Water leak advice

[newfattrixierider]

Nearing completion of renovation on my TRX I have installed a replacement engine after checking compression and valve clearances. These were better than on the engine that was in the bike when I bought it. When preparing to run it for 1st time today after filling cooling system with water I have 2 leaks even without pressurising the system. \ist one is leak from thermostat housing - plastic cap has deformed and not sealing against o ring. Second and most puzzling leak is from a machined hole on the LHS side of the LH cylinder head. I don't even know what this hole is for but my other engine has the same. Any ideas why water is leaking from this hole?

[Mincehead]

The thermostat issue is common, they just do that sometimes. As for the machined `hole` I think you are talking about the drain hole for any water that may get down into the spark plug tunnels. If you`ve got water coming from there, FIRST be certain it`s not residual water from the thermostat leak.
I think it might be.

[Tarwetijger]

I had the same with the thermostat. Not unusual, with only two bolts for a plastic piece that deforms easily.
I fitted the housing together with liquid gasket. No trouble since.