Hi guys.. correct me if im wrong but this is my thermostat yes?? My cooling fan is on from cold which it never was before.

I installed a lanyard kill switch when i got the bike so removed all the headlight and associated wiring.. however the bike had been running fine for long enough.. now all of a sudden ill get going and when the bike gets hot itll just stop.. not splutter as if it were fuel related..itll just die. Ive checked and replaced the spark plug.. could it be the earth on the  kill switch be no use as its shared with thr coil earth and not getting a proper connection?

Yes i leave it for 5 mins and it fires up.. i tested the thermostat in boiling water but no movement on it at all. 

I take it when you test it in boilingbwater it should open and close aye??

gassertxt, you are correct. If you start the bike, let it idle the fan should start and after a while it should also turn off. If this is not how your fan works there is a problem. Typical problems are thermostatic switch, water pump impeller, and low coolant level ( this is probably not the case on this bike as the thermostatic switch is located at the top of the radiator )   Good luck.

When testing a thermostat (or any other switch that controls a power supply) just using the resistance setting on a meter is not always reliable. Use a battery and something of similar wattage to your fan motor.

Generally when testing car components  use a 12v battery and a combination of bulbs.

I suspect your problem is a missing ground. The kill switch wire comes from the trigger circuit of the CDI and shorting it to ground stops the sparks. The fan drive circuit comes from the lighting coils through a rectifier (changes ac to dc) and I think a voltage regulator (zener diode that clamps voltage at a certain level) The two circuits should be completely separated. What can happen is the two share a common ground point. If this ground point is lifted because of a loose screw or paint/anodizing/corrosion on the frame then the two circuits become connected through the common ground point. So if you have a defective kill switch (not uncommon on a Beta actually sorta expected on a Beta) it could short out when the thermostat comes on and it will stay shorted until the thermostat switches off. It's also possible you have inadvertently connected the hot side of the kill switch into the hot side of the fan. This could blow your CDI up so it's important to fix this immediately.

First thing you need to do is make sure the circuits are separate. Find the hot wire for the kill switch which is typically black/white and make sure it only goes to the kill switch. Take the return wire from the kill switch and attach it to a hard ground on its own. I run mine back through the harness to a mounting screw on the ignition coil.

Next make sure the ground connection for the fan circuit is making a good ground contact. Scrape paint/anodizing to get down to bare aluminum if you have to. I'll usually add a drop of silver filled thermal paste used for CPU coolers just to prevent corrosion and silver is the most conductive metal (mini geek-out there). A high resistance ground on the fan circuit can mimic all kinds of issues including a weak fan or a bad thermostat.

Once you do this I think your problems will be fixed. At least with your thermal kill switch.

Edited June 18, 20179 yr by dan williams

I've done this before as Oni Nou and others have said you have the connections wrong. Trace the wires from both state and kill switch. 

Gentleman thankyou all very much for your input, finally the gasser is back running as it should... fan coming on as it should rather than all the tine and kill switch working spot on.

My final issue was trying to get the correct wiring schematic but one of the other guys provided me with that and within 10 minutes we were firing.. 

Thanks again chaps ✌??