HSSK40 vs. HSSK50

#1
I have both an HSSK40 and a HSSK50 both are about the same vintage.

I assumed the 50 was a more powerful engine but today a small engine mechanic told me they are both the same engine with the only difference being the advertised HP.

Is that true?
 

delray

Well-Known Member
#2
bore sizes are still different and the counterweight on the cranks. if your building a hot rod the 50 would be better. if you're keeping it stock? you may not feel a difference in power....:scooter: I'm sure someone else will Chim in with more info thumb1.PNG
 

cfh

Well-Known Member
#3
a stock HS50 (or HSSK50) is definitely more powerful than a HS40 (or HSSK40). And frankly, due to emissions, at some point the HSSK40 actually decreased in CCs (so it's more like an H35), but Tecumseh still calls it a "4 hp" engine.

The amount of work to rebuild a HS40 is exactly the same as a HS50. So why use an HS40? .... well unless you have a pre-1973 HS40 with a rounded blower housing (like say on a Rupp), and you want to maintain that "look." And HSSK50 rings sets are generally easier to get than any HS40/HSSK40 ring set.

And let's be frank here... we're all old. And probably fat. well certainly fatter than the 12 year old version of ourselves. so don't you want a little more power that an HS50 would offer? of course you do...
 
#4
a stock HS50 (or HSSK50) is definitely more powerful than a HS40 (or HSSK40). And frankly, due to emissions, at some point the HSSK40 actually decreased in CCs (so it's more like an H35), but Tecumseh still calls it a "4 hp" engine.

And let's be frank here... we're all old. And probably fat. well certainly fatter than the 12 year old version of ourselves. so don't you want a little more power that an HS50 would offer? of course you do...
I was just reading the specs on the two engines on the pinrepair you so generally provided. Obviously with the bigger bore, the 5 HP is the way to go. I don't know what that guy was telling me....
 

cfh

Well-Known Member
#5
I think what happened was the HS40 and HSSK40 was discontinued about 1998 and the H40 came about. This 1998 and later H40 is actually the H35 sized piston. So I guess an HS40 or HSSK40 is still 172 cc, opposed to 158cc. But regardless, i would still stick with an HS50 or HSS50 (198cc.) The increase in power is very noticeable, even in stock format, over an HS40/HSSK40.
 
#7
I have a couple of Hs50s and i like them a lot. If you build them correctly they can make great power and be pretty reliable.
It's still a small frame so it can fit on a lot of bikes
 

delray

Well-Known Member
#8
I have both an HSSK40 and a HSSK50 both are about the same vintage.

I assumed the 50 was a more powerful engine but today a small engine mechanic told me they are both the same engine with the only difference being the advertised HP.

Is that true?
nice thing about the HSSK50. still easy to find rings...lol
 
#9
I have two Rupp RR2's and have HS40, HS50 and HSSK50's (with larger HS40/50 exhaust valves) I did not find any difference in driving performance between them. I swapped the engines, carburetors and different tuning settings more than once trying to get the fastest one on my bike, the only noticeable difference was running them with the oil level near the low mark on the stick.
 

cfh

Well-Known Member
#10
I can tell the difference, to me it's quite a difference. Of course i'm riding off road, not on the street. the additional HP is quite noticeable to me on the hills and out of the corners.
 

DaddyJohn

Well-Known Member
#11
I’m not sure what the debate is, you’re just going to need to build up two mini bike chassis, and put the HSSK50 on the one you want to accelerate with a bit more authority. :)
 
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