This may be a silly question but here goes... Can the reed valves in a 75 DT400 be installed upside down? If so would it cause an issue? The manual didn't really show much on the subject and both sides of the reeds look identical. I just replaced the intake manifold/rubber carb boot. Also what kind of fuel do you guys run in these old Enduros? Ethanol free is hard to come by where I'm at so I've been using 93 octane with yamalube 2 stroke/injector lube or Honda 2 stroke injector/premix oil. Any help is appreciated!

Your safe on the reeds , either way is good. Fuel is another topic , But on a stock low compression engine pump premium is fine , a good synthetic oil ( red line is my preference ) will prevent the problems ethanol if i premix form

Rich

Much appreciated! That's kind of what's fun about these old bikes. You gotta tinker around with them and tune them. Not like the newer bikes that just start and go with little or no maintenance.