what should i get??

Discussion in 'General Questions' started by jjeeff, Feb 17, 2015.

  1. jjeeff

    jjeeff New Member

    I have a trek 7.2 fx with disk breaks, what engine kit should i get?

  2. darwin

    darwin Well-Known Member

    Nice bike. You need to narrow your criteria down to your personal needs/choices. There's simply too many choices out there. 2/4 stroke, in frame, rack mount, Friction drive, gearing etc..................good luck!
  3. KCvale

    KCvale Motorized Bicycle Vendor

    Are you talking about this Trek 7.2 with front and rear discs?


    If that's the case it's a no-brainer.
    A jackshafted 2-stroke is the way to go.
    You keep both disc brakes and your engine can use the 7-speed gears on the rear wheel.

    This is a similar build.



    ~$400 for a DIY build and a rewarding ride if you have the building skill and tools to install the shift kit properly.

    Just my opinion as always, meaning what I would do with said bike.
  4. troyg

    troyg Member

    No place more than MAB's have I found the saying "you get what you pay for" is more true.
    As Darwin said, you need to figure a few things out first.
    I will add: the more complex, the more things to come loose.
    If you like to tinker, frame mount china girl, if you want to ride FD or GEBE WITH quality engine.
    If you're going to do any kind of serious jumping, frame mount is the only real option.
    Any and all are fun fun fun.
  5. jjeeff

    jjeeff New Member

    KCvale: so that top trek bike is defiantly the one im talking about. So do I buy the 2 stroke engine separately and then buy the jackshaft kit?
  6. bikejock

    bikejock Member

    I've seen disk break kits specifically designed for motorized bikes. The rear disk is significantly larger so they can fit over the engine kits rear sprocket. Don't know if that would work on most bikes tho. Frames with disk breaks are usually made in such a way that if you want a motor on it you'd need to switch to a V break. If your worried about breaking power most of that comes from the front break anyway so keep that a disk break and change out the rear for a V break. I plan on fitting my GT Dyno Deuce cruiser with a motor in a few months and that bike only has a rear coaster break but I can swap out the front fork and front hub for ones that are disk break compatible because I wan to keep the original rims.

    from what I've read about jack shaft kits, a jack shaft kit is good for going faster changing gears and helps you keep both front and rear disk breaks but most states if you want to ride a motorized bike without a license, registration, and insurance it can only be one speed from the engine to the rear wheel. In most states the legal definition of a moped/motorized bicycle that doesn't need a license, insurance etc. is often a bike that has an under 50cc engine with fully operative petals and no gears.
    Last edited: Feb 18, 2015
  7. KCvale

    KCvale Motorized Bicycle Vendor

    Yep, some states specifically state no gears, Arizona is not one of them ;-}

    Yes you buy the motor and shift kit separately, mount the jackshaft base to the back of the motor, then mount the combo into the bike.

    Is this your first build?
    Are you really good with tools?

    If it's your first build and you are not handy with tools it might be a bit more than you can do.
    If you want to give it a go get the deluxe kit.
    It has the specialty parts and tools you'll need.

    You have 3-piece cranks on the Trek so that makes the bottom bracket easier.
    It's still a complex job though, there is no room for error or slop when you are redirecting ~3HP of spinning force around.
    http://www.sickbikeparts.com/Manuals/SBP2 Manual001 Rev A.pdf

    Good Luck!
  8. jjeeff

    jjeeff New Member

    yes this is my first build. i was going to pay someone to put it on for me because i am not the most handy with tools, but that is proving to be just as hard as finding out what i need to buy. But i think im gonna go for it im going to get the jackshaft delux kit a 50cc engine and find a mechanic who i think is up to the job. Thank you for your insight and help
  9. Arty

    Arty Active Member

    I agree with KC. Installing the shift kit isn't rocket science, but you do have to be careful with chain tension, sprocket alignment etc., and for me anyway, it took a bit of tweaking after first assembly, and obviously, there's more to go wrong than with direct drive.
    They are fun though, and it's easier to keep the bike on the pipe at varying speeds, and to keep from thrashing that poor little engine at high RPM at road speed.
    I do miss engine braking though, because of the extra freewheel on the pedal crank.
  10. jjeeff

    jjeeff New Member

    KC: If it isn't to much to ask could you send me a materials list for the Gray Trek 8.3 48cc Shifter that is on your website? Im just confused if there is a specific type of 50cc engine i need, they all look different. And the gas tank and exhaust pipe? Will any of them fit onto any 50cc motor? I feel like its a elementary request but i just don't wanna buy something that wont work.
  11. KCvale

    KCvale Motorized Bicycle Vendor

    Just contact me from my web site or post in that bike builds topic.

    Every build is different so I need a reference in the conversation but sure, I'll share, it's not like it's a secret ;-}
  12. jjeeff

    jjeeff New Member

  13. jjeeff

    jjeeff New Member

    And i thought a 4 stroke would be better because i will be riding like 10 to 20 miles on it everyday, is that true or am i crazy?
  14. KCvale

    KCvale Motorized Bicycle Vendor

    There is a Contact link on my top menu.

    No, those parts won't work.
    That is a 4-stroke engine, it won't fit in your V frame, you need a 2-stroke.
    That shift kit is garbage, it's a knockoff of the original SickBikesParts kit without a solid base and has the junky freewheel bearing.

    Chrome pipe and tank won't hurt anything.

    I posted the link to the sickbikes jackshaft with the extra tools you'll need.
    Just get a 2-stroke kit to attach it to.
  15. jjeeff

    jjeeff New Member

  16. KCvale

    KCvale Motorized Bicycle Vendor

    That is the right jackshaft kit, but it looks like they are out and they won't get in until mid March.
    Thank the dock workers on the West coast for that and many other things you can't find.

    That is the proper engine type for your project.
    It looks like you want to stay under 50cc, wise if you simply can't afford another run in with the law.

    I don't know what to think of your $120 motor kit choice though...
    Fantastic 49cc 50cc Bicycle Engine Kits for Motorized Bike 2 Stroke Petrol Gas


    That is their E-bay product description pic, not mine, jezz...
    Looks like a 66cc base with a 48cc head and then the whole thing dunked in a bucket of paint.

    Except the silver parts, every nut, bolt and screw look to be painted into permanent place.
    Black engines look neat, but you don't paint the whole darn thing into place.

    Looking for the best 2-stroke engine kit bargain is usually not the way you want to go when you are going to be spending days attaching more to it, then the combo to the bike to see if it even runs and will continue to.

    Personally I like Skyhawks but I just picked up a couple these last week.
    One is in a bike and it's a nice clean well made engine with good kit parts like a bigger 2.5L tank and some parts you won't use with shift, but parts none the less.

    If I'm not mistaken the Yang Dong factory (China Gas) made Black Stallion and Flying House 2-stroke engines as well.

    Bottom line is you can spend money riding around, or spend it fixing it wishing you were riding.
  17. jjeeff

    jjeeff New Member

    I wast trying to skimp out on a good engine kit i just couldn't find a complete 2 stroke kit on the gasbike website, as you've probably deducted i am not the most technologically advanced person in the world. This is the most time ive ever spent on the internet, just trying to find out what i need for my bike. and i really do appreciate your insight it has literally guided my search entirely. so if i get: http://www.gasbike.net/48cc-black-stallion-2-stroke-bike-motor-kit.html that engine kit and then the jackshaft kit from sick bike parts I will have everything i need for installation? And once its installed will i still be able to pedal the bike manually if it like runs out of gas or something?
  18. KCvale

    KCvale Motorized Bicycle Vendor

    You'll probably need a front mount from sickbikeparts as well to fit your front down tube, you will have to measure yours to get the size.

    That's should do it, and yes you can pedal with the engine off, you have to pedal it to start it ;-}
  19. jjeeff

    jjeeff New Member

    ****, the parts are on the way. Now ill play the waiting game thank you again for all your help ill let you know how it goes and send pic when its done!