HS50 shearing key

copyman

Well-Known Member
#22
Ok, now it makes sense. The torque wrench I have goes to 250 in lbs. I was "assuming" all torque wrenches were in lbs since the L head manual has that as first on the spec list and my torque only has in lbs & nm. Now that I know it's ft lbs I'll go back to HF and pick up that cheap wrench.

Thanks again
 
#24
After rebuilding 20+ engines I must be really lucky to never have a key shear. I do everything by the book except the flywheel nut which I've always tightened by hand.
Just so this makes sense to me, if not torqued to spec what would cause the key to shear, being to loose? Each time I had to pull flywheel to replace the broken key had to use the flywheel tool because FW was on tight? I remove nut with impact wrench but always tighten by hand.
Thanks again for the help
I am not saying that is definitely what caused your flywheel key to shear in this instance- but it MIGHT have been. Regardless, you still need to get yourself the proper torque wrench and be using it when you are installing flywheels.
Michael
 
#25
Nahhhh- no need to spend that amount of money for that thing. The basic HF 3/8" drive that I mentioned (and personally use) they sell for
$ 20.00 will serve just fine.
Michael
Good ! Thank you tells me I'm good w/the little 100 Ft/lb 3/8" drive Craftsman clicker I've had for many moons now.
 

f4radar

Well-Known Member
#26
I think you will find it surprising how tough it is to pull that 37.5 lbs while you're trying to keep a grip on the fly wheel with a strap wrench that wants to slip and you with only two hands.
 
#27
Ok, so went to Harbor freight and the $20 torque wrench was rated 50-80 in. lbs, one for a few dollars more went to 100 in lbs. Looked at everyone available and none went to 450 in lbs which is what the spec is for FW nut. Highest rated was 200 in lbs. The one I have goes to 250 in lbs. which I bought on amazon for $50. I use it for every bolt on the engines except the FW. Now that I think about it when I was shopping for a torque wrench for first engine I rebuilt I couldn't find one that went that high or was very high price and why I always just tightened with a 1/2 ratchet.
Since this is first engine I didn't time and shearing the keys going to try timing and tighten with ratchet as I always do and see what happens. Worse that can happen is it shears another key.

Like I posted since it looked like the stater bolts were never touched I didn't time this engine. I "assumed" the timing was correct. But think it was Markus on this forum that posted "never assume anything with small engines"
Will report back
You are incorrect. The 3/8" drive HF for $ 20.00 is rated 5-80 FOOT LBS (not inch lbs) and that is the one you need. Like previously stated do the math and convert your 450 Inch lbs spec to foot lbs., which is 37.5
Michael
 
#28
I think you will find it surprising how tough it is to pull that 37.5 lbs while you're trying to keep a grip on the fly wheel with a strap wrench that wants to slip and you with only two hands.
There is a MUCH better (and easier) way than using a strap wrench to keep the engine from rotating while torquing the flywheel nut. Have you ever heard of the "rope trick"?
Michael
 

f4radar

Well-Known Member
#29
There is a MUCH better (and easier) way than using a strap wrench to keep the engine from rotating while torquing the flywheel nut. Have you ever heard of the "rope trick"?
Michael
No... so i googled it and a some xxx rated sites came up. Now I'm really curious.
 
#30
I think you will find it surprising how tough it is to pull that 37.5 lbs while you're trying to keep a grip on the fly wheel with a strap wrench that wants to slip and you with only two hands.
I brace the handle so it’s flat on the bench and the bench is holding it…if that makes sense….I think it was designed that way? Not sure….
 
#31
There is a MUCH better (and easier) way than using a strap wrench to keep the engine from rotating while torquing the flywheel nut. Have you ever heard of the "rope trick"?
Michael
No... so i googled it and a some xxx rated sites came up. Now I'm really curious.
Yank the spark plug and stuff a piece of old starter rope on the hole. A few inches should do it. Then turn the motor until the rope compresses and stops the motor. Torque away. To remove the rope, just turn the flywheel in the other direction.
 
#32
Yank the spark plug and stuff a piece of old starter rope on the hole. A few inches should do it. Then turn the motor until the rope compresses and stops the motor. Torque away. To remove the rope, just turn the flywheel in the other direction.
Mark G nailed it! Hell of a lot better way than struggling with a flywheel strap wrench. I first learned about it on this forum many years age from OldMiniBikes member "Metalman' who posted a good tutorial with photos. Any of you long-timers on here remember "Robert" (Metalman)? I wonder whatever happened to him- his posts were always very educational.
Michael
 
#34
Take a inner sheave from a torque converter, or probably the outer case of a centrifugal clutch or anything round that is 3/4" in diameter with a key way in it and drill two holes in it that line up with the holes into which you would bolt the torque converter mounting plate on the PTO side of the engine.
Bolt it snug and it works great for breaking the flywheel nut loose as well as for torqueing it down when installing. I was quite surprised nobody mentioned this. It is a very positive and safe way to lock the motor up. Saw this on a video some time ago, thought everyone knew about it.
 

markus

Well-Known Member
#36
Take a inner sheave from a torque converter, or probably the outer case of a centrifugal clutch or anything round that is 3/4" in diameter with a key way in it and drill two holes in it that line up with the holes into which you would bolt the torque converter mounting plate on the PTO side of the engine.
Bolt it snug and it works great for breaking the flywheel nut loose as well as for torqueing it down when installing. I was quite surprised nobody mentioned this. It is a very positive and safe way to lock the motor up. Saw this on a video some time ago, thought everyone knew about it.
I never bothered with anything like that becuase I would need 2 maybe even three for each size PTO, Then it rules out servicing say a vertical engine, genorator, small outboard, etc.. or lets say you just wanna pull the flywheel on an assembled bike, you know the ones you always see that "just need points, and a carb adjustment" listed for sale. Then there are the older Tecumseh/lauson engines I have rebuilt where they don't have threaded holes in the sidecover, Then I would need something else for a lot of the old Briggs and Scrapheaps etc.. etc... Plus I bought like 7 OEM Tecumseh strapwrenches out of old stock one time for like 12 bucks a piece :D

Just this month 2 of the engines that were assembled (and painted yesterday) The 1969 Rupp engine on the left is 5/8 and the 1968 on the right is 3/4" output, so that woud have ben 2 tools and take 3 times as long to set it all up, the wrench is just sitting right there already looped and ready to go...........If I ever lose a hand or arm My opinion may change though ;) IMG_3019.JPG
 
#37
Rebuilt this HS50 and it starts & runs good for around 5 minutes then shuts off while adjusting carb. When I try to restart it won't start after many pulls, check for spark, no spark. Take flywheel off and key is sheared in half. This has happened 3 times now with new genuine TEC keys. Not sure if shuts off because I'm trying to adj carb or the key shears while running? Also not sure if shearing of key is from many pulls trying to start after it shuts off.

Any ideas what it could be?

Thanks for the help.
My grass hopper hs50 does the same thing. I bought a 10 pack.
 

copyman

Well-Known Member
#38
Update: Timed the engine & tightened the FW as tight as I could without torque wrench and it's running great and not breaking the key.

Picked up the torque wrench from harbor freight and will use to tighten FW moving forward.

As for removing the FW I use an impact wrench. Nut comes right off without FW moving, put the FW nut back on flush with end of crank, tap a few time with hammer and large screwdriver behind FW and 99% of time pops right off. Even on badly rusted engines. The other 1% of the time I use a puller. I don't use impact wrench to put FW on! Use to only tighten by hand without torque wrench but after advice from this thread with use torque wrench.

Thanks again for all the replies.
 
#39
Update: Timed the engine & tightened the FW as tight as I could without torque wrench and it's running great and not breaking the key.

Picked up the torque wrench from harbor freight and will use to tighten FW moving forward.

As for removing the FW I use an impact wrench. Nut comes right off without FW moving, put the FW nut back on flush with end of crank, tap a few time with hammer and large screwdriver behind FW and 99% of time pops right off. Even on badly rusted engines. The other 1% of the time I use a puller. I don't use impact wrench to put FW on! Use to only tighten by hand without torque wrench but after advice from this thread with use torque wrench.

Thanks again for all the replies.
Good job. One more note if i might, key shearing is alot less likely when the p.t.o. is loaded, meaning wearing a clutch, pulley/belt,etc.
 
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