Freshly rebuild stock 1972 XS2 motor with Mikuni VM34 carbs and BB ignition. Header pipes from Mikesxs with a 1 3/8" I.D.
With the commando style mufflers mounted the engine bogs down and looses all power at around 3-4k rpm. I can see a cloud of fuel/exhaust vapor standing in the carb inlet when revving in neutral so suspect the problem is exhaust reversion. Tried running with open mufflers and then the bike pulls much stronger over the enire rev range so confident it's an exhaust problem.
Feels like it's running rich, but I've tried smaller main jets (all the way from 190 to 120), but that doesnt solve the problem, only masks it slightly. Still has really poor mid range power.
Anyone else experienced reversion problems with Mikesxs commando exhaust system? Should I try torque inserts? I know the stock header pipes are smaller (1.25" I.D?) and that the XS1/XS2 has a slightly hotter cam than the the later model so maybe that contributes?
With the commando style mufflers mounted the engine bogs down and looses all power at around 3-4k rpm. I can see a cloud of fuel/exhaust vapor standing in the carb inlet when revving in neutral so suspect the problem is exhaust reversion. Tried running with open mufflers and then the bike pulls much stronger over the enire rev range so confident it's an exhaust problem.
Feels like it's running rich, but I've tried smaller main jets (all the way from 190 to 120), but that doesnt solve the problem, only masks it slightly. Still has really poor mid range power.
Anyone else experienced reversion problems with Mikesxs commando exhaust system? Should I try torque inserts? I know the stock header pipes are smaller (1.25" I.D?) and that the XS1/XS2 has a slightly hotter cam than the the later model so maybe that contributes?