Blast nozzle

Hi all last year I  bought an allready built burrell agri.ive just had my steam tests done where the inspector commented on the blast nozzle doesent seem to draw on the fire as he would expect.he suggested making up a smaller nozzle,this got me thinking about what I've read before. My engine started with early kits  under modelworks, where a smaller chimney was supplied. Now it does have the more common  chimney as supplied now.so I've got to thinking has the nozzle sizes changed ?I'd me most interested to hear if anyone has experimented with the nozzle size and what results were obtained, cheers

Can only comment that I own Modelworks engine No 1 which also has the bigger chimney fitted dont think the blast nozzle was changed.

Dont have any issues with draw, BUT do make sure the chimney throat is kept clear, I do remember in my early days of ownership on my 6th or so rally it really struggled to make steam, thought it was coal issues all kinds of thing.
Once home I shone a torch down the chimney and realised there was only about a thumb sized hole left in all the crud to let the fire smoke out
Chimney off, gave it a good clean and the throat area, popped it back on and it was a good as new, I now tend to give that area a good clean every 6mths or so.

Worth checking.

TBH I find the hardest thing on my Agri is trying to stop the dam thing making steam