anyone know anything about the mark61, it comes with a moki tuned pipe. i can not find muffler extentions for this engine.

Same as the MOKI .61

Check out the options for the engine at:

www.justengines.co.uk

They are the UK agent for MOKI and are happy to deal with US customers.

I've had this guy for about 5 years, it is an excellent engine, the first one I put on my BTE Venture 60.