Tecumseh Motor Swap?

I have a very dead 76 Sachs that was thrown in for free when I bought a complete bike. I thought it would be a good candidate for electric conversion but batteries are very pricey. Not much available in two stroke motors except for the bicycle 80 cc kits that are everywhere. Looked at a Rotax 125 go cart motor but it was 4K new. Then I remembered I had a dead Snapper 2 stroke snow thrower that I picked up for 25 bucks. The motor displaces 98 cc and is rated at three HP. Compression is good and I think with a little love and a pipe four horsepower is attainable. Could be a fun winter project. Good idea or crack pipe?...LOL

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Re: Tecumseh Motor Swap?

Cool. A down draft carb.

Re: Tecumseh Motor Swap?

I'd do it . Even though the motors are more a one speed .

Probably need a carb replacement . Do a port map out of curiosity and education .

Most likely have to build or cobble a pipe to fit the outlet .

Sounds like a fun project . Even if it does fail to be spectacular . ;)

Re: Tecumseh Motor Swap?

Not quite crack pipe, but I can't imagine how it would fit, kind of large for a moped frame, at least it's 2 stroke....what's wrong with the engine on the bike?

Re: Tecumseh Motor Swap?

https://www.mopedarmy.com/forums/read.php?7,3577349,3577349,flat=1#msg-3577349

Nothing new under the sun as they say...

This is a pretty brute force way to do it but if you wanted to do it a nicer way you could make plates to bolt into the motor mount and bushings for a pedal shaft, then run a motobecane pulley on the pedal shaft with a go kart centrifugal clutch.

That guy actually came out to a cranks ride one night, I wasn't there but the guys that were confirmed it was going damn near 50 with decent acceleration. Crazy. I got a couple of those engines laying around, always thought it might be fun.

Re: Tecumseh Motor Swap?

Ted Grant /

> Stephen Keller wrote:

> -------------------------------------------------------

> Not quite crack pipe, but I can't imagine how it would fit, kind of

> large for a moped frame, at least it's 2 stroke....what's wrong with the

> engine on the bike?

I'll make it fit even it is a little too low for comfort. The engine on the bike endured 30 years in a chicken coop and was locked up solid. It will need a new piston and jug to run again.

Re: Tecumseh Motor Swap?

Ted Grant /

@ Graham...Good idea on the Motobecane pulley. Unfortunately this motor has a 5/8 inch output shaft so my centrifugal clutch choices are limited. I hope to make up some custom brackets and maintain a good chain line. I can usually McGyver almost anything to work and I like to say "If I can't fix it it ain't broke".

Re: Tecumseh Motor Swap?

Probably Fred /

Somebody here on MA already did something like that and he made a thread.

He had a magnum with a 2 cycle snow blower engine on it that had a simple centrifugal clutch with chain. Search for the thread

Re: Tecumseh Motor Swap?

Re: Tecumseh Motor Swap?

> Probably Fred wrote:

> -------------------------------------------------------

> Somebody here on MA already did something like that and he made a

> thread.

>

> He had a magnum with a 2 cycle snow blower engine on it that had a

> simple centrifugal clutch with chain. Search for the thread

Graham linked that thread already

Re: Tecumseh Motor Swap?

Ted Grant /

> Luna Moto wrote:

> -------------------------------------------------------

> This would be a better option if you wanted to go full motor swap IMO

>

> https://www.ebay.com/itm/49CC-Air-Cooled-Engine-Carb-For-KTM-50-SX-50-SX-PRO-SENIOR-Dirt-Pit-Cross-Bike-/393544870798?mkcid=16&mkevt=1&_trksid=p2349624.m46890.l49286&mkrid=711-127632-2357-0

That's a decent looking motor compared to most of the bicycle conversion kits. Unfortunately I'm in Canada and the price could easily double with currency exchange, duty and Fed Ex's creative ways of charging up to 100 bucks for "handling". I hope to build this motor and have less than 500 into the whole bike...

Re: Tecumseh Motor Swap?

Aaaaand scratch that, there was another one of these rolling around southern Wisconsin I think the guy was in Janesville or something? I don't know... He had a thread on here too but I can't find it, anyhow it's a good idea.

Be advised 4500 is probably max safe rpm for these flywheels, most lawnmower flywheels explode quite violently around 6000

Re: Tecumseh Motor Swap?

> Graham Motzing wrote:

> -------------------------------------------------------

> Aaaaand scratch that, there was another one of these rolling around

> southern Wisconsin I think the guy was in Janesville or something? I

> don't know... He had a thread on here too but I can't find it, anyhow

> it's a good idea.

>

> Be advised 4500 is probably max safe rpm for these flywheels, most

> lawnmower flywheels explode quite violently around 6000

Maybe banding the flywheel would help ? ;)

Re: Tecumseh Motor Swap?

You can buy a shaft adapter sleeve to put a 3/4 clutch on a 5/8 shaft. Easy peasy. Hardest part is that sometimes the shaft on them is super long and only the end is machined for the pulley, you could put a clutch on a jack shaft or use a Moby clutch pulley too.

Re: Tecumseh Motor Swap?

> P D wrote:

> -------------------------------------------------------

> > Graham Motzing wrote:

>

> > -------------------------------------------------------

>

> > Aaaaand scratch that, there was another one of these rolling around

>

> > southern Wisconsin I think the guy was in Janesville or something? I

>

> > don't know... He had a thread on here too but I can't find it, anyhow

>

> > it's a good idea.

>

> >

>

> > Be advised 4500 is probably max safe rpm for these flywheels, most

>

> > lawnmower flywheels explode quite violently around 6000

>

> Maybe banding the flywheel would help ? ;)

I mean if you want to trust that? YouTube kart motor exploding flywheel... It's like a fuckin hand grenade when they go.

Re: Tecumseh Motor Swap?

Ted Grant /

Good advice...This motor has a cast aluminum flywheel with magnets pressed in place. There is a warning cast into the flywheel that alterations or misuse may create a burst hazard. I'll figure out a way to shield my leg since misuse is highly probable...

Re: Tecumseh Motor Swap?

Ted Grant /

Thanks for your replies everyone. I made some progress on the motor swap and have the motor hanging on the frame. I made a template with cardboard then transferred it to 5 mm plywood for proof of concept. The motor is just forward enough to clear the cast intake port on the motor. Chain line looks good and I have to make a bracket for the other side of the frame. I'll bridge the two brackets together with square tubing to add rigidity. Only obstacle is the pedal shaft has to be lengthened on the fan shroud side and a high offset pedal arm will be used. There are a couple of bolts on the top of the fan shroud that can be used with custom brackets to the side cover tabs. I'm thinking a cheap 19 mm pit bike carb can be used to get it running. A custom intake elbow will be a pita but I know of a shop that fixes aluminum boat propellers and fabricates stuff. Still have to source a 28 mm header pipe and aftermarket expansion chamber but It looks promising if I can find a good welder...

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Re: Tecumseh Motor Swap?

That looks much better than I had anticipated, great job!

Re: Tecumseh Motor Swap?

Oh dang, I didn't realize it's a 504. You could put the motobecane pulley right on that pedal shaft with a comet clutch or a fixed pulley with a Doppler clutch pulley.

Looks good on there, excited to see how this goes.

Re: Tecumseh Motor Swap?

Ted Grant /

Thanks Stephen...Doesn't look too janky for a Redneck build. Priority is to complete the motor mounts in 1/8th steel plate and get it running with the original muffler for now...

Graham... Might go with the Motobecane pulley and a idler for belt tension. The Doppler clutch assembly would be nice but too much money for this build...

Re: Tecumseh Motor Swap?

I got one of these 5hp motors sitting on a shelf. Watching this.

Re: Tecumseh Motor Swap?

Looks good. What ya gonna use for a new intake?

Re: Tecumseh Motor Swap?

Ted Grant /

> live ɘvil wrote:

> -------------------------------------------------------

> Looks good. What ya gonna use for a new intake?

Thanks...I just ordered this carb that comes with a elbow intake. At least one end will be correct and I'll fabricate a plate for the motor with a rubber coupler. Final design depends on what Home depot has in their plumbing department...

https://www.amazon.ca/dp/B08XYPH4TP/

Re: Tecumseh Motor Swap?

I like the wood trial-and-fit template approach too.

Re: Tecumseh Motor Swap?

I wasn't gonna say this because it's a terrible idea, but when we were kids, I 'turned down' a lawnmower crankshaft by holding a flat file to the running engine. Do with this knowledge what you must...

Re: Tecumseh Motor Swap?

> Graham Motzing wrote:

> -------------------------------------------------------

> I wasn't gonna say this because it's a terrible idea, but when we were

> kids, I 'turned down' a lawnmower crankshaft by holding a flat file to

> the running engine. Do with this knowledge what you must...

I did the same thing with a shaft for a mud motor I built. I had to taper the 3/4 shaft for the propeller to fit. Then I had to cut a keyway in it with a dremel. I have also done the same with a treadmill motor so I could put a different pulley so I could run the motor with speed control on my metal bandsaw

Re: Tecumseh Motor Swap?

You could always block off the old intake and put a reed and carb on the bottom crankcase cover.

Re: Tecumseh Motor Swap?

Ted Grant /

> Graham Motzing wrote:

> -------------------------------------------------------

> I wasn't gonna say this because it's a terrible idea, but when we were

> kids, I 'turned down' a lawnmower crankshaft by holding a flat file to

> the running engine. Do with this knowledge what you must...

I would totally try this. Just have to figure out motor rotation so you're cutting away and not into yourself...LOL.

Re: Tecumseh Motor Swap?

Ted Grant /

Some progress this week. I picked up 11 gauge steel plate and the motor is solidly attached. Got a deal on a rewrapped pit bike carb from Amazon warehouse. The inlet is 26 mm so I might have to make a restrictor plate. The supplied intake elbow doesn't help much so I'll be busy cobbling together a full custom intake. I'm considering a hardwood base plate or phenolic 1 inch thick sheet connected to EMT steel pipe. Will upload a video once I get it fired up...

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Re: Tecumseh Motor Swap?

Dang that looks skookum as frig

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