VW syncro forum – forum for VW’s syncro vehicles, mostly golfs but other syncro vehicles too
VPerformance – couple of bonnie scottish lads who run a youtube channel and website with lots of helpful info on DIY remapping. They seem to be mostly VAG-based.
Scootershack – awesome automatic scooter forum (mostly UK-based)
Steady Garage – some very cool and handy parts for custom scooter conversions. Superbly helpful too as I found out recently.
Pedparts.co.uk – spares and tuning parts for scooters
Adrenalin-Pedstop.co.uk – more fun bits for scooters and mopeds
Yamaha C3/Giggle/VOX fatty conversion – basically the only other person I’ve found doing fatty conversions on yamaha. Awesome build!
Misc useful tools:
Cylinder compression calculator (in german)