Over reving onan
 

Guys, I’m stuck in need need help. About a year ago, I took my onan out of my 1914 To replace the starter. I put it all back together and it ran like a dream. However, about 30% of the time when I start it up the engine revs Like it’s Going to blow up. I can control it by pulling the throttle all the way to slow, but I only get about a quarter inch of movement on the throttle stick before it’s at wide open throttle. There are times where I can shut the engine off, Not touch the throttle , Wait a minute and start it back up and it’ll run perfectly fine again. I’ve taken the air cleaner off several times to try and Find some sort of a problem In the linkage but I just can’t find anything. I’ve never experienced anything like this before with an engine. Anybody have any ideas?

Since you say you pulled the engine, you must have disconnected the throttle cable. Therefore, I would look and make sure the outer throttle cable sheathing is properly attached. And check that the governor linkage hasn't been compromised.

The Onans have a flyball governor, and they have been known to loosen up over time and cause all kinds of erratic governor behavior. There is an updated spacer that prevents overspeeding if the spacer slips on the camshaft. This may be what is happening to yours.