ideal times for the scrum master to be able to support a teams

The simple answer is as often as needed, and when the developers decide they can fit this into the scrum.  They may wish to include a PBI based upon the sprint retrospective in the sprint backlog in order to ensure that this occurs. 

BTW, scrum is not a methodology, it is a framework.  :-)

What are the ideal times for the scrum master to be able to support and coach development teams to learn the SCRUM methodology?
and how often per week?

Are there impediments to this which have to be worked around? If so, what are they and why?

The Scrum Master should work with the team as long as necessary. There are a lot of factors to consider, including the maturity of the team with respect to working in an Agile (and Scrum) environment, the skills on the team, and how many and what kinds of impediments the team is facing. It's also possible that the Scrum Master is helping the team by working with stakeholders outside the team, helping them to interact with a Scrum Team. I don't think it's possible to generalize when or how often a Scrum Master should spend with a team. 

My opinion is the Scrum Master does this constantly.  It doesn't require a formal meeting or training session to help others understand and appreciate the Scrum framework.  It can be done by simply asking a leading question or suggesting that something be inspected to determine if adaption is warranted. The Scrum Framework provides events with specific purposes all of which are focused on inspect and adapt.  Helping the teams to understand those purposes while appreciating the benefits is one of the responsibilities of the Scrum Master to the team and organization. 

I will also join @Scott Anthony Keatinge in pointing out Scrum is a framework not a methodology.  The Scrum Master has to understand the differences between those two before they can help anyone appreciate Scrum. 

Thank you all for your feedback, i see things more clearly now.