TOPIC:

Hi,
I charged the battery overnight and it charged Ok. When I go to start the bike it turns over (only just) like the battery is flat. Any ideas where to start troubleshooting?

Regards
Yaegunp

The earth lead where it bolts to the engine can cause this when it has a bad connection.

An easy way to eliminate a bad battery and problems is to jump start it connect the earth at the battery then direct to the engine and see if it makes a difference.

UPDATE: The Starter relay/solenoid is smoking and frighteningly hot when trying to start. (8 seconds max)

The engine turning over slowly is the reason the starter relay is getting hot. When the starter motor turns slowly it draws a heap more current, more than double at times so it is quite likely the relay is passing 150 amps and maybe even more. It is probably cooked and should be replaced because it will give trouble in the future by the contacts welding together.
You need to investigate why the starter is turning slowly it can be many things but usually is a problem associated with the engine being tight. I would be looking for tight bores caused often by gummy residue build up in the bore and piston rings. Put some light machine oil down the plug holes and turn it over by hand then let it sit for a few days. there are many other things but usually associated with poor assembly of the engine. Have a look around and do what you can without a major tear down.

In "theory" the relay which is a mechanical switch should be capable of carrying more current than the demand of the circuit. When the relay is new this is not a problem but after a number of cycles ie. starting the bike, the contacts in the relay start to pit. The more they pit, the higher the resistance becomes across the contacts. The higher the resistance the more heat generated at the point of resistance. Hence the reasoning behind only cranking over for a certain length of time and then allowing all the areas which got heated up, a chance to cool off before continuing. This is especially true for the slip rings on the starter rotor which are soldered to the windings in the rotor.

As the saying goes with old mechanics "You let the smoke out of the wires" so at the very least the relay will need to be replaced. But RickG may not be wrong in saying you've developed a high draw in the circuit. If the engine is tight for whatever reason, the starter circuit will have a high draw and an old relay will sacrifice and pay the price. Also, if the slip rings and brushes in the starter have not got decent contact, there will be a high draw in the circuit.

I would start with a new relay and after installing check the draw on the starter circuit. Chances are the relay needed replacing and you'll be fine but don't overlook the possibility of another problem that may have smoked a weak relay.

The solenoid when activated, pulls down a heavy copper bar across two equally heavy contacts thus completing the high current circuit to the starter motor. Cranking the engine over for "lengthy" intervals in an attempt to get an engine running will create high surface temperatures on the starter-relay contact areas. Arc-pitting, corrosion will eventually result in no power at all to the starter-motor. Intermittent starter operation can be a result of many hits of the starter button which will literally "hammer" the corrosion/pitting down enough to make electrical continuity. However, with the contacts surfaces now already damaged, corrosion and further pitting will continue to create intermittent(and high resistance)starter operation to a point where electrical continuity is no longer possible no matter how many times the starter-button is pushed. I had this exact problem many years ago. Eventually the relay would activate (click) but no power to the starter-motor.
(The starter-relay is easy to disassemble.) I cleaned the damaged contact surfaces and "brazed" some silver (high conductivity-low electrical resistance/better anti-corrosion properties)to these same areas. I filed and polished the (new silver) contact areas flat and smooth and this "fix" has lasted about ten years without any further problems. On the other-hand I have no Carb/fuel/ignition-system issues so the solenoids internal-contact time from "push to run" is merely 1 to 2 seconds. This is not significant time to build any damaging heat or related problems to the contacts of the relay.