would replacing the gauges circumvent this temp gauge issue? This leads me to another question... I plan on placing some mini plain-face gauges but have not found one with a temp gauge in the tach. Could I avoid this issue by getting a rad cap with a built-in thermometer?
 

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I thought my bike was overheating a while back, then I realized a wire had fallen off the 7 volt regulator. Maybe a ground wire, if I remember correctly. Put the wire back on and the temp gauge dropped.
 

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Find the 7 volt reg, make sure the black and green wires are connected and disconnect the yellow wire. Turn on the ignition key and check what voltage comes from the yellow wire using your multimeter set to 20 volts DC. If you get 7 volts the regulator is good. Anything higher and it's not.

As Ozandy says, if the unit is not earthed you will also get 12 volts coming out of it.
 

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Lots of ways to do a temp gauge that are practical and visible.

Some people have a hard time getting the stock cap off .

Why put 1/2 way under the tank?

Might as well leave it off and listen for the cap to scream or spit hot coolant

on your leg or just watch your mirrors for a huge amount of white stinky smoke.

Then you could let it cool off refill it to limp it home and hydro lock it.

You may get lucky and puke anti freeze on your rear tire,just as the engine seizes.

Makes a great traction compound.

There so many better options.

There are after market gauges Electric and Manual that can go in the stock sender location.

There are radiator hose in line kits.

In the end its yours,so no need to pay any attention to me.
 

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The stock sender will in fact work with most aftermarket instruments as modern replacements tend to be 12 volts. If replacement is 7 volts you have come full circle. ;]
 

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