Tecumseh HS40- What is the thread on the flywheel nut/end of crankshaft?

creia

creia

#1
#1
I have a 1970s HS40 crank that has bunged threads on the flywheel end. I cannot get the flywheel nut to even start threading on. I am hoping to get a die and clean them up. Does anybody know what thread this is? Thank you for any help.
Michael
 
minikenny

minikenny

Member
#2
#2
I think the small taper is 7/16-20 (NF)

The bigger taper is 1/2-20 (NF) I believe.

What size wrench goes on the nut?
 
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creia

creia

#3
#3
Thank you minikenny,
Wrench size is 11/16". This is the flywheel nut that has the small flange/shoulder that fits into a large, slightly convex washer.
Michael
 
creia

creia

#5
#5
Thank you minikenny- it is sincerely appreciated. I would assume that the crankshaft is hardened as would be the die. I wonder how effective the die will be?
Michael
 
Ajf

Ajf

#6
#6
Micheal, I would try a thread file first and try to restore the threads. They are square and come with 4 different thread pitches on each end for a total of 8. You'll want the side marked 20.
 
creia

creia

#7
#7
Ajf said:
Micheal, I would try a thread file first and try to restore the threads. They are square and come with 4 different thread pitches on each end for a total of 8. You'll want the side marked 20.
Click to expand...
Thank you Ajf- I will look into that!
Michael
 
1

1971_MB1A

Well-Known Member
#9
#9
If the threads at the end of the shaft are "mushroomed" over and or damaged remove the spark plug (so engine spins easily) and spin the engine over from the pto side using an electric motor with a belt and common "v" grove pulley (or use a bolt and socket with an extension and a drill if you have a drilled and tapped crankshaft) and hold a coarse cut metal file (or a die grinder with a flat disc) at an angle against the bad/mushroomed threads until it's tapered enough to run a die with tapping oil over it. Loctite nut just snug and it should be fine as I've done several of them that way that were damaged and never had a problem.
 
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