Honda CX 500 Forum banner

1 - 14 of 14 Posts

·
Registered
Joined
·
29 Posts
Discussion Starter #1
Hey Guys,

I need some assistance with my cooling system. My main problem right now is with the temperature gauge. The PO said the bike sat for about 3 years before I bought it. He reported the last few times he rode it the temp gauge worked only sporadically.

So far I've flushed all the coolant (it originally looked dark brown and I feared there was oil mixed in - I've pretty much ruled that out now and I don't think it's an issue). I also replaced the thermostat and temperature sending unit. Then, I cleaned the electrical connection at the temp sending unit. After starting the bike up, I let it idle for about 10 minutes and the temperature gauge doesn't budge at all and I don't think the coolant is circulating. It seams like it's completely dead and I'm not sure what to check next. I'm pretty decent with mechanical issues but i'm terrible when it comes to chasing down electrical problems.

I checked all the fuses between the handle bars and the are all fine. Only other clue I can give is that I'm guessing the temp gauge should have a light? There's no light and I'm guessing I wouldn't be able to see it while riding at night.

I would appreciate anyone that could point me in the right direction.

Thanks!
 

·
Registered
Joined
·
1,537 Posts
get yourself a digital infra-red thermometer gun , and then you can test the temperatures that your radiator is getting. Without knowing what those temps are you are just guessing.

The temp gauge may well have decided to die. Its not uncommon on 30 year old motorcycles. You may be able to source another gauge from Ebay or via the classifieds here , and then compare the actions of those gauges.
 

·
Registered
Joined
·
964 Posts
I am not sure how one can know if the coolant is circulating or not..but Im no expert...lol
Either way, if it is in deed not circulating..couldn't the problem then also be with the water pump?
 

·
Registered
Joined
·
24,172 Posts
the cx650 has no 7 volt regulator

lift the tank and pull the wire off the temp sensor make sure it remains plugged in to the harness wire

ground it and turn the key on

the gauge should go to full hot if it does your sensor is shot

if the oil light comes on the blue with red trace from the oil sensor is plugged into the temp gauge wire

reverse them so they are blue red to blue red green with blue to green with blue

if that is ok and the gauge does not move then some po has probably left the wire unplugged in the headlight or it has

become separated i think if i recall its a green with blue trace but you will see as it is the same one as the temp wire

it some times gets confused with a green ground
 

·
Registered
Joined
·
6,510 Posts
good to know. The GL650 still had one. mine went bad

Nolimitz - My understanding is the 650s don't have a 7v regulator.



Sent from my iPhone using Tapatalk
 

·
Super Moderator
Joined
·
13,796 Posts
Do you know how to test the water pump?
The water pump consists of an impeller attached to the rear end of the camshaft and located inside a shaped cover. Almost any of the things that could prevent the pump form working would result in a large puddle below the bike so chances are the pump itself is working.

(see image below) When you first start the cold engine the thermostat is closed so coolant can only flow through the heads via the water pump and the bypass hose. When the engine warms the coolant sufficiently the thermostat opens, allowing hot coolant to flow into the top of the radiator and cold coolant out of the bottom of the rad, through the water pipe and into the water pump.

To determine whether the coolant is circulating feel the water pipe on the left side of the engine. It should be cool at first and should become warm to the touch once the thermostat opens and the hot coolant makes its way through the rad (usually a couple of minutes).

 

·
Registered
Joined
·
1,637 Posts
To test for coolant flow.Take the radiator cap off while cold, start and watch for movement inside the neck (must be full), might have to warm up.Water pump impeller might have become disengaged or thermostat is stuck closed.Alt. method is to see if top of radiator gets hot but not as accurate.Edit I see Bob 's post went in while I was typing but I will leave mine in as it's a little different.His is good though, the picture is very good ..
 

·
Registered
Joined
·
29 Posts
Discussion Starter #11
Okay, thanks for the guidance guys. I'll post an update after I have a bit of a chance to look at it this weekend. I've never had any coolant leak through the weep hole but I need to make sure it's not plugged as well. If it's not plugged, I'll assume (for now) that the impeller is properly engaged.

I did put a brand new thermostat in but running the bike last night for about 10 minutes, the water pipe on the left side of the bike didn't warm up at all. Although, I can't remember if I checked the coolant level again after I filled it back up. Hmm... I'll probably need to pick up an infrared thermometer as well like muzza suggested.

Definitely some good points to think about and look into. Thanks for the help!
 

·
Registered
Joined
·
4,278 Posts
[OT]

A good or bad example for a not working waterpump.
The steel shaft with the splines etc. for the impellor was broken.

NoWe abriss-bruch.jpg

But another defect is possible that the splines inside of the impeller are kaputt/damaged.
The effect is: The cam turns but not the impeller and the hat cap nut plus the copper washer can't turn the impeller.
[END of OT)

Sorry this is just an example when the engine gets too hot. :(
 

Attachments

·
Super Moderator
Joined
·
13,796 Posts
An infrared thermometer is nice and can give you accurate numbers but we figured this stuff out for a long time before they were invented by feeling the parts in question with our hands.

Just idling a bike may not actually warm it up properly, even after 10 minutes. Check that the rad is full (when the engine is cold, of course) and take it for a ride around the block. You should be able to pull away within 30 seconds of starting it and you should be able to open the choke (button pushed in) within a minute of pulling away. By the time you get halfway around the block the water pipe should be warm.

If it isn't there are 3 possibilities:
1) The thermostat is installed incorrectly (I don't think it will fit upside down but you never know)
2) The thermostat is defective (do the boiling water test shown in the FSM)
3) There is a blockage in the cooling system that is preventing flow.
 
1 - 14 of 14 Posts
Top