HS50 - What flywheel do I need?

jackeo21

jackeo21

Active Member
#1
#1

A few months ago, I was quite involved with my HS50 restoration and making good progress. A rarity in my neck of the woods, I've had to bring in a couple of bits and pieces from the USA.

One key part that I imported, was a crankshaft. My original had a 1" PTO, and a stripped thread on the flywheel side.

I imported a really nice HSSK50 crankshaft, 3/4" PTO, just what I was after. I didn't realise that the flywheel taper would be slightly different, though. The part number for this crankshaft is #37245.

The problem I now face is that I need the correct flywheel to continue. Which flywheel am I looking for? My engine had the late 70s (presumably) aluminium flywheel, which I noticed was heavier than the earlier aluminium flywheels I have handy. None of which suit the taper of my new crankshaft.

Any guidance on flywheel part numbers etc would be really helpful. I'll take any measurements needed to make that happen. I look forward to giving this Tec' a new lease on life!

Pictured below is the "mess" - as purchased. The original color appears to be white.
IMG_5943.jpeg

This is the flywheel that it had paired with its original crankshaft. The taper on this is different to the one on the crankshaft I'm trying to use.
IMG_5944.jpeg

Not the best picture, but this is the replacement crank I'm using.
Screenshot 2026-08-26 at 10.44.26 PM.png

Thanks!
 
Havasu Dave

Havasu Dave

Moderator
#7
#7

fasttony said:
Dave

My question could have had a little more info, the threaded insert would be used to repair the original crank not the different replacement.
Click to expand...
Sure, I meant no disrespect, I just wasn't in a writing mood. :) You have a heavy weight spinning at the end of that shaft. Right away, you have to have it as strong as it was when it was forged. Almost impossible. Not possible with threaded bits holding the end together.

Second, the level of accuracy required to accomplish this is at a high skill level. It has to be perfect in order to not vibrate- which would result in catastrophic failure. Any wobble is also going to affect the timing coil gap, but it will explode all over your leg long before that becomes an issue.

Since we're only talking about thread and not taper, a possible repair or modification to threaded section could come from rethreading the end, then threading on a threaded sleeve, or welding on a threaded sleeve and rethreading it. I don't mention a spacer within the bore, since reducing the diameter of the threaded area would reduce the ability of the nut and belleville washer to hold it on the shaft.

This is merely my opinion based on how I would do something. I tend to want to do things so they are solid, and 100%. I am sure the "git-er-done" crowd could employ something with drilling, threading and loc-tite and have the engine start but it would not be something I handed to a loved one, or entrusted my bits too.
 
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