Stroker Engine Build: 30+ HP on a 65 MPH Mini Bike! (Complete Build)

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  • Опубліковано 7 лют 2025
  • Ever wondered what putting 5x more horsepower onto a mini bike would do? Check out the Honda gx390 performance mods build video that goes over the big block engine swap from the forged piston, billet rod and crank on the bottom end, to the black venom ratio rockers, heavy valve springs, 3 stage header, and flat-slide mikuni carburetor on the top end. Plus a little bit of riding at the end.
    PARTS USED IN THIS BUILD
    Honda GX390 Engine amzn.to/2zQIOrW
    GX390 Starter amzn.to/2uxHdCl
    Predaotr 420/Gx340/390 Billet Connecting Rod bit.ly/2mqzp0I
    Honda Gx390 1.2 Ratio Roller Rockers bit.ly/2LpKfPr
    90mm -.050" compresison height piston bit.ly/2uIlp6o
    GX390 +.200" (70mm) stroker crank bit.ly/2uLyGuT
    GX390 Crank Bearings amzn.to/2JyefHh
    GX390 Oil Seal amzn.to/2NlSxs0
    GX390 Magnetic Oil Plug bit.ly/2NrT4ZL
    90mm .043" head gasket bit.ly/2NYiyic
    35mm Intake Valve bit.ly/2L7ij6G
    31mm Exhaust Valve bit.ly/2zZx0Uz
    Billet Retainer Kit For Valves bit.ly/2mulnel
    GX240-390 & 301-420 50 lb HD Valve Springs bit.ly/2msY98K
    Rotating Assembly Balanced by NR Racing
    GX390 Valve Lifters amzn.to/2L6lifW
    GX390/420 275 Camshaft bit.ly/2No1LEs
    GX390 Crankcase Cover amzn.to/2Jzynso
    GX390 Gasket(s) amzn.to/2uxT1Ez
    GX390 Valve Cover Spacer bit.ly/2uLAFPR
    Cut To Length Push Rods bit.ly/2mthxT2
    Mikuni TM32 Flatslide Carburetor amzn.to/2Ltf9q5
    Billet 32mm Intake Manifold bit.ly/2LtYjHG
    GX390/Predator 420 Exhaust Header bit.ly/2uHhdDV
    40 series Torque Converter Kit bit.ly/2Nsg7U2
    Billet Thumb Throttle amzn.to/2zQHh5a
    Adjustable Throttle Cable bit.ly/2JzAL2k
    TOOLS & CONSUMABLES USED IN THIS BUILD
    Piston Stop amzn.to/2NZNxKN
    Degree Wheel amzn.to/2zPQXwD
    Timing Light amzn.to/2uxhMAX
    Gasket Maker amzn.to/2uxU8Ef
    Bearing Puller amzn.to/2mrjGOP
    Plastigage amzn.to/2moGJKm
    12 Point Socket Set amzn.to/2L2yiTH
    torque wrench amzn.to/2L82pJu
    Feeler Gauge amzn.to/2NYzBkl
    Assembly Lube amzn.to/2NWIMlc
    Dremel Rotary Tool amzn.to/2muFnxE
    Carbide Rotary Burrs amzn.to/2O1Tp6n
    Dial Indicator amzn.to/2zLZNLS
    Green Grease amzn.to/2uwq3F4
    Valve Lapping Compound amzn.to/2O13DnM
    Valve Lapping Tool valve_lapping_tool
    Isopropyl Alcohol amzn.to/2mpX9lz
    50ml Class A Burette amzn.to/2L3Ojsp
    Micrometer amzn.to/2uxvKTo
    Mill amzn.to/2L9rHHi
    Piston Pliers amzn.to/2zRgc1R
    Piston Ring Compressor amzn.to/2uv9NEk
    Dry Erase Marker amzn.to/2uxY4ov
    Caliper amzn.to/2NZlQlt
    Abrasive Chop Saw amzn.to/2uxsB5Y
    Compression Ratio Calculator
    bit.ly/2zSEOas
    Free Go Kart Plans
    kartfab.com/go...
    GET MORE KARTFAB
    / kartfab
    Instagram: / kartfab
    Like KartFab: / kartfab
    Follow KartFab: / kartfab
    KartFab Google+: plus.google.co...
    Rock Intro 3 by Audionautix is licensed under a Creative Commons Attribution license (creativecommon...)
    Artist: audionautix.com/

КОМЕНТАРІ •

  • @adampreston1516
    @adampreston1516 11 місяців тому +1

    That trick where you froze the crank and heated that timing gear was common sense but absolutely genius at the same time.

  • @heatedheavy407
    @heatedheavy407 2 роки тому +4

    I periodically watch your videos, this is one of the best videos I’ve come across. The in-depth explanation all across the board, thank you. I know it’s a few years old but keep up with the great content

  • @trevinskiking2165
    @trevinskiking2165 3 роки тому +2

    And for beginners or ' newbies' you don't sand your piston top - you polish it for improved heat deflection back onto the combustion chamber & in a Hemi you can polish the Head combustion chamber surface too to stop carbon build up aids flame propagation without going into the science of it all.It adds HP & helps to make your engine last longer.If you've milled your piston crown you can get it Teflon coated or polish it to a shine (an old top Fueler speed secret)cheers everyone.T NZ

  • @TheClintmeister
    @TheClintmeister 4 роки тому +3

    One of the best tutorials of engine assembly I have seen!

  • @michaelkafoure786
    @michaelkafoure786 6 років тому +1

    You should clearance the block, connecting rod, and piston before you send it out to the machine shop. you want the crankshaft, connecting rod, and piston to be balanced together. It seemed like he sent the engine to the machine shop, then milled down the piston, and ground some of the connecting rod down. I could be wrong but it wasnt to clear to me while watching the video. Great build and this video had a lot of valuable info on building a small engine. Great job and thanks for sharing it.

    • @KartFab
      @KartFab  6 років тому

      Correct. That’s how it should be done. Video isn’t on chronological order.

  • @liamhills6700
    @liamhills6700 5 років тому +1

    I'm trying to rebuild a GX390 at the moment to put on a go kart, just been trying to find videos to help. This video was the best so far!!

    • @KartFab
      @KartFab  5 років тому +1

      glad i could help.

  • @kevinbrooks4871
    @kevinbrooks4871 5 років тому +1

    Hi Grant Very informative videos your a true mechanic and not just the parts changer like so many others on UA-cam claiming to be a mechanic you Sir are a 100% legit mechanic. You have earned a subscriber here keep up the good work Grant...

    • @KartFab
      @KartFab  5 років тому

      Thank you sir.

  • @ronaldreed7698
    @ronaldreed7698 6 років тому +1

    I've seen so many people use little short rods which put far greater stress on the cylinder and make less power instead of making clearence for rods like you did.
    With a little grinding you can use a 6" rod on a small block stroker which makes more power (stays @TDC longer) and removes the stresses, these engines tend to run cooler as well, all that's needed to do it correctly is grinding like you illustrated.
    Nice job, well explained, if I build one I will follow your lead.

  • @spencerjohnson1499
    @spencerjohnson1499 8 місяців тому

    Yea I'm building a pred 224 stroker and the works I bought a omb side cover clearance plastic checker best tool! I can see all the areas of concern relatively easy and know where to grind its been a great experience. Loved your video thanks! I'll bee watching more of them😊

    • @KartFab
      @KartFab  8 місяців тому

      No probs.

  • @KartFab
    @KartFab  6 років тому

    *PARTS USED IN THIS BUILD*
    Honda GX390 Engine amzn.to/2zQIOrW
    GX390 Starter amzn.to/2uxHdCl
    Predaotr 420/Gx340/390 Billet Connecting Rod bit.ly/2mqzp0I
    Honda Gx390 1.2 Ratio Roller Rockers bit.ly/2LpKfPr
    90mm -.050" compresison height piston bit.ly/2uIlp6o
    GX390 +.200" (70mm) stroker crank bit.ly/2uLyGuT
    GX390 Crank Bearings amzn.to/2JyefHh
    GX390 Oil Seal amzn.to/2NlSxs0
    GX390 Magnetic Oil Plug bit.ly/2NrT4ZL
    90mm .043" head gasket bit.ly/2NYiyic
    35mm Intake Valve bit.ly/2L7ij6G
    31mm Exhaust Valve bit.ly/2zZx0Uz
    Billet Retainer Kit For Valves bit.ly/2mulnel
    GX240-390 & 301-420 50 lb HD Valve Springs bit.ly/2msY98K
    Rotating Assembly Balanced by NR Racing
    GX390 Valve Lifters amzn.to/2L6lifW
    GX390/420 275 Camshaft bit.ly/2No1LEs
    GX390 Crankcase Cover amzn.to/2Jzynso
    GX390 Gasket(s) amzn.to/2uxT1Ez
    GX390 Valve Cover Spacer bit.ly/2uLAFPR
    Cut To Length Push Rods bit.ly/2mthxT2
    Mikuni TM32 Flatslide Carburetor amzn.to/2Ltf9q5
    Billet 32mm Intake Manifold bit.ly/2LtYjHG
    GX390/Predator 420 Exhaust Header bit.ly/2uHhdDV
    40 series Torque Converter Kit bit.ly/2Nsg7U2
    Billet Thumb Throttle amzn.to/2zQHh5a
    Adjustable Throttle Cable bit.ly/2JzAL2k
    *TOOLS & CONSUMABLES USED IN THIS BUILD*
    Piston Stop amzn.to/2NZNxKN
    Degree Wheel amzn.to/2zPQXwD
    Timing Light amzn.to/2uxhMAX
    Gasket Maker amzn.to/2uxU8Ef
    Bearing Puller amzn.to/2mrjGOP
    Plastigage amzn.to/2moGJKm
    12 Point Socket Set amzn.to/2L2yiTH
    torque wrench amzn.to/2L82pJu
    Feeler Gauge amzn.to/2NYzBkl
    Assembly Lube amzn.to/2NWIMlc
    Dremel Rotary Tool amzn.to/2muFnxE
    Carbide Rotary Burrs amzn.to/2O1Tp6n
    Dial Indicator amzn.to/2zLZNLS
    Green Grease amzn.to/2uwq3F4
    Valve Lapping Compound amzn.to/2O13DnM
    Valve Lapping Tool valve_lapping_tool
    Isopropyl Alcohol amzn.to/2mpX9lz
    50ml Class A Burette amzn.to/2L3Ojsp
    Micrometer amzn.to/2uxvKTo
    Mill amzn.to/2L9rHHi
    Piston Pliers amzn.to/2zRgc1R
    Piston Ring Compressor amzn.to/2uv9NEk
    Dry Erase Marker amzn.to/2uxY4ov
    Caliper amzn.to/2NZlQlt
    Abrasive Chop Saw amzn.to/2uxsB5Y
    *Compression Ratio Calculator*
    bit.ly/2zSEOas

  • @markw5805
    @markw5805 4 роки тому +31

    I’ll never do this, BUT this was really good and detailed.

    • @drivingfaild726
      @drivingfaild726 3 роки тому +1

      @@walterralph8885 lol

    • @clickbaitpatrol2375
      @clickbaitpatrol2375 3 роки тому +1

      Lol I’ve watched this video like twenty times now I’m never doing this

    • @trevinskiking2165
      @trevinskiking2165 3 роки тому

      @@clickbaitpatrol2375 When you've done a few, it's like falling off a iog.cheers.Trev NZ

    • @trevinskiking2165
      @trevinskiking2165 3 роки тому

      @@clickbaitpatrol2375 dang autocomplete "log/tree trunk" Trev.cheers

  • @donraabe3529
    @donraabe3529 4 роки тому

    I had know idea that’s what goes into building a gx390. I just picked up a racing mower that has a built gx390 on it. I need to have it gone through. No way I’m going go attempt it myself. Very good video sir...

  • @2000buellm2cyclone
    @2000buellm2cyclone 5 років тому +1

    Why would you pass on all this information, you'll have to race them.
    I'm a Schooled Natural Mechanic turned Machinist and then Engineer. A True Natural High IQ Gear Head.
    You have just showed a lot of true secrets, that I spent a lifetime learning. Building High-powered G.M. Big Blocks and Small Blocks.
    Very Impressive!!!
    Someone has Taught you Very Well!!!!

  • @denseleit
    @denseleit 2 роки тому

    Awesome man. Many years ago I did something similar to the same type of mini bike.. Used a Power fist 420cc engine and a comet belt drive with single into dual mufflers. It was a torque monster lol. Almost 85kmh too.

  • @Bluegrasscamper71
    @Bluegrasscamper71 4 роки тому

    Nice to see a little more in-depth video on an engine build.

    • @KartFab
      @KartFab  4 роки тому

      Glad to help.

    • @jaynardmanuel2653
      @jaynardmanuel2653 3 роки тому

      Thank u boss maybe ive learned a lot on maybe i can and install that on my flat boat motorized bangka

  • @benruether8294
    @benruether8294 3 роки тому

    That Bandit themed kart was awesome! The guage bezel is the same texture as the real Trans Ams. I dig it

  • @MrJameslewis530
    @MrJameslewis530 4 роки тому +4

    8) I can't believe what I just witnessed, truelly amazing build. First video of yours I've seen. The level of precision that went into it. Yeah, I have to subscribe.

  • @Willie_MN
    @Willie_MN 6 років тому

    When you say, after lapping the Valves, they are exactly the way they need to be, I agree on one of the two. The Intake Valve seating ring is correct. The area you lapped in is exactly in the middle of the Valve Face. The Lapping ring is the correct width too.
    The Exhaust Valve has a seating surface that is to close to the outer edge of the Valve Seat face. The ring left from Lapping is about twice as wide as it needs to be. A Valve Seat Cutter (see Neway Valve Seat Cutter Kits - Get the right kit and you can do 3 angle valve job for even better flow) would allow you to re-cut the Valve Seat. By doing this, you would be able to move the Seat Area seen after Valve Lapping so the ring is centered on the Valve Face and the same width as the seating ring seen on your Intake Valve.
    Thank you for the cool video!
    Willie

    • @KartFab
      @KartFab  6 років тому

      thanks for the info! Ive been wanting to do a bit of head work., Instead of doing it myself i got the chance to trade for a head that had a professional port job, milled .100" and true 3 angle valve job with a larger intake valve and seat. I got it o-ringed and will be putting it on the engine soon!

  • @jamest.5001
    @jamest.5001 2 роки тому

    I always put the rings across from each other, because the farthest away from one another is 180° the sight blow-by going through the gap, would have a long way to go having to go through 3rings and around the piston a few times, to get inside the crankcase, the top oil ring does offer some resistance to blow-by, with the drain holes in the oil ring land, the bottom oil ring would not matter to the blow-by,

  • @garrettomar7656
    @garrettomar7656 5 років тому +2

    I’m impressed how nicely it came apart

    • @trevinskiking2165
      @trevinskiking2165 3 роки тому

      Garrett, thats because it had recently been put together at the factory - the gaskets hadn't had time ' to take a set ' they curn em out by the thousands.Trev New Zealand.cheers

  • @ardysmith9987
    @ardysmith9987 5 років тому +4

    Great video sir ,I've been playing with small my whole life an your video is very informative. I'am 50 years old an I love guys sharing information,I try help out as many people who want learn ,an you just showed me a few new tricks thank you .

  • @williamsuleyman3018
    @williamsuleyman3018 5 років тому

    Nice Video ,well spoken ,good clear instructions ,No annoying noise

  • @chicohaze787
    @chicohaze787 6 років тому

    My recent motor is a Briggs Vanguard 7.5 hp that I got in the junkyard for $9 not bad. They were great with me they let me bring my old blowned motors to exchange swap my favorite Carburetor and it runs great.

    • @KartFab
      @KartFab  6 років тому

      those are nice little engines.

  • @bainmccartney
    @bainmccartney 5 років тому +1

    Yo my predator 212cc stock engine does 60mph with a header, jet and airfilter with a bypassed gove. 36T rear 12T centrifugal clutch on 15"x5"-6 "safe" ultimate street tires from go power sports. Tomorrow 18LB valve springs with a tilotson tct mechanical carb

  • @kennethconnors5316
    @kennethconnors5316 5 років тому +7

    nice video, you did a good job explaining everything .will watch more of your stuff

  • @NckGarage
    @NckGarage 6 років тому +35

    I would love to see this thing on the dyno. Next it would be cool to see less stroke and a really big bore and make it a really high revving engine and see how it compares. It would likely cut down on the torque real low but add HP up top. Great video by the way

    • @KartFab
      @KartFab  6 років тому +8

      yeah, the dyno is all set up. Youll have to wait about a month to see the video though as I have other footage im working on now.

    • @BuzzLOLOL
      @BuzzLOLOL 6 років тому

      Can't make really big bore, there would be nothing left of the metal around it...

    • @ronaldreed7698
      @ronaldreed7698 6 років тому +4

      For a high rev engine, you really need a pressurized oil system, not a splasher. Just my opinion but I'm guessing most here who've modified engines will agree with that assessment.

    • @ronaldreed7698
      @ronaldreed7698 6 років тому

      @@BuzzLOLOL And then heat wont dissipate, it will cause failure.

    • @christophermuddiman527
      @christophermuddiman527 6 років тому

      Hello,,question I have a gx390 also but trying find the correct Crankshaft output Length to fit my new reduction gearbox,,,,, for Belt drive for go-cart,,,,,It’s the most common gearbox,,And China guy couldn’t help with any information. Or understand for that matter. Appreciate your time and look forward to a reply when your able of course. Thank you

  • @aaaabababa
    @aaaabababa 6 років тому +33

    Love these videos, although i am more of a 2 Stroke guy because they are waaaaaay easier to modify, and also i just love to hear small 50-80ccm bikes reving to 13'000+ rpm.

    • @mtnsleder2829
      @mtnsleder2829 6 років тому +3

      PistonBully I like the sound of my weed whacker.

    • @dangerousdoggo5465
      @dangerousdoggo5465 6 років тому

      wtf

    • @elespiritudeltigre9526
      @elespiritudeltigre9526 6 років тому +3

      So you like the sound of an amplified mosquito

    • @drd1449
      @drd1449 6 років тому

      Its not the sound but the power comparated to 4-strokes

    • @hrd8706
      @hrd8706 5 років тому +1

      @@elespiritudeltigre9526 well amplified mosquito sounds better to me than a wet fart.

  • @ssplintergirl
    @ssplintergirl 6 років тому

    You are doing the Lord's work mister.

  • @Greybuiltracing
    @Greybuiltracing 2 роки тому

    One of the best vids I’ve seen on here that reallly went in depth info ! Ty

    • @KartFab
      @KartFab  Рік тому +1

      Glad it was helpful!

  • @lanetruesdale813
    @lanetruesdale813 6 років тому +1

    Good to hold the gear you put on the crank down while everything comes to room temperature they creep up sometimes using that technique.

  • @scrapr65
    @scrapr65 6 років тому +1

    How come you didn't blue check your lap on your valves? And polish the top of your piston?

  • @jaydoeseverything7717
    @jaydoeseverything7717 Рік тому

    Perfectly executed build and video very good work my man

  • @brianboyee8972
    @brianboyee8972 6 років тому +1

    Show me 30 hp on the dyno after its together and i will be impressed,.. its harder to get there than most think. A true 30hp 390 that will survive at that state of build is truly impressive

  • @mingusbreeze
    @mingusbreeze 6 років тому +4

    Thanks, Grant for a bad ass engine build.

  • @starpuss
    @starpuss 6 років тому +13

    *Should be pushing around 25-30HP to the wheels with that work done*
    One year i want to do up a Gx460 clone Block

    • @KartFab
      @KartFab  6 років тому +2

      you could also go with the 500cc bigger block that bullfrog racing has.

    • @brianboyee8972
      @brianboyee8972 6 років тому

      Nope

    • @KartFab
      @KartFab  4 роки тому

      @anonymous nrracing

  • @fundingo11
    @fundingo11 4 роки тому +2

    I’ve learned so much watching your vids! Thanks for all the content! 👍🏽

  • @zoesdada8923
    @zoesdada8923 6 років тому +80

    I've been a welder for fifteen years. I used to teach at the ship yard and to be honest I've seen far worse first time aluminum tig. Far, far worse.

    • @VikingRul3s
      @VikingRul3s 6 років тому +7

      I agree! We once ordered a tig weld for a alu prototype heavy duty industrial "floor" sander. It came back horrible and that was from a pro company (they blamed the learning curve their new brand had). Needless to say, we found a different welding company

    • @stevemartin4529
      @stevemartin4529 6 років тому

      you ok

    • @CatTheGato
      @CatTheGato 5 років тому +2

      Steve Martin of course they are they ditched that dumbass company why u mad

    • @ghost-carnage8964
      @ghost-carnage8964 4 роки тому +1

      You should see the welds my boss does on our equipment. So garbage.

    • @trevinskiking2165
      @trevinskiking2165 3 роки тому

      Kilroy was here ! Xl😋

  • @austintracy6985
    @austintracy6985 Місяць тому

    Cool bike bro love ur techniques for does the engine build

  • @SpeedDeamon95
    @SpeedDeamon95 6 років тому +2

    This guy makes it seem so easy!

    • @mtnsleder2829
      @mtnsleder2829 6 років тому +1

      Because hes a billionaire.

    • @brianboyee8972
      @brianboyee8972 6 років тому

      Because he never proved the hp numbers with the dyno run

  • @llewvirtue861
    @llewvirtue861 5 років тому

    Very good build, I have built many motors, and you are spot on hard to fault

  • @MrArmydad0621
    @MrArmydad0621 6 років тому +1

    Thanks for the video Grant. I enjoyed taking notes on anything I may have missed for the drag bike.

  • @tylerryan4711
    @tylerryan4711 6 років тому +1

    Bob Ross of minibikes! Love it!

  • @Captainkleen
    @Captainkleen 5 років тому

    Very well done. But I’ve always wondered why on engine clearance issues on any mini bike with a faux tank there is always room to raise the engine and put a functional gas tank same teardrop style on having the bike functionally correct with the open top as extra room. Call me old school but that’s what I believe and that is on any mini bike with fake gas tanks look at the mini bike as a real motorcycle you had a good 4+ inches on top to raise the engine. Other then that you did a great job on all your build issues with engine parts and internal clearance. Very well done. Also I have a MM-B212 Mega Moto and bought the front suspension front disc brake setup to make it as close to the MM-212 Monster Moto and found all the parts at Go Power Sports since the company went out of business even another seat. I installed my own LED duel 60 watt headlights but now you have me thinking should I take the new still in the box Predator 212cc Hemi and just get a 301cc or a 420cc and build it to put on my Mega Moto 212 instead. I will run my original for awhile while I build my replacement and put the MM-212 on my Coleman CT200U since I already removed the Governor arm and reconnected everything to the original arm assembly it came with added a .90 jet and air pod and a drop down long header. I want to build a swing arm add rear shocks but not very good at welding after over 25 years of not welding. And I’m looking for a functional teardrop gas tank but the bike doesn’t have that much room from seat to triple trees and it’s a split top bar not single like Baja’s.

  • @a1racer441
    @a1racer441 2 роки тому

    That was a very easy to follow and understand video and not to long thanks.

  • @memyselfandkev
    @memyselfandkev 5 років тому +1

    One thing is that you should always register your start of a buret below the 0.00 graduation and bleed any air in the tip. That is the least accurate portion of the buret

  • @dimaslove9414
    @dimaslove9414 5 років тому +2

    Bro that is dope! Fun at full throttle 💪💯🔥🔥🔥

  • @lizzard7473
    @lizzard7473 4 роки тому

    Sweet video. I'll be inside a 440 this week. Wish me luck!

    • @KartFab
      @KartFab  4 роки тому

      You’re gunna need it! J/K it’s not too bad unless you stroke the engine, then you get all sorts of clearance issues.

  • @E46TY
    @E46TY 6 років тому +6

    You should have left that hose barb on the intake adapter😭PERFECT for a 6Sigma NOS kit

  • @VeePhoutthathad-y3g
    @VeePhoutthathad-y3g Рік тому +1

    Ok thanks you.💯👍🙏

  • @ZestyMTB
    @ZestyMTB 2 роки тому

    I would love to pick your brain on this build. I have something similar in the works and am completely lost on what cam to go with. I’m really curious as to what your piston to valve clearance is.

  • @nickmann5822
    @nickmann5822 5 років тому +2

    First off, anytime you're doing engine internal work, you never touch off with paper. Use an edge finder and do things correctly or not at all. Standard paper is .0045". Now, your piston was made with a tolerance of .009". Slop work. As someone who worked making military components for Helicopters, ect... I had to hold tolerances of .00005. That's millionths. You couldn't pay me to accept work like this.

    • @seraph512
      @seraph512 5 років тому +3

      You can't really compare a $300 mini bike engine to a $25 million+ helicopter my dude.

  • @zerkermond
    @zerkermond 3 роки тому

    That motor has so much torque that's legit

  • @whatsnext8696
    @whatsnext8696 3 роки тому

    That was awesome. Lots of work. Would love a engine like the on my coleman 200u ex.. Great vid.

  • @williamsuleyman3018
    @williamsuleyman3018 6 років тому +1

    I should of been born in Texas ,So much space for endless fun..unlike the Boring wet UK..loved the video

  • @nicovanduin1553
    @nicovanduin1553 6 років тому +2

    Great build! One sugestion though, lock the flywheel in place when torquing down the crankshaft bolt. You wont risk bending your crankshaft that way.

    • @KartFab
      @KartFab  6 років тому

      how would you lock the flywheel in place without damaging it?

    • @nicovanduin1553
      @nicovanduin1553 6 років тому +3

      KartFab I would use some kind of strap wrench. A custom tool that locks the starter ring in place could also be an option.

    • @brianboyee8972
      @brianboyee8972 6 років тому

      What on earth are you talking about guy?,.. have you been inside a GX390?

  • @fabiolus2007
    @fabiolus2007 6 років тому +1

    Started on first crank, hat to you Sir!

  • @eyeballengineering7007
    @eyeballengineering7007 6 років тому +3

    You did a very comprehensive video. I give you mad props for that. I almost did one for my similar big block build (lifan electric start) , knew how much time the video effort would have taken and the notes to say all the details. liked, sub'd

  • @victoryfirst2878
    @victoryfirst2878 4 роки тому

    Nice job rebuilding a mini bike with some major H.P. fella. Look forward to see more too.

  • @sebastiancantarelli6594
    @sebastiancantarelli6594 6 років тому

    Man, it looks so fun!. Congrats for the built.

  • @jamest.5001
    @jamest.5001 2 роки тому

    I'm wanting to build a engine mount /swing arm for one of these engines, and swap it into a Chinese scooter, replacing the gy6 engine, and try to do it so it kinda looks stock! I have a few ideas how to mount everything, I think around 20hp would be plenty!

  • @rattyratstuff7125
    @rattyratstuff7125 5 років тому

    try dimpling the intake after porting. i asked my engines teacher about it in college and he happened to have a flow testing machine in the back room. 455 big block olds hp head. gained 32% flow just from porting and dimpling the intakes. vw was on to something

  • @blairguinea1337
    @blairguinea1337 4 роки тому

    Great build Grant, loved your skill, great job Sir

  • @jons6125
    @jons6125 5 років тому +1

    First time viewer loved the video 👍Where is this dyno stuff you promised?

    • @KartFab
      @KartFab  5 років тому +1

      Took my engine out to race in a rainstorm and washed out the cylinder. Basically ruining the engine. I got a new block to get bored out and am waiting on machine work for that to happen.

  • @delroymoriah4507
    @delroymoriah4507 5 років тому

    Hey nice job I have a 150 cc I bore it and put in a bigger piston I would like to know if I have to port it or it ok just like I want more speed

  • @GGaievski
    @GGaievski 2 роки тому

    ok i just love this video, i watch it every month or so lol

  • @j.chrisbeck7492
    @j.chrisbeck7492 6 років тому

    hey-next time you rebuild, try doing a 3 way valve job on the valves and the seats, do this after the lapping, so you know where to grind off material, and where to keep it. better breathing through your valves improves performance still further, and its a cheap mod. Liking your videos though, keep up the great content.

    • @nyles5761
      @nyles5761 6 років тому

      J. Chris Beck go hug a tree thanks

    • @KartFab
      @KartFab  6 років тому +1

      thanks for the advice! Can you give me $400 for the set of cutters i need? :-)

    • @j.chrisbeck7492
      @j.chrisbeck7492 6 років тому

      no, I cant, but I feel your pain....

  • @superleggera1992
    @superleggera1992 5 років тому

    Jus a tip i learned from RBG! Weld a slide hammer onto that bearing u had a hard time getting out. Works great

    • @KartFab
      @KartFab  5 років тому

      They actually have a tool called a bearing puller. 😅

  • @232Stangpwr
    @232Stangpwr 6 років тому

    Build update? Any new riding adventures? Lets see some more action and a top speed run. Awesome video man.

  • @ronaldreed7698
    @ronaldreed7698 6 років тому +3

    First pull out of the box! Woohoo

  • @slimjim119
    @slimjim119 6 років тому +3

    Engine sounds great and it's quick

    • @mtnsleder2829
      @mtnsleder2829 6 років тому

      They sound amazing with larger valves.

  • @randomvideos3026
    @randomvideos3026 6 років тому

    On the valve geometry the rollers are supposed to be in middle at HALF LIFT your where centering them at 0 lift

    • @KartFab
      @KartFab  6 років тому

      You got the first half of that astute observation correct.

  • @BicycleMotorsports
    @BicycleMotorsports 6 років тому

    Very informative video. I intend on putting a 212cc predator or Honda 163cc on one of my bicycle frames in the near future. I'll be viewing your channel for tips and tutorials. Keep up the good work.

  • @oldschoolrepairshop2866
    @oldschoolrepairshop2866 6 років тому

    i heard polishing the valves can help build alittle horse power.but this video is great i am working on building up my old hot rod mower to do racing

  • @raulsandoval7395
    @raulsandoval7395 6 років тому

    What a beauty ha..i can image tht on a go kart ...great work man.

  • @holdenbostocky1998
    @holdenbostocky1998 4 роки тому

    Only criticisms are I would’ve put the governor plug bolt in from the outside and trim the bolt head if needed. Other one is I would’ve welded the backside of the hole too. I can’t really say anything because I’m no professional but just my 2 cents.

  • @MrEvtmazda
    @MrEvtmazda 4 роки тому

    Great video. I need friends like u guys

  • @papabits5721
    @papabits5721 4 роки тому

    I was in the pool! Great job and great tips.

  • @ricardoromanowski3073
    @ricardoromanowski3073 6 років тому

    the weld doesn't leak, but most likely the bore for the bearing is oval now. check it using an bore gauge.

    • @KartFab
      @KartFab  6 років тому

      You are probably right. I don’t need that bearing as it is for a counterbalance that was removed. The rotating assembly was balanced afterwards.

    • @ricardoromanowski3073
      @ricardoromanowski3073 6 років тому +1

      thats great news, because usually when you insert bearings into oval bores they don't really like it. Glad you could achieve your preferred balancing-factor even without the countershaft. For removing bearings like this one: Either degrease it and insert a fitting shaft with some loctite 638 on it into it so you can pull on that shaft, or just turn the engine in a way that this bearing could fall out and then heat its surrounding using a propane torch and use a very light hammer or a wrench to softly tap against the case surrounding the bearing and it will fall out.

  • @gooblio
    @gooblio 5 років тому

    Did you check the amount of side to side play in the crank. You usually get some thin washers to shim it if you have over .010" play?

  • @richardschultz2732
    @richardschultz2732 3 роки тому

    Would you consider building one of these for my mini cup car if so how much and how long

  • @petertrom4397
    @petertrom4397 6 років тому +5

    That is awesome! Fantastic job. I love it!!

  • @tommy23490
    @tommy23490 6 років тому +3

    Great video.. Very detailed and complete.. Thank you

  • @hommie789
    @hommie789 6 років тому +1

    Not sure how often you crack open your engine after you rebuild them but if the term "as little as possible" then I would highly recommend gloves when dealing with "friction bearings" oh how i hate that term. But the rod and main bearings are covered with babbitt which is very sensitive to acid, even that which is on your fingers. The bearing is negatively effective by causing low hour wear of the bearing. Just a FYI

  • @BlackDevill9
    @BlackDevill9 2 роки тому

    I have a sawmill with a gx 340. 11hp im no expert but, can it be done on a gx 340 Verry interesting to see the 390 get more power, I wonder if the gx 340 boosted if its possible like the 390 would work in a sawmill application? It would be cool if it did! any thoughts 👊

  • @MRT_H
    @MRT_H 6 років тому +1

    We totally need to drag race when I get my bike done.....Also, candle wax for the blind hole bearing removal helps.

    • @KartFab
      @KartFab  6 років тому +1

      hit me up when you got it done. There are always opportunities with texas outlaw mini bikes to drag race or at least have an informal drag near the dirt track race.

    • @MRT_H
      @MRT_H 6 років тому +1

      KartFab Will do! Texas isn't too far 😁

    • @brianboyee8972
      @brianboyee8972 6 років тому

      Meaning it will never ever happen

  • @xxzenonionnex7658
    @xxzenonionnex7658 6 років тому

    My brother has a 3hp briggs on his and hes tired of going slow so can i take the gov off and not have to worry about anything because it looks like every thing is the same size in the 3hp as my 5hp gokart except the valves amd the engine block and crankshaft so idk if it would have any probs with the gov off because it looks like it has a 5hp piston rod or conrod so will i be throwing a rod?

  • @irome2241
    @irome2241 2 місяці тому

    Great video..awesome build.

  • @anthony1113
    @anthony1113 2 роки тому

    Do you have any vibration / balance issues with removing rear gear assemble?

  • @dosilecreations6229
    @dosilecreations6229 3 роки тому

    was there a reason u didnt port and polish the head? good video

  • @t-dogracingandoffroad3198
    @t-dogracingandoffroad3198 5 років тому

    I locked up one of those things because I got stupid and put a nos kit on it for racing I had to do the exact same thing you did in this video

  • @allblackeverything9975
    @allblackeverything9975 3 роки тому

    Great video sir what size engine is this ??

  • @vortecturbo
    @vortecturbo 6 років тому +1

    Hey man I really dig your videos I have a performance shop down here in Houston, if you need any port work man feel free to hit me up. Be glad to help you out I have over 1k in porting equipment. I love these little small engine projects. Keep up the great videos!

    • @KartFab
      @KartFab  6 років тому

      When it comes to a race head, there is no substitute for a professional engine builder's work on the valves and ports. I kinda just did this to show what a DIY guy can do. No flow bench, port diameter increase, or 3 way valve jobs done. I leave that to the pros.

    • @vortecturbo
      @vortecturbo 6 років тому

      @@KartFab I am a professional cylinder head, intake and supercharger porter 20 + years. I like what you do, that's why I was offering my services to you.

  • @tonyfremont
    @tonyfremont 4 роки тому

    That's the way you do things right. The only thing I didn't see is crankshaft end play checking.

  • @mannyabraham9951
    @mannyabraham9951 3 роки тому

    Good day sir, i would like to know more about the cost of modifying this engine. I am based here in , Ontario, Canada. Do you do an 18hp modification and how much would cost me. I am sending it to the philippines. thank you.

  • @brianboyee8972
    @brianboyee8972 6 років тому +21

    All kinds of claims of “wait till you see the dyno numbers”,..
    But he never posted the dyno numbers~ anyone else notice that?

    • @nicovanduin1553
      @nicovanduin1553 5 років тому +1

      Prolly cause it made like 20 horsepower😂

    • @buder5116
      @buder5116 5 років тому +2

      heard from someone else that these minibike are too small to be on a normal dyno
      something about wheel needing to be 1.5x bigger than the dyno

    • @ahnurmom_187
      @ahnurmom_187 4 роки тому

      he made a dyno for go kart engines

    • @ahnurmom_187
      @ahnurmom_187 4 роки тому

      @@nicovanduin1553 how do u gain 7 hp from all those mods?

    • @ahnurmom_187
      @ahnurmom_187 4 роки тому

      @@noidontthinksolol those engines arent knockoff engines their honda a name brand

  • @erikhobbs1695
    @erikhobbs1695 4 роки тому

    Love seeing that you’re racing in Fort Worth I would like to know more due to the fact I’m in Burleson

    • @KartFab
      @KartFab  4 роки тому

      Check out the texas outlaw mini bikes group on facebook

  • @nealc1308
    @nealc1308 6 років тому

    I would like to know if you build for customers because I would love to get one done by you. Love it by the way great stuff!

    • @KartFab
      @KartFab  6 років тому

      Might want to try calling up gopowersports and ask for Taylor. I don’t normally build engines and this one is $$$$$

  • @haidenoakland297
    @haidenoakland297 6 років тому

    You should make a detachable wheelie bar for drag racing and you can take it off for dirt track

  • @mtnsleder2829
    @mtnsleder2829 6 років тому

    Kraft Dinner you should try aluminum stick welding.. Makes a real nice job.

  • @terrancebarrett727
    @terrancebarrett727 6 років тому

    Nice build! Really badass sounds great!