I´m a noob, so this might be a stupid question but my ´78b CB400Tii Hawk keeps stalling out when I clutch to downshift -- tach is busted so I can´t say the rpms. If I get it into the next gear down quickly, the engine pics right back up and sounds great, but if i hold the clutch in for too long -- even down from 2nd into a stop sign -- the engine just conks out and i have to start it up again. It idles fine. When I shift into neutral all´s good, but when I´m holding in the clutch and the bike is moving the engine sounds ready to turn off and it usually does. Thoughts?