squish band

Trevor
After such an exciting meeting and looking at dereks bike and some of the bits i bought and love the
ingenuity of Nigels project. brought a couple of questions up in my mind.
1. benefits of flat top piston over dome in relation to swuish and the machining of the head?
2.Whats the maximum over size that can accommodated in original 125 pot?
3.Is there any merit in removing all the fins on a standard 125 and getting new aluminium fins cast on, improve cooling?
4. is there any sense in fitting a reed valve to an early barrel?
5. My barrel and piston are 54 bore and 56.5 stroke presumably this is due to the rod of unknown origin? looks like a alfa?
6 to try and make life a bit simpler as the piston is a mystery would it be best to build a standard engine to start or do a Nigel and go the whole hog and
bear in mind I have lots of enthusiasm and a small budget!!
thanks Mike

Mike,
So pleased that you enjoyed the get together, these things are always a little fraught and slightly chaotic but always low-key, friendly and at times downright comical!

On page 2 of the forum is a post entitled…… Flat tops or “Ds”… the conversation in those articles should help with the questions you are asking concerning piston crown geometry.
Hand on heart, it has been so long since I have worked with a barrel such as yours that I can`t accurately say how big an over-bore would be safe. Installing a liner is another matter of course.
An easier option for improved cooling is to remove the top few barrel fins and shrink on an aluminium ring of larger diameter fins. Casting sounds extreme and pricey and probably contravenes the club rules.
A reed valve will improve any Bantam engine, but it has to be done properly as an integral part of a design package. It will of course allow a third, rear transfer port to be installed and that alone can provide for a nice performance hike.
Your bore and stroke combination is slightly unusual, but absolutely fine for that, I`m not sure about the con-rod however, but it did look Alpha, so 125mm long, not ideal but it is what you have.
One thing is for certain you won`t have an easy time trying to emulate Nigel`s achievement, even Nigel isn`t having an easy time, but he will succeed, he has that sort of determination! But isn`t that a wonderful piece of alternative thinking and execution from a clever, free thinking mind and skillful hands!
Check your PM box later today!

Trevor