ON MY FIRST BUILD From Pearland , Tx

[stage3gt]

Hey guys im starting my first build! Im just a 16 y.o. kid trying to have some fun! i know i will be into this hobby for a while so i want to get started off on the right foot! i will be using my bike to just cruise around so the most i would need out of it is about 40mph,,i want more acceleration than top speed!

i will be using one of these engines!

http://www.ebay.com/itm/53cc-54cc-2...es&hash=item20c025e1f4&vxp=mtr#ht_2165wt_1185

and this is the bike i have!

http://www.youtube.com/watch?v=FxYR3awR36s

i wont be using the bicycle engine like i say in the video since i found the nice little 50 cc engine on ebay. i want to know if any of you guys know how to do the gearing and that stuff? thanks

 

[a_dam]

i will be using my bike to just cruise around so the most i would need out of it is about 40mph

HAH! Is that all? 30mph is fast on a bike. 40 must be scary. That motor might be able to do it. My connection is too slow to open that video to see what kinda bike you have (would be easier if you just tell us).

But a 26" bike tire at 40mph is 515 rpm. That motor has a 6-tooth sprocket. If you had a 60 tooth on the rear wheel, that would be 10:1 reduction. So your motor would turn 5150 rpm at 40mph. That's really not nearly enough reduction. At 15:1 the motor rpms would be 7725. That's not a bad rpm for top speed, but your rear sprocket would have to be 90 tooth. It aint gonna happen without a gearbox or jackshaft setup. (unless you do friction drive)

That's why most people here use bike motor kits. Even with a good kit you will have to be mechanically handy. Without a kit, you will REALLY have to be ready and willing to do a lot of "crafting".

But whatever route you go, if you are serious, then this is the right place to get good help. I'd like to see that motor working on a bike.

 

[stage3gt]

i want to do the jack shaft! i dont like the way the gearboxes look they are hideous!
how would i go about gearing the jack shaft?
the bike is a gt palomar 7 hard tail i think its a 98 and had an internal hub gear setup nut i changed those wheels out for a set of cruiser wheels!

 

[Dave31]

Welcome to the forum stage3gt, glad you joined us.

 

[Texhun]

Welcome to the forum little dude! I'm wondering though why not just get a kit? It will save a heck of amount of time and with the stock sprocket you'll get plenty of torque and you'll pay almost as much for the kit as you would that one engine. Just out of curiosity, what are you trying to build exactly?

 

[stage3gt]

Texhun ,
I'm not little lol! I'm a 225 football player! Anyways i would rather have something that not too many people have. Also after all the upgrades such as the head, expansion chamber, decent engine mounts, ect. it will be a lot more than the pocket bike engine actually!..
I want something with a lot more reliability and these engines are the way to go after the things i read about them on the forum. I have also seen that these have more power than the kits and thats what i need for my body type lol!

 

[a_dam]

OK.

You're 16, 225 lbs. You want that powerful motor for a lot of acceleration. The easiest method would be rack-mount friction-drive.

The ebay ad for the motor said "performance clutch". Is that centrifugal or cable operated? Are you planning to keep and use the pull start, or will you be bump starting?

Doing a friction drive means there is no need for jackshaft gear reduction, chains and/or belts and pulleys and/or sprockets. No need for extra strong rear wheel.

Even if you don't want friction drive, a rack mount would make it SO much easier to mount and align the parts you'll need.

Of course, you probably need that motor in-frame because it will looks so cool, like a motorcycle. And there will be something to fix about every five rides.

 

[Texhun]

Or to save a little hassle, why just save up for the Dax 9hp 50cc? Yah it'll cost close to $500 but you'll have all the power you could wish for and then some, plus it's already a kickstart engine. Trust me, no one else in your town will have a bicycle that has power like that. Just gear that baby with a 72T sprocket and you've got a wall climbing machine.

 

[stage3gt]

a_dam ,
yes i want in frame and ill make it work

Texhun ,
thats my next project i already ordered the pocket bike engine

 

[Texhun]

MMHMMM! So begins the fabbing. This is going to be a fun build worth watching. Keep us posted when you get the engine, I'm curious how fast this thing will run, plus I've also wondered how to mount one of these. I guess we're all gonna learn something from this one. This is Exciting! I just watched your video and you said a 40 sprocket, that's a good mid-size sprocket you'll get a little bit of everything but if you want the torque get a 44, if you want top end get a 36 or 32 sprocket. If I'm right these engines redline at 8500RPM. So it's really, it's deciding if you want a hill climber, drag racer or board tracker.

 

[wheelbender6]

If you enjoy tinkering as much as riding, frame-mount the pocket bike motor and solve all the associated problems. If you would rather ride that tinker, get a China girl 2 stroke kit and hot rod the motor. You can make your bike stand out and still enjoy easy motor installation. Customize with paint, motorcycle fuel tank, saddle, fork, fenders, etc. Spend time in the photo gallery subforum and mountain bike subforum to get ideas. That distinctive GT frame is enough to help make it stand out. Just my opinion.

 

[stage3gt]

wheelbender6 ,
i have been looking around quite a bit. i already have the design in mind thats why im being so stingy the engine setup. im going to mount the gas tank in front of the neck of the bike. i will have the motor mid mount on rubber bushings because the the way im mounting it it vibrates alot. i will have a 11 tooth up front and a 72 in the rear.it should turn out to be a sick looking bike when im done!

 

[curtisfox]

Got to watch this build sounds awesome. Welcome aboard...........Curt

 

[a_dam]

a_dam ,
yes i want in frame and ill make it work

That's the spirit. If you know what you want, you gotta go for it. I'm not trying to talk you out of frame mount. Mounting a motor in a frame isn't a huge deal. It mounts in the frame of a pocket bike, after all.

i will have a 11 tooth up front and a 72 in the rear

Does that motor have built-in reduction? The "China girl" bike kit motors have a gearbox, so the motor sprocket (10 tooth?) spins at 1/4 the motor rpms. Most people use a rear wheel sprocket of about 40 tooth. So the final ratio is about 16:1. I think you need a pretty strong motor to get away with 16:1; for max torque, people shoot closer to 20:1.
There's no way around that. An 11t front/ 72t rear will give you 6 1/2, you'll need to multiply that by about 2 1/2. If that motor has some kind of trans, then you can have a chain from motor to rear wheel.

 

[stage3gt]

a_dam ,
yes i will be using the 3:1 reduction gearbox!