That's the autochoke end nut that looks like it is going to come off.
I am not sure why there is oil there. Should be engine coolant only. Maybe it is rust mixed with coolant leak.
Or maybe the thermo element fluid for expansion function inside the
autochoke. If it is engine oil getting there via your cooling system, then it is a
very serious thing.

Better get it repaired, if it comes off during driving, coolant will leak away leading to engine overheat.

I got it wrong, it is the drive shaft, as seen in tacra blog.. Will change it after CNY, thanks!

Just managed to changes Michelin XM2 Tyres. Any review on this tyres guys?

Notice difference on rainy season on evenings currently. It does not slip easily & less hydroplanning.

any user 4g13 carburetor change to efi(fuel injection)

pls advise if this can be done and how?

price?

wah ...still can get 100 ????

i bought like 160+++

Look at PIAA Night Tech bulbs. Am using now. Much brighter than stock.  Ps : I'm not a salesperson.
http://www.piaa.com/store/p/34-H4-Night-Te...ogen-Bulbs.aspx

If I am not mistaken, that part is some sort of a thermal expansion device using the coolant temperature to move the throttle and also to alter the mixture, as part of the autochoke function.

1) Are you loosing coolant? (Looks like there is a hole when the nut broke off).

2) Is your engine running rich?

If so, there are repair kits available see  example below

The danger is that the coolant will shoot out of the exposed hole when the
temperature & pressure rises, but since your coolant level is ok, the remainder  of
the plug seems to be holding. But better have it checked / repaired because if 
you suddenly lose coolant, there will be overheating and subsequent expensive
damage to engine. Are those leak marks (photo below)?

Yes, rich means too much fuel in the air-fuel ratio. That will result in poor fuel
economy, soot at the plugs, poor performance .... I was suspecting that the
missing plug will interfere with the autochoke function....

Engine pinging (or "knocking") is pretty common amongst Iswaras. Yes, you could go have your ignition timing checked and retarded a little bit. But engine pinging is not all the time due to wrong ignition timing; carbon deposits left in the ignition chamber do contribute to the problem significantly too. My own experience is a case in point:

Had my ignition timing checked and tuned a year back. Few months later, engine ping came back. What I did was use a fuel system cleaner (Techron Concentrate Plus) and fuelled up with several tanks of Caltex fuel. Engine ping went away after the fifth tank of petrol. I guess its the PEA (polyetheramine) in Techron that is really effective at cleaning the gunk out. You may try it for yourself too.