Restoring a Tecumseh - another way

cfh

Well-Known Member
#1
I bought my first minibike in 1971, and it had a Tecumseh motor. So i grew up with these and learned a lot about them "back in the day". Fast forward a zillion years to today, and i've been collecting vintage bikes. And one thing is clear... most don't have their original motors (at least the ones i've been coming across). Heck most don't have *any* motor. And i'm not a Predator guy, i just don't like those, especially installed in a 1970s mini bike.

So with this in mind, i've been collecting Tecumseh 4hp and 5hp engines. Figuring i can't have enough of them, as i'll eventually need them for some random mini bike i come across. So far that theory has proved itself to be pretty true.

Now are you going to find 1969-1972 mini bike designed 4 and 5hp motors out there? Heck no. At least not for a decent price. If you're a "numbers matching" type guy, you should probably stop here and go to ebay... Because we're not getting that anal here. We just want a decent 4/5hp Tecumseh motor with the correct "look", and at a decent price.

So where do you get old Tecumseh flat heads? Well around here (Michigan), snow blowers are the donors. Winters in lower Michigan are pretty tame, but can be snowy, so snow blowers are A) common, and B) lightly used. Perfect donors. But with this in mind, you have to find the right motors (the right snow blowers.) Again I'm looking only for 4hp and 5hp Tecumseh motors. Tecumseh 3.5hp and lower won't work (they won't move my fat ass). Larger than 5hp won't work either (because of the lack of a HS motor size).

Edgers and leaf blowers are not ideal donors. Snowblowers are the best. why? the motors are just cleaner. No or little dirt to deal with (because they get used only during snow!) No air cleaners on snow blowers, because, well, why would you need one during the winter snow? It's pretty perfect for our purposes, with some modifications.

To get a Tecumseh 4 or 5hp, need to look for a snowblower in the 20" to 24" range. Wider than that and you'll be in the 6hp or larger range. Also personally i like old Craftsmen and Ariens models from the 1970s and 1980s. If they have points/condensor that's awesome, though not necessary. Pretty much any flat head until they get the "cyclone" style pull start (want the traditional 4 leg pull start, if possible.) Mind you the "cyclone" starter models are still good motors - they made these well into the 2000s. But the "look" isn't quite vintage (though the motors themselves are fine). We can 'fix' that look with older style decals later. So don't completely disregard these models, if one comes up for sale at a nice price.

Speaking of price, how much do these sell for? Well in the summer, snowblowers tend to be cheap. And older ones (not running) even cheaper. I've bought them from $10 to $75. Remove the motor, put the rest at the curb, and the metal scrapers get it and make it disappear!

Note you need to look at the PTO shaft on the motor. 3/4" is obviously the mini bike standard and what you want. A tapered PTO is the least desirable. 1" is also seen (and is OK.) but 3/4" is ideal. Don't worry if it's drilled or not. If it's a good motor and it's not 3/4" PTO, that's still OK, just a bit more work.

And i should mention that some snow blowers have a second small PTO (used for reverse often). No worries! Don't let a perfectly good motor pass if it has that. We can deal with it...

The one disadvantage to snow blower motors is the flywheels. It's steel and it's heavy. This is unlike "made for minibike" Tecumseh motors, that have an allow flywheel. This isn't a huge deal. I wish snow blower had the alloy flywheel, but they don't. It's OK though. It's not as big a deal as some may think.

I should also mention that i am by NO MEANS an expert on vintage Tecumseh flat heads. All i can tell you is what has worked for me (in the following posts.) There's a lot of compromises that will drive the "purists" crazy. I'm sorry about that. But here we go....
 
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cfh

Well-Known Member
#2
With all that in mind, i bought a 4hp Tecumseh in an Ariens snow blower this week for $50. It looks like the motor is from 1975 (it's a points and condenser model.) I will go through what i do to make it "mini bike ready" in the following posts. Hopefully you'll find this helpful.

First after removing the motor from the snowblower, I remove all the metal snow guards. The big one covers the carb. Take this off and you'll see there's no air cleaner (snow blowers don't have them.) Also there's often snow guards on the top side of the pull start. Discard all these snow guards, you won't need them. All these guards should and can all be easily removed. Take off the original carb (you won't need it). And if there's any gear on the PTO(s), remove that too. Also remove the exhaust and set it aside (we will re-use it.) If the model has an attached gas tank (usually they do), take that off too and set it aside.

I take the pull start blower housing off now. And any another metal sheilds. And the gas tank metal bracket(s). Now is a good time to buy an air cleaner assembly. That includes the body (#31715), mounting plate bracket (#31691), gasket (#27272) and element (#30727). Often you can find these used. But they are available from OldMiniBikes brand new.

At this point, i take all that metal down to my local powdercoat guy. He sandblasts them and coats them. Cost is $20 to $35, depending on his attitude for the day.

So with this in mind, you need to pick a motor color. The powdercoat guy will ask! So it's decision time. Here's some things to consider...

No matter what color you pick, do *not* go with GLOSS. Don't do it. Well i guess if you want a "show bike" fine. But if you going that route, you won't be using a snow blower motor! I am of course assuming you are doing this to end up with a working and usable motor. Not some "autorama" thing.

Gloss finishes suck. don't use them. They don't wear, and any sort of scratch will stick out boldly. Also any imperfection in the metal will stick out boldly. So don't do it. Use a satin finish. A scratch in the finish is far less obvious, the finish wears better, and lastly, the motor is more versatile.

what do i mean by that? Well if you have a lovely gloss finish, and you put that motor in a "survivor" minibike, it will look stupid. Like completely dumb. A satin finish is just more versatile. You can put that motor in a fully restored bike, or a survivor, and it will look fine and dandy in either bike.

Also in regard to color... Well black is black, no questions there. But white, what about white?? Personally i go with an off-white finish. Bold white again will look really stupid in a survivor bike. So i go off-white, it looks clean and nice, but not too sterile. It will work in a show bike or in a survivor.

Here's the color and finish my powdercoat guy put on my removable metals....
Oh and why the powdercoater? Screw paint. Paint is not durable, it's poison, it's a pain in the ass, and it's expensive. I'm spoiled and have a powdercoat guy a mile from me. But powdercoat is far more durable and totally gas resistant. And i don't have the breathe any poison overspray. It's the way to go!

Note on the pull start, unless you want to take it fully apart, you can't powdercoat it. It's the one removable part i end up painting (sadness.) Mostly because i just don't want to wind up the spring! Also i always replace the nylon cord, because it always seems too short. But you can do that without taking it apart. Also i put a mini bike style pull handle on the pull start. Many snow blowers have this huge pull thing. New handles are available and are cheap, part #590387

 
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cfh

Well-Known Member
#3
Unless your powdercoat guy is amazingly fast, you'll probably have to wait a bit to get those parts back. So in the mean time, we'll deal with the motor block. I remove the flywheel. Mostly because i want to service the points/condenser. But for what we're about to do, you really need to have the flywheel off anyway.

What i do is go down to my metal shop and borrow their sand blaster. I like to blast the short block. Especially if you're changing the motor color! In this case the Arien snow blower motor color is white, but still i like to blast all the old crap off the motor, and start fresh. Personally i don't blast the crap out of the motor. I just do a minimal job. Enough to get the crust off. Here's the block after i do a quick blast. Don't forget to plug all the holes to keep the sand out! leave the oil in the motor too!! You'll change it *after* the blast.

Make sure you have the head bolts installed and a little tight. You'll want to blast those too.

Note this motor had a second small PTO. you can barely see it in the picture below. How did i make it go away? I got the motor running, and put a hacksaw blade on the shaft. Since it's turning, it cuts off the extra small PTO nice and clean. Sure you could remove it from the inside and get a new side cover. But why bother? This is an easy solution and you'll completely forget that extra PTO was even there!

 
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cfh

Well-Known Member
#4
Now it's time to paint. Yeah i know, i hate paint. But you can't powder coat the short block! Now you do have a choice here. You can STOP and not paint the short block! that is essentially what Tecumseh did starting in the 1990s. They just painted the removable metal, and left the short block "naked". That's not a bad choice! And it avoids any painting.

But for my needs, i want a painted short block. It's more "vintage". A lot of guys use two part urethane and a color basecoat. That's cool but not my cup of tea. That stuff is violent and nasty and expensive. Instead i go with Epoxy spray paint, available at Home Depot in a spray can. Don't go nuts in the painting! The less paint the better, just the bare minimum to cover! Also it's really important to let the Epoxy paint dry for at least 48 hours. It really takes that long before it's gas resistant and durable. Again i'm using off-white (not pure white.) Here's the motor painted.

 
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cfh

Well-Known Member
#5
Next up is dealing with the carb. You will need a new carb, the snow blower one won't work. Personally i get the ebay cheapo version. I've had really good luck with them. And at $10, you can't beat it. Tecumseh #632230 or #632272. You will have to drill a 1/16" hole in the throttle butterfly mech for your metal linkage.

Note i DO NOT paint the carb! i know a lot of guys do that, but i do not. I think it's a bad idea. There's too many small moving stuff that can get clogged with paint. It's not worth it. And i like the look of the carb in it's metal finish.

You will also need a new minibike throttle assembly. OldMiniBikes sells it. Tecumseh 730136a. Don't cheap out, get this part. It is available. You will have to drill out the rivets holding the old throttle assembly (do this when the flywheel is removed, though it can be done without the flywheel removed.) use a 3/16" drill bit. Then attach the new throttle mech with 8-32 screws 3/4" long and locknuts.

Before you install the flywheel and blower housing, install a new 1/4" fuel line. Though not difficult, it's just easier to do with the flywheel off. I use black double walled line. Do not use CLEAR fuel line. That blue or red stuff is pretty, but don't use it!

 
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cfh

Well-Known Member
#6
Now what about the governor? Personally i don't delete it, i leave it. BUT i do wire it with a straight wire. This way the governor is essentially removed. But if you replace the straight wire with a spring, you're back to having a governor! Very versatile!!

 
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cfh

Well-Known Member
#7
Oh i kind of forgot to mention this... when you have the flywheel off and you're installing a new condenser (required!!!) and checking/replacing the points, you should add a kill switch wire. It goes right on the bolt that holds the points in place (and where there should be 2 other wires attached.) I also bolt another ground wire to the screw that holds the metal sheild. So there's two wires going to a .093" Molex connector with round pins. This way i can hook up a kill button later (or not.) Why the ground wire? because if your handlebars (where the kill switch goes) is insulated, you have a ground wire for the kill switch. You don't have to use it, but it's nice to have. Also if you use a toggle style kill button (opposed to a push-and-hold-down style button), the remote ground wire is required. Personally i like the db30 style kill switch which is for sale on ebay.

Also on the gas tank i always install a right angle fuel shut off. These are available for cheap on ebay. It's a nice touch (though not stock). You'll thank me if you have it! also buy new fuel line clamps. Again i got a bag of 100 of them on ebay for next to nothing.

 
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cfh

Well-Known Member
#8
Now it's time to think about engine stickers. Some guys use water slide decal style, and put it under the paint. Since i'm not using paint (powder coat), i can't do that. Well to be frank, even if i was using paint, i would still not use water slide decals. Because if they get scratched, you're screwed!

Instead i use vinyl decals for this task. If they get damaged, i just peel it off and put on a new one! It's far more versatile and cheaper. My vinyl guy makes a sheet of decals for me and i just cut them to size. Then peel and stick! There are scans of these on pinrepair.com/minibikes in photoshop format. You can download them and print them.

 
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cfh

Well-Known Member
#9
I wire wheel the snowblower exhaust and paint it black with heat resistance paint. It will look nice for about 3 days! no really there's not much you can do because it gets so hot. I do install the exhaust with stainless steel bolts 1/4-20. Don't use the originals with a phillips head. You'll thank me later on this...

But here's the motor all done and ready for action!

Note i did not cover any internal rebuild stuff in this article. You can do that if you want. I do some of it. But for the most part, these snowblower motors are lightly used, and frankly, don't need a lot of rebuild to the internals. I do remove the head and check the values and bore for any wear/scratches. On snowblowers, even ones from the 1970s, they seem pretty darn new inside. I wire brush off the carbon inside the head and on the values. No particular reason for that, other than it makes me feel better.

 
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cfh

Well-Known Member
#10
another angle.... Note i put the lubrication decal on the side of the blower housing away from the gas tank. Just in case you spill some gas, i like to keep the decals as far away from the tank as possible.

 
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cfh

Well-Known Member
#13
and if you prefer, here's one in satin black. All the same procedures, just a different color. Again don't use gloss black, you will regret it.



OK fine so you're hell-bent on gloss black powdercoat. Here's one i did in gloss black. YECK. No really, you have to admit, the satin finish motor does have a better look. (Also this is a newer "cyclone" pull start model motor.) you may ask yourself, "why is the lubrication decal on the front of the blower housing?" Well there's good reason for that! Underneath the decal is a hole! Some snowblowers have holes in the blower housing for a primer bulb. Instead of welding the hole shut and grinding it smooth, i just decal over it. See you didn't even know there was a hole there, did you??? ha!

 
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cfh

Well-Known Member
#14
And here's an army of motors, ready to go on bikes! Note there's a few with cyclone pull starts and old decals. They look pretty good too!

 
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cfh

Well-Known Member
#15
I should add one more thing... If the PTO is not 3/4" or is tapered, there is a solution. I have a machine shop that will take my old crank and turn it down to .750", and bridgeport a new keyway. Or you can buy a new crackshaft on ebay #34734 (i think!) for a 5 hp motor. That's a solution too. Obviously you'll have to disassemble the motor to change the crankshaft! it's work, but fun. i've done it a few times...

The two shafts on the right were re-worked (they were both tapered shaft). Used a metal lathe and cut the shaft down to 3/4". Then used a bridgeport to put a new keyway channel in the PTO. The one on the left i bought off ebay and was 3/4" stock from the factory.

 
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cfh

Well-Known Member
#16
Now for the last thing, what about drilling/taping the PTO? You know, so you can put on a clutch and bolt it in place (opposed to set screws.) This is pretty easy. The PTO is cast steel, which in reality, is pretty soft (and self lubricating while drilling.) Since we're going to go with a 5/16-24 screw size, you'll need a 5/16-24 tap and tap handle. You'll also need a couple drill bits (1/4" and 17/64", though technically, it's really a letter "I" drill bit, but 17/64" works fine.)

You also need a centering tool. I bought mine from McMasterCar for $15. It works well and is drilled for 1/4". (insert name of tool and part number here.) You just slide the tool into an old clutch, put it on the PTO, and drill 3/4" deep into the PTO shaft. (The clutch is just holding the tool in place, it serves no other purpose in this exercise.) Then remove the clutch and tool, and use the 17/64" bit to enlarge the hole slightly. Then tap it with the 5/16-24 tap. Now your PTO is ready for a clutch. All you need is a 5/16-24 bolt and washer.



 
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cfh

Well-Known Member
#17
I hope people find this thread helpful in obtaining and restoring a Tecumseh minibike, without a lot of effort or money. I know it's not the preferred way of doing this, but i find it to give really good results. Any comments are appreciated. thanks!
 

capguncowboy

Well-Known Member
#18
I appreciate your insight and I believe it will help a lot of people with their restorations to know some alternative options.

However, I can't understand why you place the oil decal on the front of the engine. If there are holes, why not fill them? You're gonna go through all the trouble of restoring an engine, why not go 1-2 steps further and put a backplate on the housing and put down some Bondo? I think the placement of your decals take away from an otherwise great job. Just my 2 cents
 

cfh

Well-Known Member
#19
Because powder coat does not stick to Bondo. The hole would have to be Fill welded and then ground flush. So not impossible there’s risks involved in doing that and obviously time and expense
 
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