Engine rebuild (Tecumseh 5hp - "H50") with reverse sheave - proper placement of gear?

jpilk99 · Nov 12, 2020

Engine rebuild (Tecumseh 5hp - "H50") with reverse sheave - proper placement of gear?

I am trying to salvage an older Tecumseh H50 (Horizontal/5hp) engine after the piston's connecting rod let go and things got ...messy inside. This engine has 2 sheaves/pulleys, 1 that comes off the crank and the other (the reverse) that comes off the shaft with the cam lobes; (so I guess that's the cam shaft?).

Anyhow, after bringing the motor in and on the bench, I cleaned it off and then pulled off the front cover. The reverse, or cam shaft, came off with the cover while the crank (obviously) stayed in place. I did not see the exact orientation of the cam shaft to the crank - how & where their gears meshed - and now I'm in a jam as I don't know where to re-mesh the cam shaft gear back with the crank gear. Can someone tell me if there are "alignment" marks or anything? I've attached a picture, red arrow pointing to crank shaft and yellow pointing to cam shaft.

Thanks so much. New piston/rings/connecting rod etc. showing up this weekend. Honing cylinder today.

RandyT · Nov 12, 2020

Re: Engine rebuild (Tecumseh 5hp - "H50") with reverse sheave - proper placement of g

The dot/hole close between the two teeth on the camshaft will align with a dot on one of the teeth on the crankshaft gear.

jpilk99 · Nov 12, 2020

Re: Engine rebuild (Tecumseh 5hp - "H50") with reverse sheave - proper placement of g

RANDYT said:
The dot/hole close between the two teeth on the camshaft will align with a dot on one of the teeth on the crankshaft gear.

Thanks Randy, that is exactly what I would've thought - but I see no corresponding dot/hole/marking on the crankshaft gear. I thought maybe the cutout of the key-way...?? Here's 2 more pics with focus on the gear, keyway notch at top in 1 pic and bottom of other. There is no "dot" on any gears that I can see, however, the gear tooth in line with the keyway is at a 30-degree or so decline which differentiates it from the other gear teeth.

Other questions now coming to mind:

How do I know how/where to bolt on connecting rod to crank? I assume there's a mark somewhere I need to align too?
I want to take out valves to clean them and their seat/wholes, but, they don't want to just "pop" out, like their ...pushrods/tappets did when I took the cam shaft out.

Thank you!!!

Jay

jpilk99 · Nov 12, 2020

Re: Engine rebuild (Tecumseh 5hp - "H50") with reverse sheave - proper placement of g

jpilk99 said:
Thanks Randy, that is exactly what I would've thought - but I see no corresponding dot/hole/marking on the crankshaft gear. I thought maybe the cutout of the key-way...?? Here's 2 more pics with focus on the gear, keyway notch at top in 1 pic and bottom of other. There is no "dot" on any gears that I can see, however, the gear tooth in line with the keyway is at a 30-degree or so decline which differentiates it from the other gear teeth.

Other questions now coming to mind:

How do I know how/where to bolt on connecting rod to crank? I assume there's a mark somewhere I need to align too?
I want to take out valves to clean them and their seat/wholes, but, they don't want to just "pop" out, like their ...pushrods/tappets did when I took the cam shaft out.

Thank you!!!

Jay

Disregard valve question, will just use my polishing kit

mark02tj · Nov 12, 2020

Re: Engine rebuild (Tecumseh 5hp - "H50") with reverse sheave - proper placement of g

Notice the tooth by the keyway on the crank is slightly different than the rest of them. That's the alignment tooth. Line that tooth up with the one by the hole in the cam.

Is this motor out of a tiller? If I'm understanding your description correctly, there's a second pully/shaft that comes out the back? If so, I don't think you need to worry about aligning that one.

RandyT · Nov 12, 2020

Re: Engine rebuild (Tecumseh 5hp - "H50") with reverse sheave - proper placement of g

I would also agree that the different tooth that aligns with the keyway is the timing tooth.

jpilk99 · Nov 12, 2020

Re: Engine rebuild (Tecumseh 5hp - "H50") with reverse sheave - proper placement of g

RANDYT said:
I would also agree that the different tooth that aligns with the keyway is the timing tooth.

Thanks both. That's what i figured, since it's the only different one on the gear. Not for nothing, mark, and I could be wrong, but, I think lining up that second pulley/shaft IS very important because it has the cam lobes on it, hence the timing of the valves are dictated by it. Feeling good though, now, with you guys' help. Thank you.

denchen · Nov 13, 2020

Re: Engine rebuild (Tecumseh 5hp - "H50") with reverse sheave - proper placement of g

If you put the camshaft so that both valve cam followers are just touching it, `valves on the rock` one just closing, and the other about to open. Put the piston at top dead center, it should be about right.