Yard-Man over heating

[flattop]

Until recently I knew nothing of mechanics or mower repair but since I bought this yardman secondhand I have had to learn a lot! However everytime I have a new problem I am lost. Recently had a leaking head gasket, which has been changed but now the engine seems to be overheating after about 10mins of running. It smells hot and there seems to be a bit of smoke coming from around the front of the engine. I also think it is running too fast and that the throttle is not properly returning to its low point. There is no oil or engine temperature gauge.
It is an MTD Yard-man TF4130, made in Canada but bought in France, and I think it dates back to around 1999 -ish.
Does any wise person out there have any idea what the problem is?
I have put so much work into it and learned so much I really want to get it going and clear the jungle that used to be my garden! Help!!!

 

[EngineMan]

If you can post up the engine and model number someone on here should be able to help you.
If the airways are clean and the oil is right, it maybe running a little too (lean) has for the running a little high on idle, a lot of them do seem that way.

 

[flattop]

The model no.of the mower is 136N473F643, serial no. 2K165/1-0060; It is a TF4130. 13HP B&S motor, Model no.28/1707, Type 213601, Code 95106ZA. Airways seem to be clean and filter cleaned recently. Oil at correct level. Thanks.