RC390 Overheating

[MuTToN_DaGGeR]

Hello all.

So Ive had my 2015 RC390 for a few weeks now.

I bought it second hand with 30K Km's on the clock.
When I bought it the previous owner told me that it got hot and cut out, I decided to go ahead and purchase it with this issue.
The first thing I did was pull the water pump housing and replace the OEM bolt with a locking nut and thread locker, throw coolant in the bike and torque it to 10nm.

It was fine for a few weeks but today the bike overheated just as I got home, bearing in mind that its 11 degrees Celsius today.
I wasnt riding it that hard, nor was I in much traffic, I cant understand how this can still be an issue?

I felt the radiator when I got home and the fins were cool and the sides of the rad were warm, the engine on the other hand was blistering hot.
I know this is a common issue but I cant seem to find a thread that has a concrete fix.
When I changed the coolant it was the correct colour, so there cant be a gasket issue, the pump spins as I did a few cranks with the cover off to check this.

Please please please could someone recommend a fix here?
Im at the point where I might just flog the bike as this was supposed to be the daily driver.

 

[ReidMcT]

Sounds like a bad thermostat.

 

[John390]

it certainly could be a bad thermostat.

It could be an air pocket in the cooling system too, especially since you had it open. I am not sure about the bleed procedure on these bikes, so if its not just a "fill it and forget it" thing, it can be tricky to get all the air out. In cars that don't have easy bleed procedures it can be tricky to get all the air out.

Also it could be a plugged rad. Cold parts and hot parts on a rad are often indicitive of this.

Does the fan come on when its supposed to?

Also are there any fan mods done? I know the older bikes have crap fans

 

[Andy]

Sounds to me like possibly the thermostat.

Re. Bleeding, bleed screw is on top of rad, undo and slowly top up radiator until it starts bubbling out then nip up. Caution as with other nuts and bolts the bleed screw is also made of cream cheese so don't go mega tight!

Then ensure radiator is topped up to base of neck, rock the bike to and fro to allow air to come up, if you can lower it as low as possible. I then let it stand to allow air to rise, give it a run up a few times too. Finally top up the overflow bottle to line, put on high pressure cap and enjoy.

I also did this once I fitted my Samco hoses.

Sent from my HUAWEI M2-801W using Tapatalk

 

[MuTToN_DaGGeR]

So I now know what the issue was.

The head gasket went and was pumping air into the cooling system.
There was obviously a constant pressure build up from the blown gasket, pushing the coolant out of the rad, overflowing the overflow and not letting the coolant flow back into the radiator.

So if anyone else has the below symptoms, change the clearly faulty head gasket.

• Pressure release while opening the cap when the bike is cold.
• Constantly "overfull" overflow tank.

I hope my issue will save someone else a completely gaziboed motor in the future.