jeez, i'm old enough to be your dad - easily i too like jenning's book, i think it's a great read and not as difficult to take in as graham bell's book . but like you say, they were good for the 70's. there again, the most modern 2 stroke i've worked on was an 86 rg250 gamma engine, but after stripping the engine completely, apart from being watercooled, it wasn't much different from the gt250's i usually work on
modern 2 strokes are so complicated now [to me] and they've wandered too far away from the simple piston port 2 stroke of yore. i'll stick with the gt250's, they don't tax my brain too much
right, the gt350 i'm building. i had the heads milled out to 65mm diameter [supposedly], fitted a 0.5mm thick copper head gasket, annealed it and finished building it. result? absolutely impossible to kick over. after taking the heads off again and measuring them - should have done that first in hindsight - the left one was only 63mm diameter, so that needs addressing. after measuring the volume of the head minus the volume of the piston dome and doing the maths, it seems i've got 16:1 compression ratio, which is somewhat high
i'm sending them back to the bloke that milled them and he can first of all take them out to 65mm, slope the squish down to the original inside edge and take 2mm depth from the combustion dome. this should take me down to a more reasonable 8.8:1 c/r. that, of course, is when i can get hold of him until then, i'll try and figure some other way round it, but at the moment, this is all i can think of to lower the c/r considerably.cheers, dd.
courier picked them up yesterday morning, so should be up north by wednesday - in theory. first job he's doing is drawing me a before and after cross section, just so there's no mix up with my instructions 
what a plank 
