'00 KTM 640 LC4 Adventure R fuel comparison

The loss in HP shows demonstrates that the engine is over the edge (ignition timing too advanced, still too much compression, still not enough exhaust flow etc.) and therefore at risk for detonation when using 89 octane. The delta points to it in fact still possibly being over the edge with 91. One way to test that would be to try more octane yet to see if HP increases. Nowadays we use the NOx content in the exhaust gas to give a feel for detonation risk (we didn't have that capability when this test was performed).

before & after modifications

piston & pin

detonation-induced mechanical failure
©motolab 2002-2019