Pocket Bike engine on a bicycle - Pocket Bike Forum - Mini Bikes
 
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post #1 of 14 (permalink) Old 11-18-2008 Thread Starter
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Pocket Bike engine on a bicycle

Hi i currently own a x18 and a bicycle with an engine kit on it. Over on motorbicycling.com we have been discussing installing a 47cc motor on a bicycle. With our 67cc kit supplied china made engines we can only safely see about 6000 rpm. They also do not produce much power and vibrate like all h*ll but I am personally seeing 150+mpg and ~34mph max (cruising at 25mph). My bike has 1100 miles on it and has required little maintanence, in fact i have one of your guys' expansion bikes on my bike (although cheap china made one.) So Im asking you guys over here if a second gen 47cc engine will get us closer to 45mph and still have good mileage? Or is the 49cc non-reed valve motor better (cant see how)? What engine was fitted to 2nd gen cags? Anyone have a motor for sale or free? I know your engines are of higher quality than ours and will most likely be more reliable.
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Last edited by europorsche914; 11-18-2008 at 08:41 PM.
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post #2 of 14 (permalink) Old 11-18-2008
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Re: Pocket Bike engine on a bicycle

check Welcome to Tsunamibike: direct importer of pocket bikes,atvs,dirt bikes,mini motorized bikes... best prices!!! They have a special engine for bicycle like a 80cc ones with everyting u need to run, even gas tank and chain! Check under the new products section and u will see it

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post #3 of 14 (permalink) Old 11-18-2008 Thread Starter
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Re: Pocket Bike engine on a bicycle

yea thats the same kit i have its claimed 80cc but is actually 67cc... typical chinese stuff just like how my x18 does 70mph stock Thanks for your quick response and let me tell you though that price is pretty competitive especially if thats the shipped price. -Justin

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post #4 of 14 (permalink) Old 11-18-2008
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Re: Pocket Bike engine on a bicycle

For the weight of the bicycle, I don't think the pocketbike 47cc engine will have enough torque for it. But I know a guy in my area runs a X-7 four stroke 49cc and works good...and he is fast on the road.

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post #5 of 14 (permalink) Old 11-19-2008
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Re: Pocket Bike engine on a bicycle

It would probably be a good "helper" engine on a bicycle though. I remember I had a original apache bicycle(you know the ones from 70\80's with the big chopper handlebars, big seat, and big 3-gear stick shifter) a few years ago, **** do I regret giving that frame away.. Would have been a boatload of fun to have one of these small engines on that bike! Gotta get myself one of those again if they can be found still!

Vroom, Vroom, BOOM.. - Hmm, aint that something..

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post #6 of 14 (permalink) Old 11-19-2008
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Re: Pocket Bike engine on a bicycle

i would stick with that 65cc!! it looks to be a better set up but of coarse you'll need to change the port timing up and do a couple mods to get better performance. i wouldnt even worry about gas mileage no matter how many mods you do you wont be able to tell a difference in gas mileage.

by the way whats the bore and stroke of this motor you have? if the stroke is longer then 32mm you definitly wanna keep it!
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post #7 of 14 (permalink) Old 11-19-2008 Thread Starter
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Re: Pocket Bike engine on a bicycle

The stroke is 40mm and the bore is 46mm. Unfortunately some of these motors have rods stretching; crank bearings wearing out; and if its a roller bearing motor, complete engine failure within 500 miles; and all have poor 6.5:1 compression. On my motor i have port matched everything, changed the intake timing by enlarging the port and lowering the floor (piston-ported engine with 2 transfer ports), changed the exhaust timing by enlarging the port and raising the ceiling, and an expansion pipe. I'd say my acceleration to top speed(~34mph) is in the 10sec range. Apparently someone on motorbicycling.com did install one of the pocketbike motors on his bike but didnt supply details other than that it was very fast until the down tube broke... Here's the thread on MB: The Pocket Bike Engine and Your Opinion... - Motorized Bicycle Engine Kit Forum
The amount of replacement parts and performance parts for your engines is amazing... I thought i heard that a 2 stroke motor and a 4 stroke motor of equal displacement, a 2 stroke will be faster and lighter than the 4 stroke. Let me know what everyone's thinkin, I still hope this could work!
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post #8 of 14 (permalink) Old 11-19-2008
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Re: Pocket Bike engine on a bicycle

These places have the best engine kits for a bike that gives years of service if broken in and mixed properly;-the 80cc kit will push a bike up to 40 mph and better...............................Peace


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post #9 of 14 (permalink) Old 11-19-2008
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Re: Pocket Bike engine on a bicycle

I always used to put chainsaw engines on my bikes. I have one ofv those chopper bikes set up with one right now too.Would give u guys pics of it but its at my uncles for a tune up.
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Re: Pocket Bike engine on a bicycle

Have you considered changing the gearing? It sounds like you could safely trade some acceleration for higher top speed.

That engine looks really interesting. Are there better pics anywhere?
post #11 of 14 (permalink) Old 11-19-2008 Thread Starter
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Re: Pocket Bike engine on a bicycle

Yea thats the same kit i already have and the quality is lacking. I could change gearing but then it would require pedaling to get up hills... More pictures at Pictures and Videos - Motorized Bicycle Tavern at Motorized Bicycle Forum
Not sure about the credibility of the claimed downhill speed but its still movin pretty good: YouTube - 49cc Mountain Bike. Pocket Bike Conversion 3 Speed 80+km
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Re: Pocket Bike engine on a bicycle

you need to add a reed cage which will allow you to boost port the cylinder. you then need to either mill the head or shave the top of the cylinder to bump your compression way higher! you should be at 10-13:1 not 5.6:1 thats way too low! its the same with those jr50 motors once you get the compression raised a reed conversion and 20mm carb they move like they're supposed to. going to a cag engine would be taking a step backwards you should take advantage of that long stroke and bore! the polini's and bzm's only go as high as 39.8mm on the stroke with small 40mm bores and they'll get you to 60mph!
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post #13 of 14 (permalink) Old 11-20-2008 Thread Starter
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Re: Pocket Bike engine on a bicycle

Maybe I should just stick with this motor. Hopefully the one machinist that is interested will help us improve this engine by creating better parts. Thanks everyone for your input. This is the first thread i have ever started since i know how to use the search button... What a great site! -Justin
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Re: Pocket Bike engine on a bicycle

Quote:
Originally Posted by europorsche914 View Post
Yea thats the same kit i already have and the quality is lacking. I could change gearing but then it would require pedaling to get up hills... More pictures at Pictures and Videos - Motorized Bicycle Tavern at Motorized Bicycle Forum
Not sure about the credibility of the claimed downhill speed but its still movin pretty good: YouTube - 49cc Mountain Bike. Pocket Bike Conversion 3 Speed 80+km
For what I heard....it is illegal to ride the above bicycle on the road....coz it has gears....

Being legal on the road...you can only have one gear, can't shift.

that's the case in my city, should check with your local policeman

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