[rferguson]

It seems like it mostly happens in first gear since the lever is straight up, but when blowing, the vibration knocks it out of first slot into 2nd. Any ideas for tightening this? I looked up the lever spring part number but it's been discontinued. I have an older craftsman and the spring steel on that unit is much tighter than on the noma which is maybe 10 years newer.

Part "800" in the diagram is:
762333 LEVER, SPRING

 

[HushHouse254]

You may want to look at the friction wheel adjustment. If it is not within spec, it could cause it to jump out of the set gear.

 

[EntropyKnower]

I have the same shift arrangement on my MTD, and mine had the same problem when I bought it used. You just have to bend the lever spring a little so that it presses the shift lever into the notches of the shift-lever keeper with a little more tension. Easiest way is probably to unbolt the keeper from the "lower handle" and pull the shift lever rearward so that you bend the lever spring a little. That way when you bolt the keeper back on to the lower handle, the lever will stay snug against the notches. Like you say, the part is discontinued, so be gentle or you may be in trouble.

 

[rferguson]

That's exactly what I ended up doing and it seems to be working. At the same time however, the gear indicator plate came off loose being held in just by 2 self tapping screws. I couldn't get them to go back on tight since they were stripped so I ended up drilling out the bars and putting in nuts and bolts. It's steady as a rock now!

 

[EntropyKnower]

When I fixed mine, I unbolted the lever spring from the shaft (812) and then bent the lever spring in a vise. My lever spring is a little different from yours in that it is stamped so as to have a saddle shape that wraps most of the way around the shaft. I recall having a little trouble getting it back together. Later I noticed I could have done it the way I described above, the way you did it.