I've lust finished and run the Duclos 'Topsy Turvey'. It is an excellent runner but wants to jump up when it fires.
Any suggestions for a fix? The compression seems very high, is that a possible problem?
I'm no expert, but high compression would be my first guess for your acrobatic engine.
The main thing is that you got it running in the first place. Congratulations on that.
To lower the compression ratio you could put a thicker head gasket in as the simplest solution. Perhaps shave a bit off the crown of the piston if there is any spare metal there. Probably the most drastic way would be to make a new shorter con rod.
