can anyone in laymens terms explain how the cooling system works. history i have just replaced the radiator which was leaking. prior to this i did not drain the system simply swapped one for one. started bike fan working but temp light came on stayed on. on watching bike run noticed water return into top up tank bubbles. is this norm and have i missed something or any test i can do to see why temp light on. good thing radiator not leaking

Les, the radiator is part of a "closed" system. After replacement of the
radiator you filled the system with the fill stubb under the fuel tank?
The cap there has an over-pressure and under-pressure valve. The system
should be filled to the top and the overflow tank about third/half.
Once the bike warms up normally the pressure in the system rises and
some of the liquid (or air if not bled properly) will be pushed out into
the overflow tank. When the bike cools down it will draw in liquid from
the overflow tank. There are instances where the radiator draws in air
when cooling down when the hose between the cap and the overflow tank is
porous.

arrr no still not got tank off so .this means i have to take tank off and find it and refill ?

+1 rene ...good explanation

told you i was a numpty novice but hey so was ronald ragen.

Yep, sorry mate, no mercy!

Now, if you can't find those clips it's quite possible the PO never fitted them back. Quite a few have not got those clips any more and the pins of the tank are just pushed in the grommets at the frame. If you can not find the clips (they should be around the pins from the tank, underneath the grommets inside the little brackets on the frame) just try to pull the tank up at the rear. Those grommets can hold the tank quite tight. Maybe some WD40 or similar on it??

another great sugestion rene ...

dont forget to clean off all oil substances after removal if you want them to last (the rubbers )

maybe something like a wax could help when replacing the tank spigotts in the rubbers ...might give a good easy fit and remooval in the future ..

no clips on it used some force and alot of swearing and up it popped. now to remove. need to get a pipe to stop petrol from coming out so hey you helped me again thanks

one of the tricks is to remember to undo the side covers before attempting to remove the tank ....they do make it hard ...and sad when the clips break off ...

Re fuel leakage, if you have a short length of fuel hose to put on both stubbs (aft is from the pump, forward one is the return) there won't be a leakage problem.

Hi!

On my bike the bottom hose of cooling system is flat if the engine is cold. It is normal, or i must checked anything?

If the engine is hot, the bottom hose is round and hard....

Do you have different level in the expansion tank when hot vs, cold?

The level should rise when the engine is hot, and return after the engine have cooled down.

It sounds like the valves (especially return) in your filler cap don`t function properly, these valves controls the flow forth and back to the expansion tank.

As Inge says, your filler cap is not working properly. You need to look at this as it could lead to overheating due to shortage of cooling liquid.

For future purpose you might want to open a new topic with your questions. For one reason is that you probably get quicker answers in a clearer way, the other being that you don't potentially upset the original poster as he might not have had a workeable answer yet.

ReneZ wrote:As Inge says, your filler cap is not working properly. You need to look at this as it could lead to overheating due to shortage of cooling liquid.

For future purpose you might want to open a new topic with your questions. For one reason is that you probably get quicker answers in a clearer way, the other being that you don't potentially upset the original poster as he might not have had a workeable answer yet.

for the benefit of the uninitiated also, every bit of info helps, so a new thread has a big bold title. ie "look here for the answer to this particular K 100 peculiarity"
because i did not know this. cheers .