KTM 640 Rally Engine Rebuild – Bottom-End, Kickstarter & Gearbox Step-by-Step (Ep. 5)

🏍️ Welcome back to the KTM 640 Rally Bike Build Series! In Episode 5, we take on the engine bottom-end rebuild, showing every step from disassembly to full reassembly. Perfect for anyone restoring a KTM 640 LC4, building a rally bike, or learning detailed engine techniques. 🔧 What’s in this episode: Kickstarter shaft assembly & seal replacement Shift forks & shift drum installation Pretensioning the kickstarter spring Gearbox assembly & installation Crankshaft installation & case assembly Handling tricky moments like a snapped oil jet ⏱ Timestamps for Quick Navigation: 00:00 – Introduction & episode overview 00:10 – Rear tanks & frame update 00:20 – Kickstarter shaft assembly layout 00:35 – Cleaning engine parts 00:38 – Replacing the kickstarter shaft seal 00:43 – Reassembling the kickstarter shaft 00:56 – Using assembly lube 01:00 – Installing the kickstarter shaft assembly 01:10 – Gearbox installation 01:27 – Rotating the engine stand for gear selectors 01:50 – Installing shift forks & shift drum 02:05 – Fitting shift fork shafts 02:30 – Installing dowels for the shifting mechanism 02:48 – Mounting the shifting mechanism & torquing bolts 03:10 – Mounting the shift lock before final torque 03:35 – Shift drum locating device installation 04:00 – Replacing O-rings before shift shaft installation 04:05 – Sliding in the shift shaft 04:15 – Pretensioning the kickstarter spring 04:25 – Testing the kickstarter return 04:35 – Installing mainshaft O-ring behind bearing race 04:50 – Crankshaft seal installation 05:10 – Hammering the crankshaft seal flush 05:15 – Case dowels installation 05:30 – Using aluminum tube to seat dowels 05:35 – Mounting the shimmed crankshaft 05:50 – Cleaning gasket surfaces 06:15 – Handling snapped oil jet & resizing 06:45 – Mounting engine cases together 06:55 – Lubricating threads & torquing bolts 07:05 – Installing mainshaft seal 07:15 – Measuring axial play & reshim crankshaft 07:50 – Installing sensors & verifying crankshaft play 08:05 – Installing oil filter 08:20 – Torquing bolts to 10 Nm 08:30 – Installing spacer & O-ring between front sprocket and mainshaft 08:35 – Outro & reminder to subscribe