Custom bicycle with scooter engine

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karolis94

New Member
Jul 23, 2011
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Lithuania
Custom bicycle with scooter GY6 engine

Hello, greating from Europe :) I can finally share with you guys the latest pictures of my new motorized bicycle. I have installed 50cc GY6 scooter engine during the spring break and modified it during the summer. Current engine specs:
82cc cylinder kit;
harder valve springs;
camshaft with longer lobes;
free flow air filter;
free flow exhaust;

I have designed it to run on E85 fuel by advancing ignition timing, increasing compression ratio and richening the air/fuel mixture;


You can find more photos on my facebook page (click there)

It only needs some fiberglass fairings.
If anybody have any questions feel free to write a comment.
 
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wheelbender6

wheelbender6

Well-Known Member
Sep 4, 2008
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TX
Welcome to the forum. Most members haven't built anything when they introduce themselves to the forum. You are already a master builder.
That is the first bicycle I have seen with a GY6 engine and CVT transmission.
The velomobile guys have been using coroplast for making body panels. It does not look as good as fiberglass, but it is much faster and cheaper.
 
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nelsonk1969

New Member
Sep 29, 2014
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Lake Worth Florida 33467
Hi very creative build, what's up with your rear rims? obviously they are not off the shelf.
from the pictures some of the welds would have me nervous if I was to ride it.
do not anything I say personal I am just curious and perhaps worried about your safety.
 
Dan

Dan

Staff
May 25, 2008
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Moosylvania
Howdy and welcome, Karolis.

Awesome build! I have been dying to use a GY6.

How did you attach a sprocket to the CVT? If that the GY6 transmission.

Again, really cool build. Has a Mad Max sort of look.
 
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karolis94

New Member
Jul 23, 2011
8
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0
Lithuania
It is definitelly the unique project :D
I appreciate all your comments. Bike runs great, tops at 40mph (65kph), has a lot of low end torque, carb just needs a little tweaking. I have ordered the performance CDI which should aid the difficult starting issue due to advanced base timing. I even think about arduino controlled ignition system.

The rear rim is holding up nicely, I inspect it for cracks after every ride.

I have attached the sprocket to the wheel hub which I cut off from the rim.
I will try to post more photos, just tell me what part interests you the most.
 
Dan

Dan

Staff
May 25, 2008
12,765
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Moosylvania
Your whole build is fascinating. Really is. In imagenering (made up word for imagining and engineering) I always get stuck on how to use or bend/attach a sprocket to drive the drive chain.

That has to be the most perfect, mass produced, engine ever made for our crazy. Intrinsic generator/alternator. I can't see one in your pics but kick start if electric start fails. Compact, great power and can get parts, performance parts and after market parts any where. And is mass produced (all) so is kinda priced well.

Just all around, a great choice of power plant.

LOL, sorry. Went off on a tangent there.

I'd really enjoy seeing how you mounted the sprocket to the CVT. If possible and ask what your top and bottom gear ratio is?
 
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karolis94

New Member
Jul 23, 2011
8
0
0
Lithuania
This engine is a real gold for builder :D In stock form it can run a few thousand miles without engine rebuild. However, engineering inperfections and cheep design cause some problems when you run it on its edge. Electric starter can't handle my 14 bar (200 psi) compression. I can barely start it this way. Kick starter is designed to be used on emergencies only, because of that whole kick starter assembly wears down quickly. That is true that you can find a lot of performance parts really cheap.

I will post more detailed information and pictures on weekend when I get home :)
 
Dan

Dan

Staff
May 25, 2008
12,765
115
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Moosylvania
Cool! Thanks and safe trip.

I did not know that about the kick start. Big time important with a CVT and no other way to get her started if the electric fails.
 
Ludwig II

Ludwig II

Well-Known Member
Jul 17, 2012
5,071
783
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UK
I can agree with Karolis, I've had the starter from a Piaggio apart, and they have to be kept clean and greased if they are to work at all, and the metal quality is not all that good. It isn't helped by the pedal shaft running directly in the nasty cheap monkey metal transmission casing, instead of a decent bushing.

I'm going to suggest something that is normally only used on bigger engines. An exhaust valve lifter, something that holds it open just enough for there to be no compression while the electric start is whizzing round, and then when the engine is fast enough, let the valve go to normal operation.
 
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karolis94

New Member
Jul 23, 2011
8
0
0
Lithuania
It is quite simple to attach drive sprocket to any scooter wheel hub. To align the sprocket in center of the hub I have used a marker on a running engine to draw circles approximately where sprocket holes should go. Then I drilled them out one size bigger to leave some room for adjustment.
https://www.dropbox.com/s/e0842doounkz2yx/PA030402.JPG
https://www.dropbox.com/s/4ucllavbszyfc91/PA030400.JPG
https://www.dropbox.com/s/9yrzf6p256zcqp7/PA030401.JPG
https://www.dropbox.com/s/11b65eszeyf1lcz/PA030403.JPG

Final gear ratio is something like 28:38. With this ratio engine can rev up to 9000 RPM
 
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