HS50 max safe revs?

[FirePowerMinis]

I'm replacing a tired HS40 with a fresh 50, using the aluminum flywheel, stock rod and cam.
Porting and .030 cut from head, manifold dent removed.
How tight can these be twisted before failing?

 

[Havasu Dave]

Exactly 4200 RPM. You can set the gov right at it. Use as straight and short of an exhaust as you can get away with. Tec's like it, especially if they're breathing pretty good.

Just kidding about Revs. It's really 4250. Seriously, the rod does not like it. There are after market rods and cams out there I thing. Cams for sure.

 

[FirePowerMinis]

Haaa, Thanks! I thought they were pretty limited, from my snowblower experiences, but good to get the experts advice.

I saw a thread where a modded OHV rod was used, but not sure it's worth the trouble.
Delta, Tim Isky, lots of places to get a regrind, but it's in a clean Roadster, wanna keep it stock-appearing and not too twitchy for parade duty.

Terry

 

[FirePowerMinis]

Man, they stretched the bore about as far as the valve seat block allows, eh?

 

[capguncowboy]

Man, they stretched the bore about as far as the valve seat block allows, eh?
View attachment 75538

Oh wow! That seems like it would cause problems for the engine block in the long run

 

[Havasu Dave]

Haaa, Thanks! I thought they were pretty limited, from my snowblower experiences, but good to get the experts advice.

I saw a thread where a modded OHV rod was used, but not sure it's worth the trouble.
Delta, Tim Isky, lots of places to get a regrind, but it's in a clean Roadster, wanna keep it stock-appearing and not too twitchy for parade duty.

Terry

I'm no expert, but I had some discussions with one. :laugh: Basically you adjust the governor by the book, but use the lower gov spring in the top gov arm hole. (the one for the spring, not the rod linkage) Then you set the throttle and arm length, and with a new spring should get 4400 revs.

Roadster drive system should keep torque loaded pretty good anyway, but to keep it original, I guess you'll suffer with that exhaust. No big. Did the same thing on a Powell with an HS40. Breathing real well, but a muffler, then a spark arrestor to choke it back down. Cool block you have there. I bet it ran a pretty penny.

 

[FirePowerMinis]

Haaa. I've seen your input on threads

Block was a recycling find, $.25/lb I think.
I cleaned up the holes a bit.
Port was a lot bigger than the 40 pipe and port, so I sleeved and smoothed it a bit.

 

[FirePowerMinis]

Rings were in the way, made it look closer. Still crowding it.
I rolled the edge a tad to smooth flow in to the hole.

 

[ole4]

You can use the ARC rod unmodified in them for a little insurance. Still have to worry about the flywheel but the stock rod was always the first to go if you ran them ungoverned. I have used this rod in a few HS50's one with many hours on it.

OldMiniBikes has them here
https://www.OldMiniBikes.com/Performance-Engine-Parts/Tecumseh-5_5-HP

 

[David wulf]

I have a HS 50 that will turn 6200 with no problem . It has a dyno 255 cam and a ARC billet rod in it like the one OLE posted a pic of . I'am running a stock carb slightly modded . It's the one on my Powell in my avitar .