Using A 125CC Engine With Semi Automatic With Another Engine?

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Hello everyone, I had a question about a Gokart project I am starting. I currently have a Tecumseh HS40 in my possession that I’d like to put on a kart. It isn’t a requirement but I would like to have it be shiftable. I have heard around that you can take a seized 125cc clone engine and modify it to another engine. I don’t think the transmission is removable so I would have to work with the rest of the engine. Would this setup work? And how should I / would you go about it! Thank you all for all responses!
 
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Anything is "possible". If you have a Tecumseh in hand, and are asking about converting another engine (I assume you are talking about a GY6 type engine) into a transmission for your Tecumseh, I am afraid you have lost your marbles and will need to seek medical attention immediately.
 
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ezcome-ezgo said:
Anything is "possible". If you have a Tecumseh in hand, and are asking about converting another engine (I assume you are talking about a GY6 type engine) into a transmission for your Tecumseh, I am afraid you have lost your marbles and will need to seek medical attention immediately.
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I believe you are correct. Glad to see you believe in the power of the great Tecumseh however.
 
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It's not all that difficult to do especially if the engine with transmission is complete. The hard part is making it ALL fit on the cart.

The sorta short and simple of making it work varies slightly on the engine (for transmission) in question, but you really only need the top end off, swap the crank assembly for a solid straight shaft to be the "jackshaft" input, make a cover for where the cylinder bolted down to keep oil in the now transmission case. A couple lock collars (preferably steel so they can be welded in place solid once the jackshaft offset requirements have been determined.

This set up however will NOT work for engines that have a submerged ignition system (common on old Honda bikes 1967-1980 SL/CL/CB and likely many more) because you want to put your input sprocket where the flywheel used to be after carefully cutting away any obstructing case from the flywheel housing area.

Oh and yes, as. matter of fact I HAVE done it before with an engine... not from a seized engine but there isn't much difference between seized solid and having a valve hammered out behind the carburetor and a broken off conrod, it was als a 4 speed fully manual.

You could even put the original outer side cover back on the transmission once clearance accordingly.
 
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Denny said:
I’ve never heard of anything with a submerged ignition system. They were sealed up to keep them clean and dry though.
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1970 Honda SL175 K0
Wet clutch, oil cooled ignition, points driven by cam. MANY other Honda bikes were set up exactly the same especially the CB and CL sister bikes
 

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RLS_Underground said:
It's not all that difficult to do especially if the engine with transmission is complete. The hard part is making it ALL fit on the cart.

The sorta short and simple of making it work varies slightly on the engine (for transmission) in question, but you really only need the top end off, swap the crank assembly for a solid straight shaft to be the "jackshaft" input, make a cover for where the cylinder bolted down to keep oil in the now transmission case. A couple lock collars (preferably steel so they can be welded in place solid once the jackshaft offset requirements have been determined.

This set up however will NOT work for engines that have a submerged ignition system (common on old Honda bikes 1967-1980 SL/CL/CB and likely many more) because you want to put your input sprocket where the flywheel used to be after carefully cutting away any obstructing case from the flywheel housing area.

Oh and yes, as. matter of fact I HAVE done it before with an engine... not from a seized engine but there isn't much difference between seized solid and having a valve hammered out behind the carburetor and a broken off conrod, it was als a 4 speed fully manual.

You could even put the original outer side cover back on the transmission once clearance accordingly.
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That must have been a hoot!
 
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Denny said:
I had one of those when I was a kid. I wish I had it back! No oil in flywheel, points or coils.
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Oh no not the points or coils lol, just the stator and flywheel.

If you're not remembering the flywheel being submerged in oil you either never had the left engine cover off, or have simply forgotten.

The cam end was sealed off from the valvetrain (OHC) and had another lobe for the points contact breaker.
 
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Mine had a plate that sealed the cam on the shaft. The points were dry. Trying to remember from 40 years ago. It dropped a valve and wrecked a head on me 2x. That was the worst Honda I ever had. New heads from Honda with springs and valves was $107.00. Cam $24 and rocker arms, timing chain and gears gaskets were another $50.00.
 
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Denny said:
Mine had a plate that sealed the cam on the shaft. The points were dry. Trying to remember from 40 years ago. It dropped a valve and wrecked a head on me 2x. That was the worst Honda I ever had. New heads from Honda with springs and valves was $107.00. Cam $24 and rocker arms, timing chain and gears gaskets were another $50.00.
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Mine shockingly moved under it's own power with 0psi and 80psi compression when I got it and required a running second gear jump and bump to be started because the kicker was missing and the pinion shaft was chewed beyond putting a kicker on it.

It took a bit of work including electrical repair to replace the dead selenium rectifier with a modern solid state chip and other stuff.

It was a good little runner with the cleanest steel gas tank I've ever seen a bike of its type since most it's age up North are always found as rust cheddar. I used a piece of wood mop handle to push out 2 small dents on one side
 

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Denny said:
How cool is that! That’s a clean bike. Worth putting a new kicker and shaft into.
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I put too much into to sell it like I did, had I known that 5 years would bring me to a place where nobody gives a rodents rectum what you do as long as it isn't making problems or danger, I'd still have it for sure.

I legitimatized getting rid of it for $800 under the guise of having nowhere to enjoy it without being harassed or ticketed. Sadly I know full well it was worth double that because like I said, YOU DO NOT GET A 1970 ANYTHING with a factory steel tank that clean. Not even factory paint and emblems are ever as prestine as what that thing had
 
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