Jans Ridiculous Zero-Cost Kart Project

JanSolo

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Hello, wise elders!

I'm stuck at home and wanted to do something fun, so I'm teaching myself how to weld. My first project is to try and build a cheap-n-dirty kart with as few purchased components as possible. Zero cost is the goal. It's all just for fun, so it doesn't have to be fast or optimal in any way.

So far, I have:
1. a Briggs 4.5hp lawnmower engine (works, but is vertical unfortunately)
2. a peerless 718 gearbox. (donated by a kindly ride-mower repairist)
3. a peerless 100 diff (not sure if I need this)
4. a few chains and sprockets of various sizes.
5. various bits of steel that I might be able to weld up into a frame

I have MANY questions, o wise elders, so it would be cool if you could shine some wisdom over my way. I really have very little idea of what I'm doing.


1. My engine is vertical, however the P700 has a right-angle drive build into it. I was planning on using this to correctly orient power to my axles. I'm ok with just leaving the P700 in gear while I drive.
My question is: Can I mount the P700 upside down so that the input shaft faces up? That would make it much easier to mount to my vertical engine. Otherwise, I'd need a vertical jackshaft & sprockets to get power to the input shaft; I'd like to avoid that if possible. Simple is better right?

2. Clutches. I'm going to need some kind of centrifugal clutch. Do you know what kinds of things have centrifugal clutches in them that could handle kart-sized torque? Is there anything? Any places I could pick one up used/scrap/etc? I'll buy one if I have to, but we're aiming for zero cost here.

3. Flywheels. I read on here somewhere that lawnmower engines need bigger flywheels to compensate for the removal of the blade. Is there any more info on this? What size/weight flyweel should I get? Can I just put it on the output shaft of the motor? Is it dangerous having a large spinning mass outside of the engine like that? Any precautions?

4. What order should things go together? My initial plan was to have the engine go into the clutch, clutch output goes on the P700 input, P700 output goes to live axle (or P100 diff; should I use this? does it gain me anything?), Axle has a brake on it and both rear wheels.
Does this sound sane? Some people suggested putting the clutch on the output of the P700; should I consider this?

5. Wheels. What's a good source of decent wheels & tires for next to nothing? I'm planning on checking scrapyards, mower repair places, etc. Anyone have any tips on what kinds of wheels to get and where I might find them? My ride-mower repair buddy is keeping an eye open for me.

Thanks again, o wise kart elders!

Cheers

Jan
 

Karts of Kaos

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5. Wheels. What's a good source of decent wheels & tires for next to nothing? I'm planning on checking scrapyards, mower repair places, etc. Anyone have any tips on what kinds of wheels to get and where I might find them? My ride-mower repair buddy is keeping an eye open for me.
i don't know of any where, junk yard sound good. just don;t get hf wheels
 

Smerft85

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Heh! Not a fan of Harbor Freight, eh? Not to worry, we don't have em up here in QC.

Na, most of us are fans of the $99 predator engines from harbor freight, but the cheap wheels disintegrate quickly and seem to be the go-to for the inexperienced.

For wheels and tires you could find a broke down lawn tractor cheap, amazon, bmikarts.com, gopowersports.com, ebay, or several other sites, would also like to add that a set of split wheels would be a good investment and you'll thank yourself later with the tire changes.
 

JanSolo

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Thanks for the tips. My current plan is to somehow 'acquire' some used lawn tractor wheels. Might be a bit big and heavy considering the engine I'm using though.

a set of split wheels would be a good investment and you'll thank yourself later with the tire changes.

What are split wheels? The rims split in half? Isn't that inviting leaks?

cheers.
 

Smerft85

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What are split wheels? The rims split in half? Isn't that inviting leaks?

cheers.

Two piece wheels that split down the middle, there are many that can be tubeless, if nothing else use tubes in them for extra reassurance. When you wear out tires or blow one they are much easier to work with than a solid wheel. My dingo has tubeless two piece aluminum wheels and they hold air just fine.
 

anickode

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Be wary of riding mower wheels for the front. They often have bronze bushings instead of bearings, which will last a lifetime at 4mph, but only about 5 minutes at 30mph.

Some good quality one piece 6" hand truck wheels would do just fine for the front of you put high speed bearings in them. That's what I've been running on my budget kart, and they've done quite nicely.

As for the rears, I'd find some riding mower wheels that will fit your axle.

Being mower parts, the gearing will be quite low, and you'll need the bigger tires to get any kind of speed out of it.

For a clutch, you really need to just break down and buy a V belt centrifugal clutch. Chains do not do well on their side. Run a belt centrifugal clutch with a 1:1 pulley ratio to the gearbox. If you are unhappy with the speed, put a bigger sprocket on the gearbox output instead of trying to overdrive the input.
 

Kaptain Krunch

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Hello, wise elders!
1. My engine is vertical, however the P700 has a right-angle drive build into it. I was planning on using this to correctly orient power to my axles. I'm ok with just leaving the P700 in gear while I drive.
My question is: Can I mount the P700 upside down so that the input shaft faces up? That would make it much easier to mount to my vertical engine. Otherwise, I'd need a vertical jackshaft & sprockets to get power to the input shaft; I'd like to avoid that if possible. Simple is better right?

2. Clutches. I'm going to need some kind of centrifugal clutch. Do you know what kinds of things have centrifugal clutches in them that could handle kart-sized torque? Is there anything? Any places I could pick one up used/scrap/etc? I'll buy one if I have to, but we're aiming for zero cost here.

3. Flywheels. I read on here somewhere that lawnmower engines need bigger flywheels to compensate for the removal of the blade. Is there any more info on this? What size/weight flyweel should I get? Can I just put it on the output shaft of the motor? Is it dangerous having a large spinning mass outside of the engine like that? Any precautions?

4. What order should things go together? My initial plan was to have the engine go into the clutch, clutch output goes on the P700 input, P700 output goes to live axle (or P100 diff; should I use this? does it gain me anything?), Axle has a brake on it and both rear wheels.
Does this sound sane? Some people suggested putting the clutch on the output of the P700; should I consider this?

5. Wheels. What's a good source of decent wheels & tires for next to nothing? I'm planning on checking scrapyards, mower repair places, etc. Anyone have any tips on what kinds of wheels to get and where I might find them? My ride-mower repair buddy is keeping an eye open for me.

Thanks again, o wise kart elders!

Cheers

Jan

1: I would avoid mounting the 700 upside down, the input shaft has a small roller bearing that needs lubrication. Additionally, people who use these in racing mowers do some prep work for the increased RPM. A vent needs to be added, and the grease should be swapped for gear oil. Some serious racers remove the reverse chain, but i dont think thats necessary for such low HP.

-Side note, why would you need a vertical jackshaft? mount the engine and trans on the same plane - belt from engine to trans, easy as that.

2: Centrifugal belt clutches are found on some equipment, chippers often have them, DR power wheel barrels...but honestly on a budget build, i would make a belt tensioner style clutch as found on a lawnmower. Very simple rugged design. Racing mower forums will have lots of info on building one correctly (belt guide location is critical!).

3: If this is a push mower engine it will have an aluminum flywheel, which may make the engine hard to start, or not start at all. If the engine runs, without the blade, i wouldnt worry about it. If you are having trouble, you will have to find the same engine intended for a different purpose, with a cast iron flywheel instead of aluminum. Do not mount it on your crankshaft, simple remove the old and install the new.

4: Do not put the clutch on the 700 output, it wont spin fast enough to engage. If i were building this, i would do a belt tensioner style clutch between engine and 700 input, with an overdrive ratio. Most racers prefer to gain axle RPM by increasing the 700 input speed, rather than through gearing on the output (less torque on the input shaft in theory).

-Brakes on axle, trans brakes are dangerous. The peerless diff can be used if you like, i prefer a solid axle but that diff will allow you to turn tighter.

5: Wheels, if you use front mower rims you will have to remove the bronze bushings and find bearings to fit.
Rear rider wheels can be used, often come in a 3/4" or 1" keyed bore.
 

Smerft85

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20200112_160303.jpg

All four, mower wheels. Fronts have flanged bearings ordered from Amazon. If your going to use handtruck wheels you may as well get the junk $3.99 wheels, they'll hold up about the same.

P.S. we still await a picture to see what you have in mind...
 

JanSolo

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1: I would avoid mounting the 700 upside down, the input shaft has a small roller bearing that needs lubrication. Additionally, people who use these in racing mowers do some prep work for the increased RPM. A vent needs to be added, and the grease should be swapped for gear oil. Some serious racers remove the reverse chain, but i dont think thats necessary for such low HP.

Yes, I saw your post on that; I'll definitely be doing this. Is there a part number for the oil seal that's needed for the input shaft?

-Side note, why would you need a vertical jackshaft? mount the engine and trans on the same plane - belt from engine to trans, easy as that.

Didn't think of that; thanks!

2: Centrifugal belt clutches are found on some equipment, chippers often have them, DR power wheel barrels...but honestly on a budget build, i would make a belt tensioner style clutch as found on a lawnmower. Very simple rugged design. Racing mower forums will have lots of info on building one correctly (belt guide location is critical!).

This is good info; I would not have considered doing this without yoru advice. Isn't it a lot more work to build a belt tensioner setup than just attaching a centrifugal clutch up to something and slinging a chain on it?
I'll need to check out some example photos.


3: If this is a push mower engine it will have an aluminum flywheel, which may make the engine hard to start, or not start at all. If the engine runs, without the blade, i wouldnt worry about it. If you are having trouble, you will have to find the same engine intended for a different purpose, with a cast iron flywheel instead of aluminum. Do not mount it on your crankshaft, simple remove the old and install the new.

Again, great info. Thanks!
Is it even possible simulate the extra weight by adding a rotating mass to the output shaft? Or is that just a waste of time?

4: Do not put the clutch on the 700 output, it wont spin fast enough to engage. If i were building this, i would do a belt tensioner style clutch between engine and 700 input, with an overdrive ratio. Most racers prefer to gain axle RPM by increasing the 700 input speed, rather than through gearing on the output (less torque on the input shaft in theory).

-Brakes on axle, trans brakes are dangerous. The peerless diff can be used if you like, i prefer a solid axle but that diff will allow you to turn tighter.

All the karts I've seen in person have solid axles with disc brakes mounted on them. That was my plan also.
If I used the diff, I'd need two discs and two calipers, right? One for each halfshaft.

5: Wheels, if you use front mower rims you will have to remove the bronze bushings and find bearings to fit.
Rear rider wheels can be used, often come in a 3/4" or 1" keyed bore.

Bearings, not bushings; got it.


Thanks Kaptain K! I really appreciate your detailed answers.
Now I need to do some serious scrounging to see what parts I can come up with.
 

Kaptain Krunch

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Yes, I saw your post on that; I'll definitely be doing this. Is there a part number for the oil seal that's needed for the input shaft?



Didn't think of that; thanks!



This is good info; I would not have considered doing this without yoru advice. Isn't it a lot more work to build a belt tensioner setup than just attaching a centrifugal clutch up to something and slinging a chain on it?
I'll need to check out some example photos.




Again, great info. Thanks!
Is it even possible simulate the extra weight by adding a rotating mass to the output shaft? Or is that just a waste of time?



All the karts I've seen in person have solid axles with disc brakes mounted on them. That was my plan also.
If I used the diff, I'd need two discs and two calipers, right? One for each halfshaft.



Bearings, not bushings; got it.


Thanks Kaptain K! I really appreciate your detailed answers.
Now I need to do some serious scrounging to see what parts I can come up with.


The tensioner clutch is more work, i however its pretty simple in my opinion. Regardless of which route you go, some form of tensioner should be installed. You wont be able to reliably run a chain horizontally, and static tension tends to kill belts quicker. If i were to run a centrifical belt clutch, i would still build a spring loaded tensioner.

As far as adding rotating mass to the crankshaft...yes it will work, but whatever you use will need to be balanced...and i mean seriously balanced, a 5lb weight spinning at 3600 rpm is no joke. I would strongly recommend a different flywheel.

As far as 2 discs on a differential axle....yes you would want 2 for adequate stopping power.
 

JanSolo

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Update:

I took the mower cutter off and started the motor. It runs OK; idles a little rough; I put that down to the carb needing a clean/replacement; I haven't touched the internals yet.
Kaptain_K mentioned above that I only need to increase the flywheel weight if the engine won't idle without the blade. Since it seems to idle ok, I'm going to leave the flywheel as it is for now.

I had to clamp the flywheel brake open very firmly to get it to run properly. This brake is attached to the mower handle; it kills the mower if you release the handle. I really want to remove the flywheel brake, but then I'm not sure how to stop the engine... Currently, I just release the clamp and it stops immediately. If I remove the brake, I'd need another way to turn it off; what's the normal approach here?
I was thinking of adding a switch to the spark circuit, so I could cut off the spark to disable the engine. Is this a good idea?

Next question for you wise kart elders: How do I add a throttle to this engine? It's a mower engine, so theres no way to get it revving more than spec. Do I need a new carb? Can I hack the existing one? I'm new at this, so I'd appreciate your vast wisdom!


Cheers

Jan
 

anickode

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To kill the spark, there should be a small wire (not the plug wire) coming off the magneto that goes to the kill mechanism on the brake. It doesn't just apply the brake to bog down and stall the engine. The brake is there because the government decided mower blades should stop within 2 seconds of shutting off the engine. Anyway, you can take THAT wire and run it to a toggle switch. It shorts out the magneto so it can't create a spark.

As for the speed, that may be tricky as the carb is not only meant to not be variable speed, but also not meant to idle. You can remove the governor linkage and hook the throttle directly to the carb butterfly, but if the carb doesn't have an idle jet, you may have to fit a different carburetor.

Alternatively, you could replace the governor spring with a weaker one (how much weaker, who knows) connected further down the governor arm (closer to the governor shaft). That will lower the baseline rpm to idle speed, and then use the original governor spring in its original location on the governor arm, and connect your throttle cable to that. It would take some fiddling, but you CAN make that governor operate as a variable throttle. The mechanism is the same, just the spring arrangement is different. Again though, if the carb lacks an idle jet, you'll have to fit a different carburetor.
 

JanSolo

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To kill the spark, there should be a small wire (not the plug wire) coming off the magneto that goes to the kill mechanism on the brake. It doesn't just apply the brake to bog down and stall the engine. The brake is there because the government decided mower blades should stop within 2 seconds of shutting off the engine. Anyway, you can take THAT wire and run it to a toggle switch. It shorts out the magneto so it can't create a spark.

Excellent! Thanks, I will do this.


As for the speed, that may be tricky as the carb is not only meant to not be variable speed, but also not meant to idle. You can remove the governor linkage and hook the throttle directly to the carb butterfly, but if the carb doesn't have an idle jet, you may have to fit a different carburetor.

Great info; thanks.
Where is the idle jet and what does it look like? I'm going to take it apart tomorrow and have a look.

I'm not 100% sure how the govenor works; although I did notice several threads here discussing how to remove them. Presumably, it's to keep the engine running at whatever the set rpm is regardless of load. Once I get a working throttle, I imagine I'll also have to remove the gov, right?


Alternatively, you could replace the governor spring with a weaker one (how much weaker, who knows) connected further down the governor arm (closer to the governor shaft). That will lower the baseline rpm to idle speed, and then use the original governor spring in its original location on the governor arm, and connect your throttle cable to that. It would take some fiddling, but you CAN make that governor operate as a variable throttle. The mechanism is the same, just the spring arrangement is different. Again though, if the carb lacks an idle jet, you'll have to fit a different carburetor.

Interesting idea; I might try it out once I've figured out if my carb has an idle jet or not.

Thanks again for the detailed answers! Really helps me figure this stuff out. Loving the community here!

Cheers.

Jan
 

JanSolo

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Additionally, people who use these in racing mowers do some prep work for the increased RPM. A vent needs to be added, and the grease should be swapped for gear oil.

I followed your advice and cracked open the 700; scooped out all the grease and cleaned it up with some gas. I made some interesting discoveries!

It seems the gearbox has been rode hard and put away wet; It was full of water! The grease seems to have spared most of the parts from damage, however there were a few spots that look corroded.

This is the large reverse sprocket; 4 teeth are chewed up. This is probably the worst damage I found. I'm tempted to pile a fat weld bead on there and file it down to the original profile; is this crazy talk? I should probably replace this guy, right? Unless I just skip reverse and remove the whole caboodle.

This is the large gear on slotted shaft; 3 teeth have minor pitting. Thinking of just leaving this as is.

This is the reverse chain; a couple of the link barrels are pitted, and one barrel is about 30% missing. Again, thinking of leaving this; I don't think it compromises the strength of the chain as the links are all undamaged.

Also, The output shaft sprocket has one tooth missing. This will likely need repair or replacement, no? Think I can repair this with a welder and a file? Will a weld-over fix be strong enough?
 

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landuse

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That one chain link looks like it is actually cracked. I am not too sure if i would trust that.

Welding onto a sprocket often has the affect of heat weakening the rest of the sprocket. If you can order new and they are cheap enough....I would do that rather.
 

Kaptain Krunch

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The cool thing about these peerless lawnmower transmissions/transaxles is that they often share parts. Check around lawnmower repair shops, even if you find a completely different peerless model it may have the chain/gears/sprockets you need. If you were closer id let you come pick through my junk pile. I scrapped over 8k lbs of lawnmowers and parts last year...
 

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What kind of lawn mower transaxle is this because if it is a hydrostatic, then that means it is an automatic and only 1 speed and won't get you past about 7mph
 

JanSolo

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What kind of lawn mower transaxle is this because if it is a hydrostatic, then that means it is an automatic and only 1 speed and won't get you past about 7mph

It's a peerless 700 gearbox... specifically a Tecumseh model 718 as mentioned in the first post.

I'm told that these things are used in race karts; so I imagine it's possible to make them go quick. Having said that though, the goal here is to learn me some mech skills and to have a good time. So even if I end up with a kart that only does 7mph, hey, I'm cool with it!

---------- Post added at 02:24 PM ---------- Previous post was at 02:07 PM ----------

If you were closer id let you come pick through my junk pile. I scrapped over 8k lbs of lawnmowers and parts last year...

Holy crap; that's a lot of old bits! I guess you do this for a living, then? No wonder you know so much about these old transmissions.

I've a question about something you mentioned above regarding a Belt-Tensioner Clutch... Is there a plan or a 'right way' of doing this? Even a few pictures of one would be helpful... I'm trying to design my driveline and I want to plan out what I need.

Cheers

Jan.
 

anickode

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It's a peerless 700 gearbox... specifically a Tecumseh model 718 as mentioned in the first post.

I'm told that these things are used in race karts; so I imagine it's possible to make them go quick. Having said that though, the goal here is to learn me some mech skills and to have a good time. So even if I end up with a kart that only does 7mph, hey, I'm cool with it!

---------- Post added at 02:24 PM ---------- Previous post was at 02:07 PM ----------



Holy crap; that's a lot of old bits! I guess you do this for a living, then? No wonder you know so much about these old transmissions.

I've a question about something you mentioned above regarding a Belt-Tensioner Clutch... Is there a plan or a 'right way' of doing this? Even a few pictures of one would be helpful... I'm trying to design my driveline and I want to plan out what I need.

Cheers

Jan.

You can look up a parts diagram for any cheaper riding mower to see what they're about.

You should really check out a lawnmower racing forum... They'll have just about all the info you could possibly ever need and more.

And used in racing karts, no. But racing mowers? It's the go-to gearbox.
 
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