1972 Norton Commando Combat - Dynamic Wet Sumping 

In this video, Paul, John & I will try to determine the root cause of the problem that Paul encountered during the recent Boring Cornfield Concourse group ride. Paul describes what is known as "dynamic wet-sumping”, where the engine crank case is filled with engine oil - BUT while the bike is running! This is apparently a known and documented issue. Dynamic wet-sumping on a 1972 Norton Commando Combat is a very specific oiling issue that appeared most often on those early high-compression “Combat” engines. Nature of the Problem Normally, “wet-sumping” means that oil drains via gravity from the oil tank into the crankcase while the bike sits unused. Dynamic wet sumping is different: it happens while the engine is running! Instead of the timed breather and scavenge pump keeping the crankcase clear, oil builds up in the sump during operation. This causes excessive crankcase pressure, smoky exhaust, oil blowing out of the breather, and a loss of oil supply to the top end because it’s stuck in the crankcase rather than circulating properly. Root Causes (Combat-specific factors) 1. Breather relocation Earlier Commandos had the timed breather on the end of the camshaft. For 1972 Combat engines, Norton moved the breather to the back of the crankcase, behind the camshaft. In practice, this location proved ineffective at scavenging oil mist and crankcase pressure at higher RPMs. Paul has already moved the breather, so this has been eliminated as the root cause 2. High RPM / compression stresses The Combat spec (10:1 compression, hotter cam, higher revving) produced more blow-by and crankcase pressure than the redesigned breather system could handle. Again, Paul has fitted a new modified breather in a more optimum location, so this has also been eliminated as the root cause 3. Scavenge pump limitations The gear-type oil pump sometimes had excessive internal leakage or insufficient capacity meaning oil delivery to the tank could not keep up with what drained into the crankcase. This is our hypothesis  going into this evaluation, especially following a recent seizure, when metal particles may have entered into the oil pump Paul will keep a close eye on the oil levels as he test rides his bike after this effort _____________________________________________________________ 📖 TIMESTAMPS 00:00 Intro _____________________________________________________________ 🔗 LINKS See Paul's Land Speed Record! Paul's moving LSR video from September 2016:    • Sir Eddy's Rocket 2016 Record Runs Bonnevi...   Taper tool https://www.thebonnevilleshop.com/pro... Slide hammer: https://www.thebonnevilleshop.com/pro... _____________________________________________________________ SUPPORT 🔴 Please SUBSCRIBE to The Mighty Garage https://www.youtube.com/c/themightyga... ☕ Would you like to buy me a coffee? 😉 If you enjoy my videos and would like to support my channel, please consider donating here: https://buymeacoffee.com/themightygarage A huge thank YOU in advance 🙏 _____________________________________________________________ 📧 CONTACT [email protected] _____________________________________________________________ 🏷️ HASHTAGS #themightygarage _____________________________________________________________ SOCIALS   / themightygarage