Building 212 vs 420

[American.Fisher]

I tried searching but I probably didn't have the right keyword/s. I have two larger yard carts that I use to drive around the country on the dirt roads. Right now one has a new 212 that I have put a header, air filter and new jet on. Governor still intact. The other has an 11hp Briggs with carb trouble lol. I can drive them around town here as long as I take backroads. But I'm wanting them to go faster before I take them to town. So, do I continue to build the 212, or would the 420 be a better option? I like the idea of having electric start. But will the big blocks handle higher rpms when modded? Or are they made more for torque? I like the torque but being able to run 50 or so for a long stretch would be nice too. So many options lol. Sorry if this post is confusing lol.

 

[Joe-405]

My bsp 196cc clone will run 50+ at 3/4 throttle with a torque converter. Are you running a regular centrifugal clutch ?

Modding doesn’t help your mph but gearing and clutches or torque converters do for the most part. Your not gaining mph usually unless you pull the governor and pour a lot of cash to run more rpms without grenadine something.

And some pics would be nice.

 

[Clifton]

The bigger engine will have more torque and thus allows you to run a higher gear ratio, so you wont require as high of rpm to go fast.

Bigger engine vs higher revving engine is the question, may be up to personal preference.

 

[bob58o]

High RPM big blocks that will last are expensive to build.

Not sure if it will help, but my next engine will be....

Non-Hemi (Gen III) Predator 212
NR 230 Series Cam (230-0611)
1.3 :1 Stamped Ratio Rockers
22 lb Valve Springs
Billet Flywheel
+0.040" Connecting Rod
Hemi Flat-top Piston
0.009" Head Gasket
Head Milled for 10 :1 Static Compression Ratio
3 angle valve job
Aftermarket slide carb (22mm-24mm)

And a torque converter to give me the low end I want.

 

[ezcome-ezgo]

^^ take this advice. Nobody has put more thought and research into it. Nobody.

 

[KartFab]

a stock big block with have TWICE the torque as a small block. Torque is accelleration. so if you want to have mediocre acceleration and a high top speed, go for the predator 212 that is modified. This is just my 2 cents. I have done both and the price tag is what gets you with any modification.

Here is an example of a pretty crazy cheap mild big block build

honda gx340/390 or predator 420
high flow intake
high flow exhaust
rejet
stop right here and you are at 18 HP and the cost of the block plus $100 you can gear for 40 mph with a 40 series torque converter where you coudl only gear for 28 mph with a small block.

If you want to go further, get a set of champion 1.1:1 ratio rockers, and a knock off 34mm roundslide carburetor, a billet connecting rod, hd single rate springs, advance timing 4 degrees, and get an NR racing 280 cam, marine grind. This will top out at 5500 rpm, but give you insane torque and still be able to use the torque converter. You will top out at 55-60 mph easily and you will get there super, super fast.

Just an option to consider. Torque is acceleration, gearing is top speed. Id hate for you to acheive your top speed but only be disappointed on how slowly it got there and how many belts you chewed up or clutches you burned up trying to get there with a bad gear ratio.

A mini bike build im working on has the following, i dont reccomend doing this but its going to be fun.

Predator 212 block
1.3 black venom rockers
honda gx160 UT2 head: 27/24 ported head milled .030" 3 angle valve job (15.7cc)
fire ring head gasket
2.815" forged wiseco piston, 3 ring
wiseco connecting rod
billet lifters
cut to length pushrods
NR racing 280-0611 cam (rpm grind)
stock balanced crank
36 lb single rate springs
12:1 compression ratio
24mm mikuni flat slide carburetor with 140 main and 20 pilot
K&N air filter with pre-filter
.011 top ring end gap
.014" 2nd ring end gap
Timing set at 28-32 DBTDC

 

[American.Fisher]

I tried to get everyone, sorry for the long post lol.

My bsp 196cc clone will run 50+ at 3/4 throttle with a torque converter. Are you running a regular centrifugal clutch ?

Modding doesn’t help your mph but gearing and clutches or torque converters do for the most part. Your not gaining mph usually unless you pull the governor and pour a lot of cash to run more rpms without grenadine something.

And some pics would be nice.

The cart has an older 30 series TC on it from what I can tell. I will go take some pictures and get them uploaded and may have a few gear questions once I have them uploaded.

The bigger engine will have more torque and thus allows you to run a higher gear ratio, so you wont require as high of rpm to go fast.

Bigger engine vs higher revving engine is the question, may be up to personal preference.

I appreciate that info! I will take that into consideration.

High RPM big blocks that will last are expensive to build.

Not sure if it will help, but my next engine will be....

Non-Hemi (Gen III) Predator 212
NR 230 Series Cam (230-0611)
1.3 :1 Stamped Ratio Rockers
22 lb Valve Springs
Billet Flywheel
+0.040" Connecting Rod
Hemi Flat-top Piston
0.009" Head Gasket
Head Milled for 10 :1 Static Compression Ratio
3 angle valve job
Aftermarket slide carb (22mm-24mm)

And a torque converter to give me the low end I want.

That sounds like quite the well thought out build! Thank you!

a stock big block with have TWICE the torque as a small block. Torque is accelleration. so if you want to have mediocre acceleration and a high top speed, go for the predator 212 that is modified. This is just my 2 cents. I have done both and the price tag is what gets you with any modification.

Here is an example of a pretty crazy cheap mild big block build

honda gx340/390 or predator 420
high flow intake
high flow exhaust
rejet
stop right here and you are at 18 HP and the cost of the block plus $100 you can gear for 40 mph with a 40 series torque converter where you coudl only gear for 28 mph with a small block.

If you want to go further, get a set of champion 1.1:1 ratio rockers, and a knock off 34mm roundslide carburetor, a billet connecting rod, hd single rate springs, advance timing 4 degrees, and get an NR racing 280 cam, marine grind. This will top out at 5500 rpm, but give you insane torque and still be able to use the torque converter. You will top out at 55-60 mph easily and you will get there super, super fast.

Just an option to consider. Torque is acceleration, gearing is top speed. Id hate for you to acheive your top speed but only be disappointed on how slowly it got there and how many belts you chewed up or clutches you burned up trying to get there with a bad gear ratio.

A mini bike build im working on has the following, i dont reccomend doing this but its going to be fun.

Predator 212 block
1.3 black venom rockers
honda gx160 UT2 head: 27/24 ported head milled .030" 3 angle valve job (15.7cc)
fire ring head gasket
2.815" forged wiseco piston, 3 ring
wiseco connecting rod
billet lifters
cut to length pushrods
NR racing 280-0611 cam (rpm grind)
stock balanced crank
36 lb single rate springs
12:1 compression ratio
24mm mikuni flat slide carburetor with 140 main and 20 pilot
K&N air filter with pre-filter
.011 top ring end gap
.014" 2nd ring end gap
Timing set at 28-32 DBTDC

I appreciate that information also. That will give me something to chew on. May be a silly question, but once the proper upgrades are completed, new flywheel, etc, how safe is it to run wide open throttle or close to it for an extended period? Example, riding to town and back on the backroads.

Thanks everyone! I am going to get some pics then I may have a few more questions.

 

[American.Fisher]

Okay, here are the pictures of what I am working with. It's kind of a bigger cart, 18" wheels so that's why I was wondering if the 420 would be a better option for me to build.

 

[American.Fisher]

I don't have much clearance at the sprocket as you can tell. Wouldn't I need a bigger sprocket? Or smaller sprocket? And is there any way to check the size of the sprocket that is attached to the (and my brain just went blank, the rod connecting the TC to the chain). Wow. Total blank moment. Thanks yall.

---------- Post added at 06:18 PM ---------- Previous post was at 06:05 PM ----------

Holy molys. I just seen the price of the 40 series TC too. Wow! And it says only good up to 18hp...so what does everyone do, just burn up belts? Any cheaper options as far as the TC goes?

 

[bob58o]

The intermediate shaft is called a jackshaft.
What size is it? 5/8", 3/4", 7/8" ...?

You can just count the teeth on the sprocket. The chain will either have 3/8" or 1/2" pitch.
3/8" pitch will be #35 chain. 1/2" pitch will be #40, #41, or #420 chain.

 

[bob58o]

Lets say you rock the 420cc with a 40 series TC...
40c (driver) with 40d (driven) gives 1 :1 final ratio and 2.43 :1 when the TC engages.

If you have a 5 :1 sprocket ratio (60T big sprocket, 12T little sprocket)....

When the TC engages, you have 5 x 2.43 = 12.15 :1 Gear Ratio
Which roughly translates 238 lbs of linear force pushing the kart at engagement.
(belt systems generally eat up 20% of the available TQ)

When it shifts out, you have 5 x 1.00 = 5.0 :1 Gear Ratio.
At 4500 RPM, with 18" tires... you'll be traveling 48 mph

For comparison, a 212 with 30 series TC and 7" driven pulley with 5 :1 sprocket ratio....
135 lbs linear force at engagement.

212 with 30 series TC and 6" driven pulley with 5 :1 sprocket ratio...
116 lbs linear force at engagement.

Those last examples are not great gear ratios. A 212 with 30 series TC and 18" Tires probably needs closer to 7.5 :1 sprocket ratio, not 5.0 :1 sprocket ratio.
With a 7.5 : 1 sprocket ratio and 30 series TC with 6" driven pulley, you need to turn about 6500 RPM to go 50 MPH, might not get there. 50 mph on a larger kart with a 212 is not an easy feat.
With a 7.5 :1 sprocket ratio and 30 series TC with 7" driven pulley you'll need to turn about 7500 RPM to go 50 MPH, again - might not get there.

http://kartingdistributors.com/pdfs/30series.pdf
https://www.bmikarts.com/PDF/Comet_40series.pdf

---------- Post added at 10:25 PM ---------- Previous post was at 10:08 PM ----------

I used a 3/4" jackshaft and purchased this TC. The proper belt is determined by the crankshaft to jackshaft spacing.
https://www.amazon.com/Yoscam-Torque-Converter-Driven-Driver/dp/B010N3CG00

Even cheaper...
https://www.amazon.com/CNCShop-Torq...i=B019SL0LUK&refRID=N6JTBHBY3YBNEFKW8BFX&th=1

 

[American.Fisher]

The intermediate shaft is called a jackshaft.
What size is it? 5/8", 3/4", 7/8" ...?

You can just count the teeth on the sprocket. The chain will either have 3/8" or 1/2" pitch.
3/8" pitch will be #35 chain. 1/2" pitch will be #40, #41, or #420 chain.

Thanks for the time and the information! From what I can tell, measuring across the end of the threads on the jackshaft it is 3/4". But all of the other 3/4" JS's that I am seeing are not threaded. Is it because of this is an older style? The sprocket has 10 teeth on it currently. I forgot to measure for the pitch however and now its pouring down rain and the wife is wanting to go eat lol so I'll have to do that maybe when I get back.

Lets say you rock the 420cc with a 40 series TC...
40c (driver) with 40d (driven) gives 1 :1 final ratio and 2.43 :1 when the TC engages.

If you have a 5 :1 sprocket ratio (60T big sprocket, 12T little sprocket)....

When the TC engages, you have 5 x 2.43 = 12.15 :1 Gear Ratio
Which roughly translates 238 lbs of linear force pushing the kart at engagement.
(belt systems generally eat up 20% of the available TQ)

When it shifts out, you have 5 x 1.00 = 5.0 :1 Gear Ratio.
At 4500 RPM, with 18" tires... you'll be traveling 48 mph

For comparison, a 212 with 30 series TC and 7" driven pulley with 5 :1 sprocket ratio....
135 lbs linear force at engagement.

212 with 30 series TC and 6" driven pulley with 5 :1 sprocket ratio...
116 lbs linear force at engagement.

Those last examples are not great gear ratios. A 212 with 30 series TC and 18" Tires probably needs closer to 7.5 :1 sprocket ratio, not 5.0 :1 sprocket ratio.
With a 7.5 : 1 sprocket ratio and 30 series TC with 6" driven pulley, you need to turn about 6500 RPM to go 50 MPH, might not get there. 50 mph on a larger kart with a 212 is not an easy feat.
With a 7.5 :1 sprocket ratio and 30 series TC with 7" driven pulley you'll need to turn about 7500 RPM to go 50 MPH, again - might not get there.

http://kartingdistributors.com/pdfs/30series.pdf
https://www.bmikarts.com/PDF/Comet_40series.pdf

---------- Post added at 10:25 PM ---------- Previous post was at 10:08 PM ----------

I used a 3/4" jackshaft and purchased this TC. The proper belt is determined by the crankshaft to jackshaft spacing.
https://www.amazon.com/Yoscam-Torque-Converter-Driven-Driver/dp/B010N3CG00

Even cheaper...
https://www.amazon.com/CNCShop-Torq...i=B019SL0LUK&refRID=N6JTBHBY3YBNEFKW8BFX&th=1

Thanks for those links and the information. Sounds like for this bigger kart if I want to go anywhere at a decent speed I am going to need the 420 lol.The electric start and the ability to run some lights at night will be an added bonus as well.

 

[Joe-405]

The less modded 420cc will be more reliable also.