KLF300 alternator keyway

[cavry]

I have replaced the Alternator keystock 3 times in several weeks. the engine cranks instantly, idles well and runs smoothly for 30or 40 starts. Then suddenly when I go start it again, it won't start  Each time the key has been sheared.  The replacement fits the shaft and alternator firmly and I have not noticed any backfires.  Ideas? Suggestions?

Cavry

[Frank Angerano]

Have you checked the timing ? You may be getting a kick back and not a back fire.  Still odd that it’s breaking the key way but that’s where I would look first.  

[davefrombc]

Are you sure the nut Holding it to the shaft is tight enough?.  The  key shouldn't shear if all  is tight  so there is no pressure on it.  If  loose it  can work on the  key and eventually shear it. It would take a pretty  hard kick back to  make it shear a key on a tight assembly,  and it wouldn't run  on q  new key  unless timing was reset  if timing  slipped .

 

[cavry]

I was thinking along those lines. The roller bearing is fine.  I used a rubber mallet to seat the alternator before reassembling and then used a cross bar in the pull starter disc and torqued the end bolt to 60 ft/lbs this time.  Thankfully, timing hasn't slipped during any of the events.  Hoping this solves the problem.

Thanks for your input.

Cavry

[cavry]

I over torqued the end bolt by a few lbs but that seems to have solved the problem.  NO problems lately.

Thanks for the input.