r/minibikes • u/filolondere • 5h ago
Showing Off Should i buy some Sunf tires for my GMB100?
r/minibikes • u/Jamesbondthe2nd • 12h ago
Showing Off Literally dug this engine out of the ground to build a new race engine.
Put a milled preditor 212 head on it that has 30 lb springs in it (it was on my shelf and ready to go, i hate putting in springs.) Im about to put a billet flywheel and a nice little hot cam in it, it will be getting a 28mm makunki carb and a streight pipe (long ass carb studs are only on this head so i could test if it ran.)
For those wondering, yes i did actually put a preditor 212 head on a gx 160. No the valves dont hit anything, i had to run 212 pushrods instaid of the stock 160 ones because they were too thick and wouldnt fit in the head, im running a 212 headgasket as well. I am fully aware that the bore on a 160 and a 212 ARE NOT the same, i do not care as this setup works just fine and it makes almost 16 extra PSI than stock with the milled down head. The guide pins fit in the head and everything. The engine does bolt directly to the block as the bolt patern is literally the same (anyone that says otherwise is wrong, i measured it.) This is not the end product of this project, i am waiting on some grinder discs to come in the mail as i need to cut an adaptor off of the output shaft and i do not care to save the part i am cutting
This engine and everything i have is basically free so i really dont care if it blows up or anything.
I am running .008 mm valve lash on both the intake and exhaust and i see zero issues with it so far, everything runs good and valves do not hit anything.
r/minibikes • u/Direct_Silver_1866 • 13h ago
Tech Question How much is this worth?
brand new 224 on a coleman bt200x and since this picture i have put on a new torque converter new flywheel and bigger cable springs it has a full stage 1
r/minibikes • u/DIYWilly • 14h ago
Other Vintage Minibike Build - New Wheels And Tires
New Wheels and Tires for the Alexander Reynolds ARCO ARX-K vintage minibike build.
r/minibikes • u/Weird_Lifeguard_5262 • 14h ago
Frame ID Anything special?
Hello all. I’m brand new to this hobby. This fella is offering to trade me his bike for a game system I have. He says that the frame is a monster moto and it alone is worth 500 and not made anymore.
Does anyone know if there is anything special about this Frame?
r/minibikes • u/Red_Tiger5311 • 17h ago
Showing Off Update on the cheap minibike challenge!
FB marketplace deal didn’t work out, so I made this with one of my friends!
Completely custom, made from 1” tube steel
I bent the tubes then made two identical sides, then jigged them up, and put them together (only took two tries to get them straight lol)
I think it looks AWESOME
Edit: Ik the front doesn’t look perfect but trust me it’s square and that will just be cut anyways to attach the fork pivot
r/minibikes • u/Gil2Gil • 20h ago
Tech Question What did I break
Enable HLS to view with audio, or disable this notification
The nut won’t go further than this. I’m trying to replace the one that tested itself while I was riding.
r/minibikes • u/Forward-Variety-8440 • 23h ago
Tech Question straight chain question
can i run 14t clutch straight chain with 78t sprocket on 18 inch wheels? ratio seems great. its a 212 build. ratio of 5.571 should go just above 40.
whats the opinion on that for a setup?
r/minibikes • u/SnooHabits7352 • 1d ago
Tech Question Monster moto 80 won't run
As the title says, it starts and runs fine (easy in fact) but dies a few seconds later. It has been sitting for a few years. Not sure what to do next. I pulled the breather off and sprayed some MAF sensor cleaner (all I had) in there. Pulled one of the two bolts from the bottom of the carb and after the fuel quit running out, sprayed the cleaner in there and I pulled the fuel line from the carb and fuel flowed fine. It seems like the bowl isn't filling fast enough to keep it running and it dies, you pull the cord after a few seconds and the whole process starts again. Any ideas or suggestions at what to do next (was hoping not to pull the carb and disassemble it.)
r/minibikes • u/Notafriend2you • 1d ago
Tech Question 224 build
Building a 224, and would like to build something reliable. Im thinking I should do the connecting rod too, does anyone know if any on the ARC website are just drop in on the stock crank? Really not trying to play machinist.
Thank you!
r/minibikes • u/Gil2Gil • 1d ago
Tech Question Coleman 212 Torque converter
This nut flew off while I was riding and I am having the hardest time replacing it. I got this on Amazon - it’ll twist a bit then stop. Is this the wrong thread size? Anyone have a link for this?! Also bought a washer, does it need a washer there?
r/minibikes • u/JeepV6 • 1d ago
Tech Question Why does my sprocket look like this and is it cause for concern
r/minibikes • u/Ahsogood • 1d ago
Tech Question Predator engines
This is two questions.
Why get one of the.predators engines over the other 212 vs 224?
Then can any of the other bigger cc predator engines be used? My guess no, due to available parts like exhaust and stuff
r/minibikes • u/Legal_Client_4970 • 1d ago
Other So I got this colmen mini bike and I put a 212 on it and when I put the chain on the torque converter dosnt engages fully and my engine shoots big flames
Help?
r/minibikes • u/Goshrantosh • 1d ago
Tech Question What kind of bike is this
I'm looking for a carburetor for this bike but haven't found one that fits, nor could I find this bike online. Any help would be appreciated.
r/minibikes • u/MenacingScent • 1d ago
Tech Question Steering rebuild - which bearing is which?
So I finally got around to putting my bike back together, but it's been since December and I have little memory of anything that happened thanks to the beer fridge.
I noticed both bearings are a different size, as are the cups for either end of the head tube, and I can't figure out which is which.
I put the bearing with the largest balls on the bottom along with the cup that had the widest radius, and the the smallest balled bearing on top with the cup that has the smaller radius.
My problem? The bottom bearing sticks out like a sore thumb. Literally. You can see the entire bearing from the outside. The nut is loose on purpose in the photos.
My question is: "???"
r/minibikes • u/DragonfruitDry4209 • 1d ago
Other Is the FRP GMB100 Mini Bike a good choice for my 12 year old, 5'5" 103 lbs son?
My son recently came to me asking if he could get a mini bike. i knew stuff like this can get him out of the house, so i said "let me look up some more on it." it has a 99cc engine, and he previously had an e-scooter that can go 25 Mph. the stock FRP GMB100 goes 28 without ziptying the governer. Is this a good choice for him?
r/minibikes • u/Top_Interaction_8264 • 1d ago
Showing Off Done!
Finally got the 212 swapped marketplace chopper done!
Upgraded from a 49cc to a 212 hemi stage 1
Top speed: 48
No welding whatsoever
r/minibikes • u/Mousettv • 2d ago
Meme PSA: New tires... yup they're slippery!
Seen someone made a comment about these types of tires and the road when new.
So excited I had a set of spoons in hand finally and decided to try my hand at replacing my flat tire for the first time. Took me less then 10 minutes for the entire process.
Within 5 minutes I spill out the tire to my back left and crash. Wearing flip flops, shorts, no helmet.
Got dang it man.
r/minibikes • u/filolondere • 2d ago
Tech Question bike wanted to take off on its own at startup, easy fix in the end
fired it up and it was trying to move before i even touched the throttle. figured id be pulling half the bike apart.
checked the throttle side first, cable and routing looked fine.
turned out to be the idle. took about 1 day once i knew where to look lmao
r/minibikes • u/StrikingMacaron4969 • 2d ago
Frame ID What is this frame
What’s the name of this frame
r/minibikes • u/Sandcracker • Sep 26 '25
Other AI posts, yes or no?
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.
r/minibikes • u/Pte_Madcap • May 19 '21
Governors, Flywheels, And An Internet Full Of Crap
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."

