I have found and fixed the issue with the high idle. The bush that the governor spring centers on was installed backwards. Correcting this I have been able to adjust the idle to around 565RPM.
Regards
Phil
944A - Machine SN 43A2589 Engine SN 90A284
955K- Machine SN 71J3772 Engine SN 83Z0704
D6 SN's 4R732sp, 5R2724, 5R4832
D8 SN's 15A1254, 15A2287, 15A2723