r/minibikes Sep 26 '25

Other AI posts, yes or no?

6 Upvotes

Been getting a few AI posts, so we want to try to get ahead of this before it becomes an issue. Let's vote on it, and we'll make a rule accordingly.

20 votes, Oct 03 '25
11 No
0 Yes
9 Within Reason (inspiration only)

r/minibikes May 19 '21

Governors, Flywheels, And An Internet Full Of Crap

129 Upvotes

Taken from this thread.

"This has come up recently, again, so I'm going to post this here. What you are about to read is a couple of articles I wrote sometime back, that address the function of the governor, the exploding flywheel MYTH, and all the crap to go with it. What I have written in based on years of personal experience (not "I heard, read, or was told" as well as extensive research and others' personal experience. It was originally written for the go kart crowd, but the same information applies to all similarly-derived small engines. Take it for what it's worth and insert your favourite fine print here, but I'm telling you- there is so much MIS-information out there, it's disgusting. Grab your favourite beverage, smoke if ya got 'em, and read on...

It is absolutely amazing how often we run into this here- and how often we find ourselves banging away on the keyboard, typing out the same old answers. So, I felt it was a good idea to write up a little blurb on the topic- If requested, I'll sticky it- to hopefully save us all some future work. Let's start by outlining the governor's job description. Everyone knows that the governor tries to limit engine speed to (usually) 3600 RPM. But wait- there's more. The reality of it is this- the governor's job is to try to MAINTAIN 3600, not just limit it. The governor reacts to changing loads on the engine- decreasing throttle if it starts to run too fast, and INCREASING throttle if it starts to bog. This is why it is called a "governor", and not simply a "rev limiter".

Now- On to the question: "If I take out my governor, is the flywheel gonna go off like an atom bomb, blowing semi-molten schmutz everywhere, and killing every living thing in a 15-block radius?"

The short answer is no. The long answer: There are many factors involved here, and each must be carefully considered.

1) I always advise people that IF they are going to run well above governed RPM, to do it by fully removing the governor's internal mechanisms, and NOT simply bypassing it externally. Many governors are designed in such a way that if over-revved, can suffer component interference inside the crankcase, and/or have internal parts forced right off the shaft and bounce around loose inside the crankcase. Either case can cause severe engine damage. NOT an "explosion", just largely F'd up internals.

2) IF you are going to run ungoverned with an otherwise stock engine, keep the factory spec valvesprings in place. At a high enough RPM, weaker springs will cause a condition known as "valve float" or "valve flutter". This occurs when the valves cannot slam closed fast enough before the next cycle. This cause compression losses, and as a result, prevents the engine from spinning faster than that point. Valve flutter tends to occur in our engines around 5000-5500RPM. Your results will vary, based on your individual engine, spring condition, etc. Valve flutter occurs at a lower RPM than it would normally take to cause a flywheel mishap.

3) IF you want to get into RPM ranges HIGHER than this (say 5500+), now is the time to go shopping for high-performance internals. A billet aluminum flywheel, connecting rod, and stiffer valve springs are what's called for. Stiffer springs allow the valves to react faster, so at higher RPM, the valves won't float- NOW things really do have the potential to get a little crazy, so it's time to reach into your pockets for better quality parts.

4) Your connecting rod is MUCH more likely to fail than your flywheel. I have witnessed MANY more conrod failures than flywheel failures. In fact, I have never seen a flywheel failure. Most here haven't.

5) Contrary to popular belief, a flywheel is NOT going to vapourize at 3601 RPM. This is NOT why your engine is governed to 3600 RPM. Your engine is governed to 3600 RPM because it is an industry-standard operating speed for all the implements these engines are designed to power. Let's NOT lose sight of the fact that these are industrial stationary engines- made and marketed with the primary purpose of powering equipment. Generators, pumps, power washers, welders, cement mixers, tillers, trenchers, tampers- you name it- and the implement are designed to run at 3600 RPM- So the engines are factory set to 3600 RPM. It's that simple. When a flywheel is manufactured, it is designed to run well above normal operating speed. It's called a safety margin.

6) NOTHING is 100% guaranteed. You can do everything completely properly, and have a flywheel fail at a "normal speed". OR, you can do everything wrong, and run the he// out of the engine at 7500 RPM on a stock 'wheel for a lifetime and never have a problem. Sometimes, there's just no accounting for "Spit Happens". Write that down.

7) IF you are running an otherwise stock, ungoverned engine, is it adviseable to avoid excessively free-revving the engine. Use proper gear ratios to keep a bit of a load on the engine at full speed, wide open throttle. Don't try to rev the wee out of the engine with the clutch, chain, or belt off. A load on the engine helps keep harmful vibrations (harmonics) in check. If you have an insanely long, steep downhill stretch in your riding route, back off the throttle going down it. If you hear the valves floating or the engine starting to over-rev, apply some brake force. Coasting too fast can force the engine to spin even faster than valve flutter can prevent.

8.) Inspect your flywheel before removing your governor. A previously damaged flywheel can break apart at a completely unpredictable speed. Damage may not be visible (spit happens) but if it IS visible, replace it.

9) If you have to remove your flywheel for repair/maintenance, remove it properly. Do NOT beat the he// out of it with a BFH or pry on it. Invest in a flywheel puller. Failing that, try the following: Loosen the retaining nut until the nut is flush with the end of the shaft. Now, hit the nut squarely and sharply a couple times with a hammer. Most times, this will do it. You can also aid in loosening the flywheel with mutiple taps around the circumference with a soft-faced mallet or deadblow hammer. Do NOT beat on it with a steel hammer.

10) If you need to hold the engine from turning while you are tightening/loosening a crank bolt or clutch, do NOT wedge a screwdriver or bar in between the flywheel fins. Although this is not likely to crack the 'wheel, a fin could break off. This will throw the 'wheel's dynamic balance off. An out-of-balance 'wheel is just asking for trouble. Same goes for sawing off alternate cooling fins (an old performance trick). If your fins are cast into the 'wheel, don't do it. If you have a Honda, clone or other engine with plastic fins, go for it.

11) Handle with care. Once you have the 'wheel off, don't drop it...

So- Armed with the above information, go ahead and make an informed decision. This guide arms you with what you need to know, to decide whether removing your governor is a feasible idea, and how to handle things if you do. And remember (for all the "Armageddon-is-coming-prepare-to-meet-thy-maker-in-a-sintered-metal-flywheel-induced-world-war-3-esque-everybody's-gonna-die-including-the-cockroaches-in-the-cupboard"-nervous-nellies out there... Spit happens. On the one hand, your stock flywheel will very likely be fine. On the other hand, even a performance parts could fail. Spit happens.

One last point here- For those that may not yet be ready to dive into their engine and come out with a handful of governor parts- Some engines (most notably Hondas and clones) have a VERY user-friendly means of governor adjustment. This adjustment is designed to fine-tune the governed speed to spec, but makes it super easy to gain a few hundred RPM- usually you can bring your GOVERNED MAX to 4000-4200 RPM with the turn of a screw. Your governor will still do it's job, but you'll run a little faster. Locate the manual throttle control on your engine- the little lever you would slide to increase or decrease RPM if you didn't have a remote throtte (gas pedal). Behind that lever is a screw with a spring wrapped around it- Notice how the throttle rests against the tip of that screw when you move the lever to the "fastest" position? Great. Remove that screw. Presto- instant maximum RPM increase- no fuss, no muss.

It is also worth noting that these engines were designed to run at 3600 RPM, day in and day out. If you do run faster, the engine will wear faster. Fact of life. Treat it well, maintain it well, and you'll never notice the potentially shorter lifespan.

Governed Idle FYI

The governor is a seriously misunderstood engine control system. For the greater good, here's a little FYI, an experience I just had. Might benefit someone in the future.

Where were we? Ahh, yes- the governor. Contrary to popular (mis)belief, the governor does much more than limit engine speed to 3600 RPM. Wonder why it's not called a "rev limiter"? 'Cause there's more.

The governor's purpose in life is not so much to limit RPM, but SET it. What's the difference, you ask? (I swear I just heard one of you ask that!) The difference is this. SETTING an RPM means KEEPING it throughout the workload. Let's use a lawnmower for example. You start the engine on your walkway and run the throttle up to max. The governor sets the engine to 3600 RPM, and there is no load (not cutting grass). As you move into the grass, the engine starts encountering a load. The governor allows a throttle increase to bring the revs back up to 3600. Cutting away, you encounter a thick patch over the septic tank. As the engine begins to bog and the revs start to drop, the governor allows the throttle to open more and bring the revs up to 3600. Cool? Great. Going around the corner thru that thick grass with the throttle wide open, you hit that bare spot where the dog keeps peeing. The load comes off the engine, and as it begins to increase, the governor closes the throttle to prevent over-revving and holds at 3600 RPM. Got it?

If you examine your external throttle linkage, you will notice that there is no direct connection between the hand throttle control and the carb butterfly. Governor again. The hand throttle does nothing more than alter the spring tension between the governor arm and the throttle butterfly. Setting the manual control to "Idle" merely alters the spring tension from the governor enough to allow it to SET engine idle speed. The idle adjust screw is the bottom end rev limiter in that it sets the baseline that the governor drops to. I told you that to tell you this:

I recently had a situation that some folks might misdiagnose- an engine that refused to idle properly. After a barrage of time, abuse, and adjustments, the chinese Kohler clone on my kids' kart would not sit at idle. The kart constantly wanted to take off with no throttle input. At a glance, the idle was too high.

Close examination revealed that the idle stop screw on the carb was not doing anything- the butterfly just would not rest against it. If I pushed the lever by hand, it would sit at idle RPM, but as soon as I let go, it would take off again.

I tried to adjust the external governor components to no avail. With the arm off the shaft, something just did not feel right inside the engine. I pulled the engine off the kart and tore it down. I don't even know how to describe what had happened inside, but the governor guts were all over the place- literally.

By some miracle, nothing was really damaged. Short version of the story? I epoxied the "press-fit" governor gear shaft back into the side cover and reassembled everything. I (re-)adjusted the external components, and wouldn't you know it? Idles like it just came outta the shipping container at 1310 RPM, and maxing at 4230 as measured by my optical tach. Food for thought."


r/minibikes 1h ago

Tech Question Carb confusion

Post image
Upvotes

Recently swapped in a predator ghost engine to my Baja doodle bug, as I was taking everything apart to set up the throttle cable. This little clip fell out of the throttle piece and I don’t know how it went inside it. What is it called and how do I reinstall it?


r/minibikes 6h ago

Other hello guys I’m just getting back into the mini bikes again I’m having trouble with it squeaking when started I’ve it’s been sitting for over a year I put a new carb ,changed the oil put gas a new clutch aswell but I’m still having troubles if anyone can help id appreciate it

Enable HLS to view with audio, or disable this notification

2 Upvotes

r/minibikes 16h ago

Other Things purely a money pit

Enable HLS to view with audio, or disable this notification

19 Upvotes

It seems any time somethings going alright, it breaks. I got a torque converter and did everything I needed to get it to work. But I completely forgot that this thing can decide when to break the only thing I need to get home. Pushed it a couple miles back home, in hot and humid temps. Don't recommend.


r/minibikes 11h ago

Other Is this ok loose new to motor swaps but just trying make sure I’m doing it right

Enable HLS to view with audio, or disable this notification

3 Upvotes

r/minibikes 18h ago

Showing Off Predator 224 head ported and polished

Thumbnail
gallery
7 Upvotes

Figured id go ahead and finish this today since ill begin working on a 14cc gx160 head for my buddies 212 here soon.


r/minibikes 21h ago

Tech Question Need help asap

Post image
10 Upvotes

i haven’t gotten this bike to ever run really good, and now it won’t start. it barely runs with throttle. i have a 160 main and 30 pilot in my mikuni tm 24mm flatlside. all my gasket are on right and intake and exhaust are tightly on. i have 22lb springs and 256 cam with billet rod, plug is gapped to .30 and flywheel is .40. Valve lash is set to .003 intake and .004 exhaust. does any one have any ideas what my bike just is such a pain to get tuned right?


r/minibikes 22h ago

Other Drum brake return spring hack

Thumbnail
gallery
11 Upvotes

I hit the button on my cheap ass umbrella one day and the top just shot off the handle 10 feet like a SAM. So i saved the spring. Wouldn't ya know it fits on a drum brake cable perfectly. Brakes return great now since it's much stiffer. The original spring was dog ass. Plus you get enough spring for life from one shitty umbrella. So always hoard random junk, you may use it one day lmao


r/minibikes 15h ago

Tech Question Anyone is south la area do mini bike work?

0 Upvotes

Looking to install a predator 212 motor and a new clutch for my mini bike who in south la (usc area) do honest work


r/minibikes 1d ago

Showing Off Buddies 212 dropped a valve

Post image
8 Upvotes

I havent taken a look at it in person but someone I know bought a 212 off amazon like a week ago and dropped a valve. He hasnt opened or modified the engine in any way so its likely the stock keeper wasnt installed all the way and popped off.

I couldnt find him a cheap 224 or a new 212 head so I have him a 14cc gx160 head on the way. Ill be porting, polishing, and potentially shaving it down for even more compression. Ill post my work on it around mid september.

Has anyone else had this happen to them or know someone who has? I wonder how common it is on amazon motors.


r/minibikes 18h ago

Tech Question Using stock breaks with a 60mph build predator 212cc

1 Upvotes

Does anyone else run stock breaks on a built 212cc 60mph and is it duable gonna be spending 300 on getting the whole engine built by a technician won't have the funds for the hydraulics yet saved up can I still ride. Thanks for tips!


r/minibikes 1d ago

Tech Question Minibike idle backwards?

Post image
3 Upvotes

I got a new carb and I don't know what I did, but the throttle thingy(black thing with the spring) is all the way to the wrong side


r/minibikes 1d ago

Tech Question Where to start?

4 Upvotes

I'm new to this but I'm very hyped, are you guys building your own mini's, do you guys have any tutorials?


r/minibikes 1d ago

Tech Question Stock 212 predator need carb recommendation pls?

Post image
7 Upvotes

Hi all, just got an older mini bike that has a brand new predator 212 swap. I’m looking to upgrade the carburetor for better throttle control. Not planning on any performance upgraded, just want a better carb for a stock 212. Any suggestions would be appreciated! thx


r/minibikes 1d ago

Other Father in laws experiment

Thumbnail
gallery
25 Upvotes

We call it the moon rover if you look close he has the tires inside of another tire


r/minibikes 22h ago

Tech Question Predator 212cc

0 Upvotes

I'm going to be upgrading my rod to a billet rod on my predator 212cc and I plan on installing it while the crankshaft is still in along with the rest of the engine I'm worried about my clearance and I don't know how to use Plastigage and remove the crankshaft and check the clearance with a plastigage is that a must or will I be fine, thanks for all the help!


r/minibikes 1d ago

Showing Off new paint

Post image
40 Upvotes

r/minibikes 1d ago

Showing Off Just picked up this janky little thing for a 100 bucks...

Post image
33 Upvotes

Time to learn about it and have some fun...


r/minibikes 1d ago

Tech Question Can anyone help me in troubleshoot?

1 Upvotes

So for some context, I got a GT rascal with a semi built 212 ghost when I got the bike, the parts on the engine were a

Tillitson hemi head
Trumpet exhaust
PWK 24 mm
And a bill aluminum side cover

Long story short, I ran low on oil and spun a rod bearing destroyed, the rod, the crank and the piston so I had to replace all of that and I replaced it with

A flat top piston
A generic bill aluminum rod (stock 212 ghost length)
and a Honda GX 200 crank

So I recently found out that the Tillitson hemi head combustion chamber is 1 to 2 cc smaller than the stock head and a flat piston increase the compression even more Bike feels a little more responsive in the lower end of RPMs, but poles less hard in the higher end and topped out only at 50 when it did at least 55+

If anyone can help me, I’d be very grateful. Thank you.


r/minibikes 1d ago

Tech Question First 212 Swap

Thumbnail
gallery
20 Upvotes

First post here and first swap I’ve done as well. Got this second GMB a couple months ago. It didn’t run. Carb swapped it and put some street tires on it. Rode the hell out of it. And then I blew up the engine.

Decided to go ahead and swap everything out. Engine, carb, exhaust, sprocket, clutch, and chain. My chain has popped off twice which I believe is just an alignment issue but I did wonder if anyone has any advice on whether I need the tensioner or not.

On to the carb issue. I spent the money and got a real nibbi 24mm carb. Throttle response is great. But it won’t stay running at idle. Basically have to cut the choke and hit the throttle. I usually have good luck with the factory settings. But I saw a bunch of different size recommendations before I landed on the 24mm. Probably could have done more research but I just loaded the cart and pulled the trigger. I guess the question is, is the 24mm a good size and do the stock jets have anything to do with the engine cutting out? And I did mess with the idle knob some but didn’t have much luck. Thanks in advance.


r/minibikes 1d ago

Tech Question Header won’t fit right, defective?

Thumbnail
gallery
14 Upvotes

bought this cheapo header from amazon and it feels a teeny bit off. do i have to play around with this more or should i just buy different header?


r/minibikes 1d ago

Other Bought this for 100$ off marketplace lol

Thumbnail gallery
5 Upvotes

Just picked up this mini E bike for 100$ (Monster Moto E250) its made for kids but is the same size as a 50cc pocket bike! It comes with a 24v battery and a 250 watt DC motor stock. The frame is solid it also comes with disc brakes. However it is very slow about 15km top speed with me on it (185lbs 6ft tall) and runs for about 20 minutes until the battery is fully dead.

Does anyone have any recommendations for a faster motor, bigger battery and better controller. My budget is around 400$-500$ max! Id like to hopefully double maybe even triple the speed of what it is currently!

If anyone has any ideas or has done something similar and could offer advice it would be greatly appreciated, thank you!


r/minibikes 1d ago

Other What did I get my hands on?

Thumbnail
gallery
5 Upvotes

My wife stopped to pick up a free Radio Flyer stroller and the homeowner convinced her to take these two with it for free. He said it needs a new battery, but the same battery would work interchangeably for the two. What in the world did she get for free?


r/minibikes 1d ago

Tech Question Does anyone know of a gas tank that fits on the back bar of an mm80?

Post image
1 Upvotes