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Posted: 2/14/2024 3:51:39 PM EDT
I bought this here mini bike around a year ago. Put a gokart 212cc motor in it. I had a lot of fun with it this last year but always kinda wanted a little more out of the engine. Threw a cam, billet rod, billet flywheel, and some valve springs at it. Noticeable gains

Currently does 50 which is scooting pretty good

But Im not sure I can leave good enough alone

Harbor freight has the 420cc engine which from research will fit my frame. Albeit Ill have to do some modifying and pull out the CVT and replace with a bigger heavier. Itll be a good little bit of work with fitting and welding. Im sure eventually Id want to throw the go fast parts at this engine as well.

The weight difference is quite a bit though. The 212cc is ~36 pounds. the 420cc coming in at a bit under 80 pounds. Id be surprised if the frame and tires weigh 80 pounds

Is the juice gunna be worth the squeeze? Double the CCs double the fun? Double the weight and no fun?

ETA Now looking at amazon ATV/Dirt bike motors



Link Posted: 2/14/2024 3:57:59 PM EDT
[#1]
Why don't you just buy a Honda monkey or similar?

Or a KX100 to mod in to a mini super moto?

Mini bikes are for poor people, and here you are dumping real money in to one.

You should buy a die grinder and try you hand at porting the cylinder head you have currently. That's some proper hop up work.
Link Posted: 2/14/2024 4:03:43 PM EDT
[#2]
Holy hell, 50 on that thing?  That's crazy....
Link Posted: 2/14/2024 4:03:49 PM EDT
[#3]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
Why don't you just buy a Honda monkey or similar?

Or a KX100 to mod in to a mini super moto?

Mini bikes are for poor people, and here you are dumping real money in to one.

You should buy a die grinder and try you hand at porting the cylinder head you have currently. That's some proper hop up work.
View Quote


I have considered it

But thats quite a bit more money when this guy is sitting in the garage. Even throwing a bigger motor at it with the go fast parts isnt going to approach a used dirt bike cost

I mostly just like dicking around in the river bottoms and rural roads with it

I also kinda just like to tinker
Link Posted: 2/14/2024 4:04:54 PM EDT
[#4]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
Holy hell, 50 on that thing?  That's crazy....
View Quote


Sometimes in the darkness too

Link Posted: 2/14/2024 4:05:02 PM EDT
[#5]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
Why don't you just buy a Honda monkey or similar?

Or a KX100 to mod in to a mini super moto?

Mini bikes are for poor people, and here you are dumping real money in to one.

You should buy a die grinder and try you hand at porting the cylinder head you have currently. That's some proper hop up work.
View Quote


Yes. Port the intake and exhaust. Dome the top of the piston, drop the top stroke gap, start advancing the timing for more torque. Get a smoother breathing muffler. Turbo the crank. Weight the crank for a full circle crankshaft, supercharge the intake, convert it to nitromethane. Bore it out. Come on now get this bitch running like a formula one dragster. Do you or do you not want to see 200hp?
Link Posted: 2/14/2024 4:12:16 PM EDT
[#6]
Same frame with a 420cc swap

420cc Mega Moto First Ride ~ Too Much Torque!!!!
Link Posted: 2/14/2024 4:23:01 PM EDT
[#7]
I never dicked around with mini bikes but I did a sprocket swap on a Trail 70 I had. It was a blast maxing out the speedometer.  I could do about 45 on it.  Later I swapped out the 70cc 3 speed auto for a 110cc 4 speed manual out of a honda pit bike that got wrecked.  I could do 72mph according to gps after another sprocket swap. At that speed it was goofy levels of squirrelyness though.  Yes i just invented the word squirrelyness.

OP do you really want to go faster then 50 on that thing with basically no meaningful suspension?  I know the tires kind of act like suspension but it's not the same thing as a real dampened suspension.  I see it has a basic spring front forks.  That's better then nothing but still..     Also at those speeds you really should consider getting the tires balanced. Those big balloon tires can be really out of balance.  Even my trail 70 would shake violently when I revved it up in top gear while holding the rear tire off the ground before I got it balanced.

I guess if you end up doing it, post back with the results. And btw you need a gun rack on that thing. LoL Have you learned nothing from GD?!?!?!
Link Posted: 2/14/2024 4:24:32 PM EDT
[#8]
Discussion ForumsJump to Quoted PostQuote History
Quoted:


I have considered it

But thats quite a bit more money when this guy is sitting in the garage. Even throwing a bigger motor at it with the go fast parts isnt going to approach a used dirt bike cost

I mostly just like dicking around in the river bottoms and rural roads with it

I also kinda just like to tinker
View Quote

Used Groms are cheap, and the plus side is you (probably) won't get another ticket because it's street legal.

As for the engine swap, I thought you had a pretty decked out 212 in there. With the 420cc 'only' making an advertised 13hp you may not get the extra power benefit to outweigh the extra weight added.
Link Posted: 2/14/2024 4:26:06 PM EDT
[#9]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
I never dicked around with mini bikes but I did a sprocket swap on a Trail 70 I had. It was a blast maxing out the speedometer.  I could do about 45 on it.  Later I swapped out the 70cc 3 speed auto for a 110cc 4 speed manual out of a honda pit bike that got wrecked.  I could do 72mph according to gps after another sprocket swap. At that speed it was goofy levels of squirrelyness though.  Yes i just invented the word squirrelyness.

OP do you really want to go faster then 50 on that thing with basically no meaningful suspension?  I know the tires kind of act like suspension but it's not the same thing as a real dampened suspension.  I see it has a basic spring front forks.  That's better then nothing but still..     Also at those speeds you really should consider getting the tires balanced. Those big balloon tires can be really out of balance.  Even my trail 70 would shake violently when I revved it up in top gear while holding the rear tire off the ground before I got it balanced.

I guess if you end up doing it, post back with the results. And btw you need a gun rack on that thing. LoL Have you learned nothing from GD?!?!?!
View Quote


I dont want to go that much faster

But I would like to be able to cruise 50-60 or so

I mostly just want ear splitting grins from stopped to 60mph or so

It sounding angrier would be kinda cool too
Link Posted: 2/14/2024 4:27:41 PM EDT
[#10]
Discussion ForumsJump to Quoted PostQuote History
Quoted:

Used Groms are cheap, and the plus side is you (probably) won't get another ticket because it's street legal.

As for the engine swap, I thought you had a pretty decked out 212 in there. With the 420cc 'only' making an advertised 13hp you may not get the extra power benefit to outweigh the extra weight added.
View Quote


That last part is somewhat my worry

However Im not scared to throw the go fast parts at this engine either and likely will so if I go that route
Link Posted: 2/14/2024 4:32:38 PM EDT
[#11]
I had a monster moto that I put the Predator 212 on.  It would get up to mid 40's MPH on a flat surface based on one of those GPS phone app speedos.  The problem however is that the brakes weren't good enough to stop it and would have had to be upgrade significantly.  I can't imagine going 50-60mph on one of those thing with no suspension and sketchy brakes.
Link Posted: 2/14/2024 5:13:25 PM EDT
[#12]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
I had a monster moto that I put the Predator 212 on.  It would get up to mid 40's MPH on a flat surface based on one of those GPS phone app speedos.  The problem however is that the brakes weren't good enough to stop it and would have had to be upgrade significantly.  I can't imagine going 50-60mph on one of those thing with no suspension and sketchy brakes.
View Quote


Ya this ones a bit bigger and has front suspension and front and rear disc brakes
Link Posted: 2/14/2024 5:16:08 PM EDT
[#13]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
OP do you really want to go faster then 50 on that thing with basically no meaningful suspension?  I know the tires kind of act like suspension but it's not the same thing as a real dampened suspension.  I see it has a basic spring front forks.  That's better then nothing but still..     Also at those speeds you really should consider getting the tires balanced. Those big balloon tires can be really out of balance.  Even my trail 70 would shake violently when I revved it up in top gear while holding the rear tire off the ground before I got it balanced.
View Quote


I vote "No". The forks aren't designed for those loads... there's a reason those bikes have weight limits and limited top speeds.  I really wouldn't want to break a fork at high speed - or any speed, for that matter.
Link Posted: 2/14/2024 5:23:16 PM EDT
[#14]
Throw a bag of concrete on your lap and take a spin and see how if effects your speeds.
Link Posted: 2/14/2024 5:29:05 PM EDT
[#15]
Gotta watch the speed ratings on the tires too- like the guys putting motors on mountain bikes and cruisers, overheating tires and wiping out.  

<--- Has one of the camo models sitting the back yard I bought to take to the farm but a friend wants it and is willing to pay more than I paid for it.
Link Posted: 2/14/2024 5:30:13 PM EDT
[#16]
I got a couple of old go carts from my brother in laws race shop. He had them since he was young and he told me to come get them. I want to toss something wild in one of them.

I also want to get a pit bike or something. My 250 ktm pro bike is just too freaking big and loud for just around my propety.

Attachment Attached File
Link Posted: 2/14/2024 5:43:04 PM EDT
[#17]
I wouldn't do a big block swap them engines are huge and the cvt makes it even bigger. All your power is in the head and cam go to childishconcepts.com and consult with him on what your wanting to do  and he'll build you a head to get you some good power. If you want all topend the black mamba sr cam is a great choice as is a 308 dyno cam theres a ton of good cams. You can get get big block power without all the weight.
Eta. I have the exact same frame I had a 236 that was built for bottom end with low gearing I was around 55
Link Posted: 2/14/2024 5:43:19 PM EDT
[#18]
I really want to make an electric cross cart or caged E go cart. I have a nice big park across the street, with a bunch of trails. It would be fun as heck under night vision but would need to be quiet like a ev.

Added bonus is a shtf vehicle I could recharge from solar.
Link Posted: 2/14/2024 5:44:26 PM EDT
[#19]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
I wouldn't do a big block swap them engines are huge and the cvt makes it even bigger. All your power is in the head and cam go to childishconcepts.com and consult with him on what your wanting to do  and he'll build you a head to get you some good power. If you want all topend the black mamba sr cam is a great choice as is a 308 dyno cam theres a ton of good cams. You can get get big block power without all the weight.
View Quote


I got a hot 265 cam in it

But yeah maybe a bigger carb and cam might do the trick
Link Posted: 2/19/2024 2:40:50 PM EDT
[#20]
Im still thinking about throwing the 420 at it
Link Posted: 2/19/2024 4:23:20 PM EDT
[#21]
You should buy a spare head for what you have and practice porting it. That would be super cool.
Link Posted: 2/21/2024 12:03:22 PM EDT
[#22]
They do have china motors for 300 bucks or so. 250CC with a manual trans

Wonder how hard that would be to make work

14HP, 5 gears, and supposedly will turn 7500 RPMs

Hmm

Link Posted: 2/21/2024 12:15:33 PM EDT
[#23]
Is that a titty bar you're parked in front of?
Link Posted: 2/21/2024 12:17:03 PM EDT
[#24]
I have that minibike with the 212. I have nothing to offer other than studded tires on a frozen lake is awesome for all ages.
Link Posted: 2/21/2024 12:17:46 PM EDT
[#25]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
Is that a titty bar you're parked in front of?
View Quote


That building has had many lives.

At one point it sure was a titty bar

Most recently it was the Grim Reapers club house until they got raided by the feds lol
Link Posted: 2/21/2024 12:26:17 PM EDT
[#26]
If you end up doing it be sure to post pics and specs.
Link Posted: 2/21/2024 12:30:32 PM EDT
[#27]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
If you end up doing it be sure to post pics and specs.
View Quote


Kinda thinking about the chinese motors with the transmission. I think the trans would really change the way this thing feels

Way cheaper and has 14HP which is the base hp of the 420s

Supposedly will turn 7500 RPMs too
Link Posted: 2/21/2024 12:36:44 PM EDT
[#28]
Is that street legal?
Link Posted: 2/21/2024 12:38:28 PM EDT
[#29]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
Is that street legal?
View Quote


Nope


Link Posted: 2/21/2024 12:39:35 PM EDT
[#30]
So how'd that go?
Link Posted: 2/21/2024 12:40:34 PM EDT
[#31]
Will you be able to stop it or is that an afterthought?
Link Posted: 2/21/2024 12:45:09 PM EDT
[#32]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
So how'd that go?
View Quote


Not too bad

Just a warning

But I dont really hit the streets with it too much anymore

Use it alot in the backroads and river bottoms sorta thing

Just kinda fun to scoot around since theres a ton of river bottom areas around

Still feel I want a little more though. Probably should just buy a real bike. But I dont really want to spend that sorta monies and the family HATES motorcycles

The mini falls into some weird loophole for them though
Link Posted: 2/21/2024 12:46:00 PM EDT
[#33]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
Will you be able to stop it or is that an afterthought?
View Quote


Its got hyd disc brakes front and rear

It stops pretty good as is
Link Posted: 2/21/2024 12:56:16 PM EDT
[#34]
I've got two pickled Animal engines from when I raced.
You wouldn't mind 7000 RPM on alcohol, would you?
I'll throw in the pipes, air filter, and a set of jets.
That should get you to the Emergency Room pretty quick.  
Link Posted: 2/21/2024 1:02:35 PM EDT
[#35]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
They do have china motors for 300 bucks or so. 250CC with a manual trans

Wonder how hard that would be to make work

14HP, 5 gears, and supposedly will turn 7500 RPMs

Hmm

https://m.media-amazon.com/images/W/MEDIAX_849526-T1/images/I/71nLldLg0cL._AC_SX679_.jpg
View Quote

I have one of those 229cc (they're not 250cc) CG motors in a chinese dirt bike that's making about 20bhp and revs to 9500rpm. Basically the exhaust ports and systems are garbage, but you can easily improve them and the motors respond really well to this. Then I skimmed the head raising the CR to 9.5:1 , added 4 degrees of advance to timing and put in a 290degree cam. The stock VM26 carb was good enough, but now it runs massive jets and a pod style filter
Link Posted: 2/21/2024 1:11:53 PM EDT
[#36]
Discussion ForumsJump to Quoted PostQuote History
Quoted:

I have one of those 229cc (they're not 250cc) CG motors in a chinese dirt bike that's making about 20bhp and revs to 9500rpm. Basically the exhaust ports and systems are garbage, but you can easily improve them and the motors respond really well to this. Then I skimmed the head raising the CR to 9.5:1 , added 4 degrees of advance to timing and put in a 290degree cam. The stock VM26 carb was good enough, but now it runs massive jets and a pod style filter
View Quote


No shit?

Where's a guy look at aftermarket parts for this kinda engine?

What chain does the sprocket that comes with it take? I can't seem to find that info off hand
Link Posted: 2/21/2024 1:22:10 PM EDT
[#37]
I was going to ask about just swapping an actual motorcycle engine  in but I see you’re there. In for the adventure. You surpassed the safety limit on that setup long ago
Link Posted: 2/21/2024 1:24:05 PM EDT
[#38]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
I really want to make an electric cross cart or caged E go cart. I have a nice big park across the street, with a bunch of trails. It would be fun as heck under night vision but would need to be quiet like a ev.

Added bonus is a shtf vehicle I could recharge from solar.
View Quote

If I had time and money I think I’d put together an E-bike similar to a Honda Monkey. I’ve even thought about how cool a hybrid setup would be. I’d want something from scratch because I’m too big for the mini bikes.
Link Posted: 2/21/2024 1:28:17 PM EDT
[#39]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
I was going to ask about just swapping an actual motorcycle engine  in but I see you’re there. In for the adventure. You surpassed the safety limit on that setup long ago
View Quote


Lol ya if I engine swap I'm gunna give a good look at structural welds and retorqueing nuts here and there
Link Posted: 2/21/2024 1:40:38 PM EDT
[#40]
Discussion ForumsJump to Quoted PostQuote History
Quoted:


Not too bad

Just a warning

But I dont really hit the streets with it too much anymore

Use it alot in the backroads and river bottoms sorta thing

Just kinda fun to scoot around since theres a ton of river bottom areas around

Still feel I want a little more though. Probably should just buy a real bike. But I dont really want to spend that sorta monies and the family HATES motorcycles

The mini falls into some weird loophole for them though
View Quote View All Quotes
View All Quotes
Discussion ForumsJump to Quoted PostQuote History
Quoted:
Quoted:
So how'd that go?


Not too bad

Just a warning

But I dont really hit the streets with it too much anymore

Use it alot in the backroads and river bottoms sorta thing

Just kinda fun to scoot around since theres a ton of river bottom areas around

Still feel I want a little more though. Probably should just buy a real bike. But I dont really want to spend that sorta monies and the family HATES motorcycles

The mini falls into some weird loophole for them though


I'm asking because I'm wondering about picking one up for the snowmobile trails around here.
Link Posted: 2/21/2024 1:46:03 PM EDT
[#41]
Discussion ForumsJump to Quoted PostQuote History
Quoted:


I'm asking because I'm wondering about picking one up for the snowmobile trails around here.
View Quote


I think its fun and easy to trek around.

I don't find it that small. It's a bigger mini bike. However I am 5'6".

This frame is a mega moto 212

Depending on how anal your state is you could very well get them street legal. Main problem for me is title in my state. I could maybe go about getting it street legal here but it sounds like more work than it's worth for as little as I ride it on the streets. But every state be different

I think its been awesome for dirt/rock/offroading in the bottoms

Link Posted: 2/21/2024 1:59:03 PM EDT
[#42]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
I got a couple of old go carts from my brother in laws race shop. He had them since he was young and he told me to come get them. I want to toss something wild in one of them.
View Quote


If my memory isn't off, Amazon has Chinese copies of Honda ATC engines for a few hundred bucks.  250cc, electric start, manual clutch, four forward gears and one reverse.
Link Posted: 2/21/2024 2:13:02 PM EDT
[#43]
I think this 200/250 amazonia motor is gunna be my move

Its cheap. I mean 300 bucks it can blow up after a few months and I wont even feel that bad

All in one. I dont have to worry about upgrading a CVT when Im getting an actual transmission. Finally no more 6000 RPMs road cruising lol

Got as much or more power than the base big 420 motor I was thinking about. As pointed out above an electric start too which would be neat

About the only thing I gotta figure out is the chain to the rear tire which cant be that hard. Engine looks like its running the chain off the left side. My bike currently has the sprocket on the right.
Link Posted: 2/21/2024 2:27:44 PM EDT
[#44]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
I think this 200/250 amazonia motor is gunna be my move

Its cheap. I mean 300 bucks it can blow up after a few months and I wont even feel that bad

All in one. I dont have to worry about upgrading a CVT when Im getting an actual transmission. Finally no more 6000 RPMs road cruising lol

Got as much or more power than the base big 420 motor I was thinking about. As pointed out above an electric start too which would be neat

About the only thing I gotta figure out is the chain to the rear tire which cant be that hard. Engine looks like its running the chain off the left side. My bike currently has the sprocket on the right.
View Quote


The Heald Super Bronc adult minibikes (or at least some of them) used a jackshaft mounted just aft of the engine, due to the engine output shaft being on the left and the rear wheel sprocket being on the right.

ETA:
Attachment Attached File


ETA2: And after looking again, I see that is your current configuration.
Link Posted: 2/21/2024 2:35:42 PM EDT
[#45]
Discussion ForumsJump to Quoted PostQuote History
Quoted:


The Heald Super Bronc adult minibikes (or at least some of them) used a jackshaft mounted just aft of the engine, due to the engine output shaft being on the left and the rear wheel sprocket being on the right.

ETA:
https://www.ar15.com/media/mediaFiles/64025/HealdSB_jpg-3136528.JPG

ETA2: And after looking again, I see that is your current configuration.
View Quote


Yep correct. Maybe I could get the jackshaft to work as is. That would simplify things

It does mount completely different though now that I really look at it.

Its mounting on the front and rear where as these mini bike engines mount to the bottom

Surely that cant be too hard to rig out though. I do have a welder
Link Posted: 2/21/2024 2:43:42 PM EDT
[#46]
Discussion ForumsJump to Quoted PostQuote History
Quoted:


Yep correct. So I can chop that out and be good to go and have a bit more room.

It does mount completely different though now that I really look at it.

Its mounting on the front and rear where as these mini bike engines mount to the bottom

Surely that cant be too hard to rig out though. I do have a welder
View Quote View All Quotes
View All Quotes
Discussion ForumsJump to Quoted PostQuote History
Quoted:
Quoted:


The Heald Super Bronc adult minibikes (or at least some of them) used a jackshaft mounted just aft of the engine, due to the engine output shaft being on the left and the rear wheel sprocket being on the right.

ETA:
https://www.ar15.com/media/mediaFiles/64025/HealdSB_jpg-3136528.JPG

ETA2: And after looking again, I see that is your current configuration.


Yep correct. So I can chop that out and be good to go and have a bit more room.

It does mount completely different though now that I really look at it.

Its mounting on the front and rear where as these mini bike engines mount to the bottom

Surely that cant be too hard to rig out though. I do have a welder


As I recall, those engines usually slip in between tabs on the motorcycle or atc frame, with bolts running through from the side and nuts on the opposite side.  Mock up a couple plates to fit on either side of the engine using cardboard, then transfer the design to steel plate (I would guess 3/16 inch thickness is probably enough, if the plates aren't too 'skeletonized'), cut it out, then weld or bolt it to the frame.  If you don't have to notch or remove the frame's original mounting plate, it can serve as a skid plate for the new engine.

ETA: The plates could also serve as mounting points for the jackshaft bearings, if you need new mounting points for those.
Link Posted: 2/21/2024 2:48:23 PM EDT
[#47]
I think this makes most sense to try and do

Just enough trouble to make it fun

I just hope the end result is what Im thinking it will be in my head

Would be sorta lame to get all done and it still have the exact same performance
Link Posted: 2/21/2024 2:54:55 PM EDT
[#48]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
I think this makes most sense to try and do

Just enough trouble to make it fun

I just hope the end result is what Im thinking it will be in my head

Would be sorta lame to get all done and it still have the exact same performance
View Quote


Just going from a CVT to a four or five speed manual is going to make a big difference.  Should also be a wider rpm range on the new engine, since the new engine is designed for road use, instead of use on generators, tillers...
Link Posted: 2/21/2024 2:58:04 PM EDT
[#49]
Discussion ForumsJump to Quoted PostQuote History
Quoted:


Just going from a CVT to a four or five speed manual is going to make a big difference.  Should also be a wider rpm range on the new engine, since the new engine is designed for road use, instead of use on generators, tillers...
View Quote


After looking a bit closer it does look to have bottom bolt holes too

I guess stay tuned

Im gunna sit on the thought for a few days and then maybe make a move
Link Posted: 2/21/2024 3:03:51 PM EDT
[#50]
When you start designing your mount for the engine, keep in mind that the engine you are installing may have been intended to be dropped down from the frame when it is removed for teardown, while your frame is designed for an engine that slides out the side for removal.  That may require your mount be bolted the frame (or bolted to tabs welded to the frame) so that at least one side of the mount can be removed to allow sliding the engine out of the frame to the side.
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