Pocket bike powered bicycle

GoldenMotor.com

5-7HEAVEN

Well-Known Member
Aug 2, 2008
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I took a good look at your video again. The sprocket on the left-side jackshaft is too small to be 30t. If you change it to twice the size of your engine sprocket, your bike will fly! Same with the sprocket on your rear wheel. If it really is 60t, your performance should match or exceed that of the minibike that the engine came out of.xct2
 

NLbike

Member
Sep 7, 2016
30
6
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Appleton, NL
I'll have to look at it again when I get home.. Stuck in the great white north now for 5 weeks! I have the bike in parts now, hoping I could get the time to give it a proper paint job.. The engine is a 49cc pocket bike engine with maybe 2hp? It only has a simple centrifugal clutch.. No gears.. The sprockets are a 6tooth-60 tooth to a 15t- 30(or 27?)t.. The tires are only 20inch.. There are kits that would improve hp to around 4-5, and increase rpms quite a bit.. Even if I was running an expansion chamber exhaust,that would improve my top rpms.
 
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16v4nrbrgr

Active Member
Mar 17, 2012
1,728
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North Bay
30:1 to 20:1 gearing on a pocketbike engine from crankshaft:wheel woks good for about 30 to 40 mph respectively on 20 inch wheels. They really liven up when you can utilize the high revs with the centrifugal clutch fully engaged. You can lighten the clutch arms and get more pickup, but it makes it difficult to cruise because it will engage at high rpm only. They are incredibly fun engines, with lots of mod potential!
 

5-7HEAVEN

Well-Known Member
Aug 2, 2008
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Sorry I mistook your bike for someone else's one on YouTube. Nice bike man. I'd like to make one like yours, but with shift kit and pedals. Your gear ratio is10.8-12:1. You need 18-20:1 gearing. Simply replace the wheel sprocket gives you 18:1. Your bike will fly. A larger sprocket would give more low end power. Good luck.
 

5-7HEAVEN

Well-Known Member
Aug 2, 2008
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Change your engine sprocket from 6t to 5t. Gearing increases to 21.6 to 24:1. More low end power.
 

5-7HEAVEN

Well-Known Member
Aug 2, 2008
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My mistake. With 20" tires, your effective gear ratio is already 18:1!

At 45kph(28.125mph), your engine is spinning 8500rpm.

You're in the ballpark.:)
 

NLbike

Member
Sep 7, 2016
30
6
8
Appleton, NL
Thanks for calculating that! I know some of the more high performance pocket bike engines rpm are closer to 11,000 so that might be a possible upgrade later! (if the price is right!)
 

5-7HEAVEN

Well-Known Member
Aug 2, 2008
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Your bike brings back memories.

A friend of mine started with a Honda 35 engine with Staton chain drive. It went ok, maybe 30+mph. I sold him a used 460 engine, which got his bike up to 53mph on flat ground. He must've been cranking 13,000rpm!xct2
 

NLbike

Member
Sep 7, 2016
30
6
8
Appleton, NL
Sorry! No developments lately! I've had quite a bit going on and the bike has been put on the back burner for a while! Hopefully I can get back to it once the weather warms up a bit.. Still a foot of snow on the ground here in NL!
 

Ludwig II

Well-Known Member
Jul 17, 2012
5,071
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UK
In Britain global warming has meant that snow has been almost non existent across most of the country.
 

NLbike

Member
Sep 7, 2016
30
6
8
Appleton, NL
Quick update! The bike isn't dead! I disassembled it in hopes of giving it a proper paint job, but I missed riding it! I've just done a little touch up paint job, and I am in the process of putting it together again! No peanut tank from a Harley anymore tho...
 

MEASURE TWICE

Well-Known Member
Jul 13, 2010
2,748
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CA
I don't have a sand blaster, but I should try to do the disassembly also so I can do rattle can paint after sanding by hand and flap disk on my angle grinder. I have seen what people have done without an oven for power coat using infra red I think. Or maybe I'm mistaken and that is just enamel? I have a garage now so I can wait when it is not so darn hot.

Maybe you can make this or another bike with ski attached to front fork in place of wheel. I thought of that when seeing Cushman Mini Bike that way. Just my rear drop outs only have my nobby tire at 2.125" width. The studded tires are interesting, but on two wheel and not in a compartment with airbag, I have some reservations. I was done with an indoor scuba class and was biking home when in my late teens and had my wet hair freeze riding a few miles in the snow.
 

Mikunimike

New Member
Apr 19, 2019
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Hey, I'm new to this site and I wanted to share what I've been working on for the last little while. It started life as a Norco Dirtmaster that I found abandoned in a ditch when I was a teenager. I took it home, fixed it up and drove it as a bicycle for a few years. About 10 years later, my parents were cleaning up their garage and came across the bike again, so I took it back to my place, where it sat for longer, until I was given a pocket bike engine. I made a mounting plate for the engine and that's as far as I got with it until I got a new job close to home with lots of free time! I brought the bike in, and with the helpful donation of a 70s Harley peanut tank, finished it off! It did have ape hangars on it before, but I've always liked the look of café racers.


Looking great ! True cafe racer look, I've done a pocket bike build myself, yours is so much better.
 

NLbike

Member
Sep 7, 2016
30
6
8
Appleton, NL
Thanks for that Mikunimike! Yeah I know.. almost a year until I replied! I just re-discovered this post! I have some ideas for this spring and I hope to resurrect this bike to its full(ish) potential! Just not sure if I want to keep it full cafe racer look, or go a different direction.. My "old" back would appreciate a little more of an upright sitting position! haha! I guess you do have to sacrifice a little comfort for the art of things sometimes!