Some questions about a first build.

[Bigblockguy]

Lol. I def feel you on the lifetime of abuse, but yes, i think if i can work ot where to put my feet the rest will be easy. Ive got a good idea how to build the back and main frame, just need to work out the exact numbers

 

[Millwright]

Well I don't know about you guys, but for me , there is nothing wrong with having too much material on hand. There is always " another project" of some sort.
I bought three lengths, will probably only use two.

 

[Bigblockguy]

Just by doing a simple layout using 1" square for everything on the main frame except the cross bar for the wheel mounts and the area behind the seat which will both be 1 1/2 as well as the rear section, i came up with a rough estimate of 37ft of 1" and 18ft of 1 1/2". It might not be light, but itll be strong enough to take whatever i throw at it.

 

[madprofessor]

(1): What thickness/gauge are you planning for the 1"? Reason I ask is because I really like to see a quality truss frame get built, but have seen the double run of trussed tubing wasted by using really heavy steel. Makes a truss design unnecessary. The idea of a truss frame is to bridge the long spans with very thin/less costly tubes and still end up with a very stiff frame build. It's all in the little diagonals, provided that they are staggered opposed to each other.
(2): You can see in pics of my kart the length of the 1.5" sections I made, basing that visual on fact of 8' wheelbase. If it helps your estimation of strength/length, know that all of it you can see is so stiff it could fall off a building and wouldn't even flex, much less bend. Stupidly overbuilt.

 

[Bigblockguy]

(1): What thickness/gauge are you planning for the 1"? Reason I ask is because I really like to see a quality truss frame get built, but have seen the double run of trussed tubing wasted by using really heavy steel. Makes a truss design unnecessary. The idea of a truss frame is to bridge the long spans with very thin/less costly tubes and still end up with a very stiff frame build. It's all in the little diagonals, provided that they are staggered opposed to each other.
(2): You can see in pics of my kart the length of the 1.5" sections I made, basing that visual on fact of 8' wheelbase. If it helps your estimation of strength/length, know that all of it you can see is so stiff it could fall off a building and wouldn't even flex, much less bend. Stupidly overbuilt.

Its 1/8" wall. It might be marginally thinner. I wasnt planning on trussing it like a bridge. Im gonna put an x between the front where my feet sit and the back where the frame hinges, and then the top rail which is gonna end somewhere behind my feet would have a few diagonal supports between it and the bottom rail. So i guess not a true truss? The benefit of being in a fab shop. If it breaks i dont have to pay someone to fix it, but mind you, im putting heavier steel and gusset plates where its gonna take the most beating. The x braced frame should be enough to handle anything i throw at it on a trail, the upper rail would take out a lot of the stress if and when the front end leaves the ground. The hinged rear im using motorcycle shocks from a harley thatll connect to, idk, 12-14 inch shock towers on either side of the seat. They only have 4" of travel at most, and ill be employing bump stops to keep my gas tank from ever colliding with the back of the seat.

 

[madprofessor]

Once the basic frame's welded up, a good bounce test to check the flex of the long sections will tell the tale. Here's a proven mechanical cheat for you.......................
If it has more deflection than you like, the thinnest and lightest of angle iron sistered up to it and tacked on in close spacing is all it takes to give square tube of the same width hugely more stiffening support. Lighter weight for only having 2 sides instead of 4, and also lighter weight per each flat side because it's thinner.

 

[Bigblockguy]

Once the basic frame's welded up, a good bounce test to check the flex of the long sections will tell the tale. Here's a proven mechanical cheat for you.......................
If it has more deflection than you like, the thinnest and lightest of angle iron sistered up to it and tacked on in close spacing is all it takes to give square tube of the same width hugely more stiffening support. Lighter weight for only having 2 sides instead of 4, and also lighter weight per each flat side because it's thinner.

Thanks. I doubt a double rail run from behind the seat up to the steering crossmember is gonna have much flex over 43 inches. I also did some calculations off bmi. On 22s with a 6 to 1 ratio on an ungoverned 5500rpm, not accounting for weight or the tc, i should theoretically hit 60. 40 at a governed 3500.

 

[madprofessor]

Hope that works for you better than my plan did. My big heavy kart-accidentally-turned-buggy so to speak should really kick it down the trail also, the 6.5 hp. 212 being hotrrodded up to 15+ hp.............Much to my chagrin however, I've learned that all that power I counted on won't hardly even start to appear until I reach over 4K rpm at least. Currently struggling to make it able to get there.
You've got about 13 hp. right off the line, yours ought to boogie woogie.

 

[Millwright]

I'm taking the above post as "encourageing news"
I've set up with a 3.7 ratio, but have much smaller wheels, and a 420cc. Although it's probably the same HP.

 

[Bigblockguy]

Hope that works for you better than my plan did. My big heavy kart-accidentally-turned-buggy so to speak should really kick it down the trail also, the 6.5 hp. 212 being hotrrodded up to 15+ hp.............Much to my chagrin however, I've learned that all that power I counted on won't hardly even start to appear until I reach over 4K rpm at least. Currently struggling to make it able to get there.
You've got about 13 hp. right off the line, yours ought to boogie wo

Hope that works for you better than my plan did. My big heavy kart-accidentally-turned-buggy so to speak should really kick it down the trail also, the 6.5 hp. 212 being hotrrodded up to 15+ hp.............Much to my chagrin however, I've learned that all that power I counted on won't hardly even start to appear until I reach over 4K rpm at least. Currently struggling to make it able to get there.
You've got about 13 hp. right off the line, yours ought to boogie woogie.

Thats why i snatched up the motor i did. The wheels are just bc thats whats laying around. I like saving money. But i was thinking about your cart earlier. Its def overbuilt and the motor is really too small for all that weight, plus you and maybe someone else. Im sure its fine for around the yard, but that motors maxed out and still strained. Now if you put a v-twin on it itd rip.

 

[madprofessor]

Sure couldn't afford a V-twin for good ole "SchizoBallz", but I've been researching Predator 420's ($400) and series 40 CVT's for them. Only real hold-back is that current hotrod motor would transfer to next build, "BareBallz".
Already have 6" split rims with 12" tall tires for it, and it's supposed to be a bare minimum cost skeleton sort of wheelie machine, just see how much I can get for how little money. This hotrod motor would make that barely-there lightweight machine terrifying dangerous, and I've promised our Boy Scout troop I'll keep it awhile, let them use it around the church at weekly meetings, and take it on campouts.
Ain't yankin' out nary parts, y'all. Has .020-over ARC rod, crankshaft clearanced for it, .012 ss head gasket, Superman 265 cam, PVL 28 degree flywheel, 22 lb. valve springs, hi-perf coil, .022 low and .036 jets, Walbro fuel pump, master top plate kit,..................etc.
I need a $500 tax-free windfall. Another $140 would put a stock 212 in "BareBallz".

 

[karl]

Its def overbuilt and the motor is really too small for all that weight, plus you and maybe someone else. Im sure its fine for around the yard, but that motors maxed out and still strained. Now if you put a v-twin on it itd rip.

Yeah a new 670 predator is expensive, but call/ look around locally. The deals are not going to be supplied by harbor freight or
large kart sites.

I built a spicy 674cc kohler command V-twin for less than $220, the motor/block was from a junkyard 2000 series
cub cadet lawn mower. Paid bout $50 for it, pull yourself.

Also 40 series is great for big singles, but not so hot for twins 16hp+. I used a UTV driver+ 1 1/4 belt,
and snowmobile driven for my kart. Cost= $0. 20 year old belt still looks like new.

 

[Millwright]

MadPro, did you build that engine up yourself?
Sounds like a beast for sure. Just crying for a nice light weight kart frame!
I don't know much about it, but my gut feeling is to go with displacement and gearing for speed.
These tricked out high rpm clones give me an edgy feeling that they are going to spin apart at any time!

 

[Bigblockguy]

MadPro, did you build that engine up yourself?
Sounds like a beast for sure. Just crying for a nice light weight kart frame!
I don't know much about it, but my gut feeling is to go with displacement and gearing for speed.
These tricked out high rpm clones give me an edgy feeling that they are going to spin apart at any time!

While the predator series doesnt have the same rep as honda does, ive seen some pretty damn good motors built by guys that continue to have youtube channels. I.e, they didnt blow up and kill them.
I had the luxury of buying a used honda at 1/4 of what they go for new. I can also disassemble and label every part of a snowblower ive never seen before in the time it takes for my friend to go on a beer run. Dont be so dismissive of off brands. People once said the same of just about every brand you know today.
That being said, my calculated governed top speed was 20mph less that ungoverned. The only change to the equation was a difference of 2000 rpm. You can gear a high displacement motor for top end. Its tried and trued, but now imagine instead of 5500 rpm you can go up to 9000.

 

[Bigblockguy]

Sure couldn't afford a V-twin for good ole "SchizoBallz", but I've been researching Predator 420's ($400) and series 40 CVT's for them. Only real hold-back is that current hotrod motor would transfer to next build, "BareBallz".
Already have 6" split rims with 12" tall tires for it, and it's supposed to be a bare minimum cost skeleton sort of wheelie machine, just see how much I can get for how little money. This hotrod motor would make that barely-there lightweight machine terrifying dangerous, and I've promised our Boy Scout troop I'll keep it awhile, let them use it around the church at weekly meetings, and take it on campouts.
Ain't yankin' out nary parts, y'all. Has .020-over ARC rod, crankshaft clearanced for it, .012 ss head gasket, Superman 265 cam, PVL 28 degree flywheel, 22 lb. valve springs, hi-perf coil, .022 low and .036 jets, Walbro fuel pump, master top plate kit,..................etc.
I need a $500 tax-free windfall. Another $140 would put a stock 212 in "BareBallz".

l9000.lol.

Sure couldn't afford a V-twin for good ole "SchizoBallz", but I've been researching Predator 420's ($400) and series 40 CVT's for them. Only real hold-back is that current hotrod motor would transfer to next build, "BareBallz".
Already have 6" split rims with 12" tall tires for it, and it's supposed to be a bare minimum cost skeleton sort of wheelie machine, just see how much I can get for how little money. This hotrod motor would make that barely-there lightweight machine terrifying dangerous, and I've promised our Boy Scout troop I'll keep it awhile, let them use it around the church at weekly meetings, and take it on campouts.
Ain't yankin' out nary parts, y'all. Has .020-over ARC rod, crankshaft clearanced for it, .012 ss head gasket, Superman 265 cam, PVL 28 degree flywheel, 22 lb. valve springs, hi-perf coil, .022 low and .036 jets, Walbro fuel pump, master top plate kit,..................etc.
I need a $500 tax-free windfall. Another $140 would put a stock 212 in "BareBallz".

Thats pretty much where my project started. Bare bones, wanna race my friends, hate to lose so buy a big block and research the best braking systems, then realize that all this might attract attention necessitating cutting across peoples property....
My friends and i agreed to take it to the track. Ill let you know when and where. But i can easily see how you went down the rabbit hole, and i still have a big block in need of a kart.

Yeah a new 670 predator is expensive, but call/ look around locally. The deals are not going to be supplied by harbor freight or
large kart sites.

I built a spicy 674cc kohler command V-twin for less than $220, the motor/block was from a junkyard 2000 series
cub cadet lawn mower. Paid bout $50 for it, pull yourself.

Also 40 series is great for big singles, but not so hot for twins 16hp+. I used a UTV driver+ 1 1/4 belt,
and snowmobile driven for my kart. Cost= $0. 20 year old belt still looks like new.

 

[Functional Artist]

Much to my chagrin however, I've learned that all that power I counted on won't hardly even start to appear until I reach over 4K rpm at least. Currently struggling to make it able to get there.

Don't wait for the power to "show up"

Try an electric powered kart
...PURE POWER right from ZERO RPM's

Check out !ARRIBA!

 

[madprofessor]

Yeah, built motor in my shop, 2nd time for a 212cc mod job. Lots in common with 1st time (it was 12 hp.), but the big difference is the 22 lb. valve springs, didn't do it 1st time, because I was staying cheaper by not changing the stock cast iron flywheel either. They can explode with hand grenade velocity once they get up near 6K rpm., on that "DragginBallz" minibike it could've taken a foot off right through the ankle.
Stock 10.8 lb. valve springs start to float around 5200-5500 rpm, so you can't get them to rev up any higher than that. That's why there was no fear or guilt shipping that death machine up to Ohio, though the guy that bought it's probably still in the hospital anyway. You just shouldn't but 12 hp. and a CVT into something with 6" rims that you can lift off the ground with one hand.
Remember Kawasaki's sales motto circa early '70s? "Put something exciting between your legs............... a Kawasaki."

 

[Millwright]

I'm kind of intrigued with the whole performance upgrade idea. But like I said, I'm a bit skeptical about the longevity with these small 4 cycles turning out crazy RPM.
Once I'm up an running I might remove the governor and get a tachometer and run a maximum peak of 4500. Maybe 5k ?
So much conflicting information a cross all of the you tube builders, especially if you start reading the viewer comments.
Come winter, snow and all, ( not like a comfy Florida winter) I might try some mods just for the experience and pass some time.

 

[madprofessor]

I'll only say one thing about ungoverned Predators..............While you don't hear of many if any connecting rod failures with the governor still functioning (and oil level still correct), if you take the governor out of play the one thing you absolutely should do is get a billet connecting rod. Doesn't have to be an ARC rod like I prefer, and doesn't have to be over stock length.
The portion that I've heard of failing most often is the oil splash arm snapping off from the higher rpm. The ARC rod isn't only a billet piece tested for way more rpm's than you can give it, but the arm is ground to not only splash but to also scoop some oil, great for tossing it up the passages toward the valves. More importantly, it's drilled along its length from the scoop through the rod bearing directly to the crankshaft journal, forcing oil to the most critical point.
Again, doesn't have to be an ARC, just a billet whose arm can take the increased load of centrifugal leverage and the increased oil impact.

 

[Millwright]

Point taken, but I believe that governors are in place for EPA regulations, as well as requlating the speed for typical usages such as generators, power washers etc etc. I don't think that they are there to prevent the engine from self destruction. I'm pretty confident there is a pretty good safety factor above the governed 3600. I'm thinking 4500rpm is comfortable.
Many flywheels are hammered off, or pryed off, or subjected to some grease monkey abuse. So you never know on a used engine what you might be dealing with, but " brand new" I think a flywheel is a pretty stable component beyond 6k.