the leathal threat !!!

Discussion in 'Photos & Bicycle Builds' started by rogergendron, Sep 27, 2013.

  1. rogergendron

    rogergendron New Member

    here is my first well first in a long time motor bike build ( when i was 12-15 i built a few chainsaw wakker bikes lol ) it called the leathal threat and took a few days and about 300$ to build

    its a single speed 26 inch beach cruiser with hub brakes the back pedal kind, i chose that style to keep the handle bars free of cludder. the motor is a grubee gt5 66 cc when i first got it in the mail i was not impressed with the quality of it at all !!!! and thought it would barly run ! and the mix ratio of 16:1 was insane who runns a motor that lean and full of cheap oil ? but i put it together as is and rode it stock on a crappy mountain bike to break it in and test it out and tune it up. well i found that it wouldnt idle for nothin and it had harldy any power and smoked like hell and it was fouling plugs like crazy ! so i said to hell with this thing and pulled it from the test bike and began the tear down.

    i am a great and pretty damn expearianced mechanic when it comes to 4 stroke motorcycles and atvs i restored a honda act 200 3 wheeler (big red) a few years ago... new cam wizco piston high comp head cluch mods the works and the thing is a beast ! so i will aply mu knowage to this and give it all i had with as little $ as possable.

    first i tore the top end off and found tons of carbon and real crappy casting of the combustion chamber dome and the ports were so bad i cant believe this thing runs ! even the intake z manifold had huge burd and casting flakes protruding into it !

    - i decked the head down about .1 and polished the chamber and cleaned up the finns
    - i ported the heck out of the jug taking about an 1/8in off the bottom of the intake and 1/8 off the top the exaust and widend bolth by a 1/4 and decked down the jug a little cleaned up transfer ports
    - port matched the intake and exhaust
    - ported intake manifold nice and smooth
    - modded the exhaust baffel removed cat and driled 4 1/4 in holes in the cap
    - lengthend the intake with a short tube
    - new piston ring (mollybendium)
    -cut 5/16ths off the entire intake side of piston skirt
    - ground 4 ramps in the top of the piston to make a 4 leaf clover pattern alowing air fuel to travel over the piston at bdc easyer and out the jug at down stroke faster... the piston is way lighter now ! and the decked head make up for the compression lossed from the grinding
    -made a thin copper head gasket about half the stock thickness dindnt measure lol just knew it would help comp.
    - nkg b5hs plug hard wired to ignition (no plug boot)
    - adjusted clutch properly and oiled gears
    - replaced clutch ball bearing and rod with brass rod a little longer about 1/16 and new bearing 5/16 the old one had a flat spot it was so soft !!! and greases that hole with 80w lucas gear oil.
    - silicon caulcked the wires coming out the stator to protect them from elements
    - replaced all nuts and bolts with stainless steel ones
    - made custom front motor mount that bolts strait through the frame for a more solid mount.
    - rebuilt the carb and tunned it to new setup.
    - painted to my likeing with flat black vht engine paint

    the results ? the bike has an unbelievable amount of more power than before ! i can cruse at 30 mph no problem for long periods of time and it has massive tourqe for a little engine as it pulls me up even the steepest new england hills at 20mph no problem also it rev's up way quicker and has a much broader power band !!! and i hardly spent any money at all with the mods i did !!! the only thing i bought was a new plug and a 2 inch piece of hose !!!!!!!!!!!!! if you have a dremal tool then you should have at your motor !!! srs power is waiting for you to unlock it ! if you do not have a dremal borrow one or buy one for 30$ the power you get for that 30$ will be more than any bolt on upgrade you can get for this engine in that price range !!!

    i now run my engine at 40:1 full synthetic 93 octaine and my plug looks perfect and the bike idles like a purring kitten !!!! the only thing left to do is make a custom built expantion chamber but that is a whole thread on its own with all the mesureing and math involved !!! with a good custom made expantion chamber and the right length header i think i can get 40-45mph out of this motor with just a swap out fromm 44 to 40 teeth on the sprocket !!! right now i cruse at 25-30 right at the power band but she will pull 35 on a flat. 45 is possable with a good tunned exhaust and a slightly smaller sprocket.

    IMG_20130919_003223.jpg IMG_20130919_003239.jpg

  2. rogergendron

    rogergendron New Member

    planning on a jaguar ignition and a custon made tourqer pipe for broad powerband and 40 tooth sprocket in the near future ... i just need to dish up some money ... and that will be it for this motor ! when the bottom end finaly wheres out i am replacing the whole motor with a preditor engine ... prefeably the biggest one that will fit ! i think i can squeeze a 212cc in there with the right mounting plates welded to the frame . why spend 200$ on parts repairing a cheap china 2 stroke when i can buy a huge beastly degoverned 4 stroke to replace it for 100$ and get rediculus speeds up to 55-60 mph and masive tourqe @ 8,000rpm all from a nice and simple race kart cintrifugal cluch ???

    i cant wait for this to break.............:evilgrin:
  3. bluegoatwoods

    bluegoatwoods Well-Known Member

    Impressive. It's a nice looking bike. It sounded like this is your first 2 stroke china girl engine. Yet you modded it like a pro. Good job.

    Now I gotta be a bit of a downer. Forgive me. It's because I'm concerned about your safety. Please don't dream of going 40, 50 mph and more. Even going 30 is asking for trouble. Bicycle wheels, bearings, tires, etc., are just not that strong. You're all too likely to end up as road splatter.

    Drilling through your frame for the mount was a mistake, too. It weakened your frame. That could also make you hit the road. I know that the sellers include those mounts. But they shouldn't.

    But from the looks of what you've done to your engine, I'm willing to bet that you'd be capable of fixing this issue. Maybe weld a sleeve around the section that you drilled through? Then fab up a motor mount that'll fit around your downtube.

    It looks like you've got the talent to be an MB expert. Just be careful that you don't get yourself killed first.

    Best of luck.
  4. Fabian

    Fabian Well-Known Member

    I see trouble on the horizon for the OP.
  5. professor

    professor Active Member

    Let me guess what Fabian sees wrong?
    BRAKES - one day you will need to stop NOW and you will crash and be maimed or killed because the wimpy rear coaster brake was designed to bring your bike to a stop from about 8 mph.
    That brake was first developed about a hundred years ago when all there was consisted mostly of dirt roads.

    You did a great job on the motor. Being able to stop is vastly more important than being able to go.

    I have 2 bikes with HF engines on them. A 212 and a 79. Neither will rev to 8 thousand.
    Flywheels on the bigger clone motors (like the 212) have been known to literally explode past 6000 (even that level is dangerous)- people have been killed by spinning a cast flywheel beyond it's designed (3500-4000 rpm) range.
    My 212 flattens out at 4500 - the small one at 5000. I purposely kept the governor on the big one. These are sweet motors. I do not ever expect to need to replace one.
    I am still using 40 year old Briggs- these should last beyond me.

    Because of HF's bad experience with the go-kart guys bringing back wrecked motors- they upped the cc to over the kart rule limit, + any motor brought back gets inspected before a new one is issued.
    The big motor is nice for power but mine vibrates- the little one just buzzes. Both have 3 speed SA hubs. Gears are great.
    I wish you well and stay well.
  6. jaguar

    jaguar Well-Known Member

    I have been looking for a better ring to recommend to people reading my site. Please tell where you got it. The standard rings on these engines allow too much blowby. thanks
  7. Fabian

    Fabian Well-Known Member

    Looks like the OP is going to learn this life lesson the hard way, unfortunately the resulting aftermath might call for long term investment in a wheel chair.
  8. 5-7HEAVEN

    5-7HEAVEN Active Member

    Excellent work!

    How about installing a 203mm front disc brake? That'd work well.