New Build with pocket bike motor

In 1964 I had a Yamaha 50cc two stroke Sport Bike that could top 50mph. It had a 4 speed transmission which undoubtedly helped but the bike was considerably heavier than a bicycle build so it's definitely possible to get pretty high speeds out of a 50cc.
 
exavid said:
In 1964 I had a Yamaha 50cc two stroke Sport Bike that could top 50mph. It had a 4 speed transmission which undoubtedly helped but the bike was considerably heavier than a bicycle build so it's definitely possible to get pretty high speeds out of a 50cc.
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No doubt. I know a slightly modified 2005 Yamaha Zuma scooter 50cc will do 42mph (according to GPS) with my at the time 230lb butt on it and it is substantially heavier than a bicycle.
Ask me how I broke my collar bone! LOL.wee.
 
good luck getting jim to make you anything!!!! i would throw that thaught right out the window lol cool bike tho
 
How is the vibration? I also have an in frame using a GT50 motor Case Reed with a chain driven 3.25:1 reduction. It runs great and makes great power. I am also using a long tube header. My only complaint is with these chain driven gear boxes makes for big time vibration. My setup really vibrates and takes a lot of the fun out of riding it. How is the vibration with yours?
 
thatsdax said:
How is the vibration? I also have an in frame using a GT50 motor Case Reed with a chain driven 3.25:1 reduction. It runs great and makes great power. I am also using a long tube header. My only complaint is with these chain driven gear boxes makes for big time vibration. My setup really vibrates and takes a lot of the fun out of riding it. How is the vibration with yours?
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Are you sure it's the chainbox causing the vibes?

I've got a BGF kit with a Titan 49cc, and 3.25 single row chainbox that I converted to oil bath.

The whole set-up is very smooth and quiet. barely get someauflg vibes at WOT.

The clutch bell is mounted crooked on mine and shows a lot of wobble when spun by hand with the gearbox off. Maybe that's what's causing your major vibes and my minor ones?
 
old motorbike said:
Just installed gas tank and tried to start, No spark. Took out mag coil and re-spaced it and it started and ran great. The gearing was way too high. I could barely get it going, but it did well, then stalled. After about 3 pulls the pull start broke (chinese plastic).
So I stopped for now. I'm getting a new metal pull start and looking for a way to gear it down, maybe a jackshaft or another gear reduction added on.
the gear reduction is about 3:1 and final chain is 5:1. So I need about another 10:1
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Did you get the gearing worked out?
How did that cheap gearbox hold up to the motor?
thanks
 
It's altogether a nice build, but in my opinion the thing that makes it, and what stood out to me first is the engine mount. Great job building that! :) Looks fun! what kind of speed are you getting with that teeny tiny sprocket in the back?
 
Great build, very ingenious mounts, very clean.
What gear box is that exactly?
You mentioned an oil bath set up?
As a fellow hi pipe rider may I suggest wrapping that pipe with some header wrap... it will save you a nasty burn.
Again, great build, good luck with it.
FR
 
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old motorbike said:
Just installed gas tank and tried to start, No spark. Took out mag coil and re-spaced it and it started and ran great. The gearing was way too high. I could barely get it going, but it did well, then stalled. After about 3 pulls the pull start broke (chinese plastic).
So I stopped for now. I'm getting a new metal pull start and looking for a way to gear it down, maybe a jackshaft or another gear reduction added on.
the gear reduction is about 3:1 and final chain is 5:1. So I need about another 10:1
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3:1 X 5:1 = 15:1. If you're shooting for 25:1, you need another 1.66:1.

15:1 X 1.66:1 = 25:1.

12t/20t sprockets = 1.66:1.
10t/17t = 1.7:1
11t/18t = 1.63:1

Instead of another jackshaft, you could try an 11t sprocket on the gearbox and a 72t on the rear wheel. That will give you 19.62:1 gear ratio, which will work very well. You could also try an 11t/63t sprocket combination for 17.16:1 ratio. Top speed will be faster with 17.16, but you'll have better low end with 19.62:1 gears.

Either gears will be MUCH better than what you have now. All these 8mm sprockets are inexpensive. 11t is less than $10. 72t sprocket is less than $20.

No need for expensive custom-made sprockets. Simply redrill the 63t or 72t for the Happy Time bolt pattern and they fit right onto your rear wheel.

Orrrr, you could get a HD hub from Staton, screw on a 4-hole left-hand freewheel and bolt the 63t or 72t right on it.
 
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5-7HEAVEN said:
3:1 X 5:1 = 15:1. If you're shooting for 25:1, you need another 1.66:1.

15:1 X 1.66:1 = 25:1.

12t/20t sprockets = 1.66:1.
10t/17t = 1.7:1
11t/18t = 1.63:1

Instead of another jackshaft, you could try an 11t sprocket on the gearbox and a 72t on the rear wheel. That will give you 19.62:1 gear ratio, which will work very well. You could also try an 11t/63t sprocket combination for 17.16:1 ratio. Top speed will be faster with 17.16, but you'll have better low end with 19.62:1 gears.

Either gears will be MUCH better than what you have now. All these 8mm sprockets are inexpensive. 11t is less than $10. 72t sprocket is less than $20.

No need for expensive custom-made sprockets. Simply redrill the 63t or 72t for the Happy Time bolt pattern and they fit right onto your rear wheel.

Orrrr, you could get a HD hub from Staton, screw on a 4-hole left-hand freewheel and bolt the 63t or 72t right on it.
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DAX sells the aluminum version of the 72T with the 9 hole bolt pattern precisely drilled for you already for $25. ENGINE_KIT_PARTS_PAGE_2

I wonder where you can get the sprocket for under $20? Is aluminum going to wear fast with this sprocket? Or no because it has so many teeth?

I noticed if you just buy the 72T the center hole is so large to fit onto the hub if you know what I mean. That is because they are made for those fat pocket bike hubs. Dax has his center hole smaller to fit on a bicycle hub.
 
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gera229 said:
DAX sells the aluminum version of the 72T with the 9 hole bolt pattern precisely drilled for you already for $25. ENGINE_KIT_PARTS_PAGE_2

I wonder where you can get the sprocket for under $20? Is aluminum going to wear fast with this sprocket? Or no because it has so many teeth?

I noticed if you just buy the 72T the center hole is so large to fit onto the hub if you know what I mean. That is because they are made for those fat pocket bike hubs. Dax has his center hole smaller to fit on a bicycle hub.
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Here's one vendor selling the 72t sprocket for under $20:

72 Tooth Sprocket for 8mm (T8F) / Scooter / Pocket Bike | eBay

This one is for a freewheeling connection.
 
Thats without shipping. I bought my first 72T from him and didn't want to spend extra on a customer hub freewheel of the other side since they are expensive. So I just bought Dax's aluminum sprocket which I hope does not wear too quickly.
 
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