I at last have a pair of exhaust pipes for my T300 - non original in copper but not bad and certainly better than nothing. Fitting them reminded me that I had not managed to get a very good valve seal when I assembled this engine over christmas a couple of years ago - despite apparently good valves and seats freshly ground, compression was weak with an audible hiss from the exhaust ports when turned over slowly.
I thought about taking the heads off again to investigate, but laziness got the better of me and I decided to see if it would go. Bit of a pig to start, probably due to the low compression, but once going it roared away merrily. As it was just sitting on a board (laziness again) I had to hold it down to stop it escaping onto the lawn, so I was forced to bask in the exhaust noise and gale from the flywheel fan for the duration.
After half an hour or so I closed the fuel tap and waited for peace to break out, and waited, and waited for so long that I began to suspect that either the fuel tap leaky or I had discovered the 'perpetuum mobile', but eventually it stuttered to a halt. Compression was now much improved and I couldn't hear any leaking into the exhaust, mind you I couldn't hear much else either!
Still not quite right, even without a silencer these engines are usually fairly inoffensive off-load and the heads seemed to get hotter, quicker than I would have expected with the mighty wind blowing upon them so I suspect the ignition is somewhat retarded (the magneto coupling disc is a rather mangled affair someone has 'crafted' out of canvas belting). Also it won't run unless the choke is almost closed - anyone know what the correct jetting is for the Solex 26 FH?