I recently got a clean, low hours HS50 67061A (1975 I believe). Can the original 1" crankshaft be replaced with a 3/4" crank? I've seen a thread that discussed machining the 1" crankshaft down, but if replacement is possible with no resulting engine damage, that would be my preference. I may look in to a 1", 12 tooth clutch for #35 chain if this would work too. Not many choices there. Any advice would be appreciated to this newcomer. Thank you!
Can HS50 1" crankshaft be replaced w/ 3/4"?
- Thread starter Rhodyjoe
- Start date
- Tags 3/4 crankshaft hs50 replaced
So far I have found the following: TEC crankshaft part number 34740 is a 3/4" dia. crankshaft spec'd for the HS50 engine.
My concerns are whether the age of the my motor ('75) is compatible, or if later HS50 engines used an updated version crank.
Also, should the cam be replaced if changing from 1" to 3/4" crank? And yes, I will find an ace Tecumseh mechanic to do the work. :thumbsup:
Thanks, - Joe
My concerns are whether the age of the my motor ('75) is compatible, or if later HS50 engines used an updated version crank.
Also, should the cam be replaced if changing from 1" to 3/4" crank? And yes, I will find an ace Tecumseh mechanic to do the work. :thumbsup:
Thanks, - Joe
you want to stay away from that crankshaft (34740) They revised at the end of 1980 to a larger flywheel taper at that point which is what that is. You technically can use it, but you would also need matching flywheel, cup, belleville washer, nut..... If you happened across a "parts engine" that was 1980-1984 that would be fine because you have all the parts to swap then, you need to stay in the 1972-1979 range on yours. HS50 snowblower engines are usually around pretty reasonable, They usually show lighter wear internally due to the conditions they run in.
The cam has to come out to access the crank, but does not need to be replaced unless worn/damaged
Good luck with it :thumbsup:
The cam has to come out to access the crank, but does not need to be replaced unless worn/damaged
Good luck with it :thumbsup:
I appreciate the detailed explanation about the crankshaft revisions marcus. Based on the serial number of my HS50: 5099B, shown in the second photo, my understanding is this engine was built on 4/10/1975. I will look for a TEC 34740 crankshaft. And Sixpac440... I will keep the lathe option open. Thanks again! - Joe
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While your on the subject, I have a new short block with a 1" crank. i was thinking about changing out for a 3/4" or turning...
If I went with smaller crank would I need smaller bearing & seal for the cover? I'm thinking so. I'm in the process of reading all the HS50 mod. threads as I am a green horn with engines. I have three HS50 with points. The short block would be the one to build I think, with a hot coil...
It has the studs for it
If I went with smaller crank would I need smaller bearing & seal for the cover? I'm thinking so. I'm in the process of reading all the HS50 mod. threads as I am a green horn with engines. I have three HS50 with points. The short block would be the one to build I think, with a hot coil...
It has the studs for it
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Yes you are correct, it is a 1975 engine. But I think you are reading the info I posted up incorrectly.... DO NOT GET a 34740 crankshaft. Your flywheel parts WILL NOT fit that crankshaft. The 33677/33677a numbers I supplied earlier in the thread are the standard length 3/4" output bushing crank that your engine would use.
These are examples of the difference between the 1972-1980 (left) and 1980-1985 (right) tapers.
Biff, you would only need to change the cover IF you had them machine the crank down to Ball bearing sidecover specs. Bushing supported cranks were rougly 1" bushing, no matter the output size/style, Ball bearing cranks were rougly 3/4" at the bearing so the output end on them can only ever be 3/4" or smaller diameter. The 3/4 output bushing engines are just like owend said he had his cut down from the factory. Makes sense I hope???
Not the best shots, but all I have posted up in the photo section for reference These are bushing cranks from HS series engines:
Here is how the ball bearing supported shafts are cut:
These are examples of the difference between the 1972-1980 (left) and 1980-1985 (right) tapers.
Biff, you would only need to change the cover IF you had them machine the crank down to Ball bearing sidecover specs. Bushing supported cranks were rougly 1" bushing, no matter the output size/style, Ball bearing cranks were rougly 3/4" at the bearing so the output end on them can only ever be 3/4" or smaller diameter. The 3/4 output bushing engines are just like owend said he had his cut down from the factory. Makes sense I hope???
Not the best shots, but all I have posted up in the photo section for reference These are bushing cranks from HS series engines:
Here is how the ball bearing supported shafts are cut:
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