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Mounting Techniques for Bicycle Motors Every frame is different. Share and ask questions about mounting your engine kit to your frame or rack

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  #1  
Old 02-26-2014, 09:08 PM
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maniac57 maniac57 is offline
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Default Rack mounting a chinagirl

Lately I've been thinking of a way to use some of the full suspension bikes I have laying around.
I'm leaning towards rear mounting the engine on a rack above the wheel and using the regular chain drive/ragjoint setup since I already have several rims assembled with sprockets.

This would allow the suspension to function without chain problems and looks like it will work quite well. I'll simply cut the intake manifold to use the straight section which will level the carb nicely. I will mount the tank above and behind the motor on a stand. The pipe will be easy to route along the framestay.


This is a mock up on the narrow crank german made Sears frame I am currently messing about with. This would instantly solve all crank clearance issues too!



Roughing out the engine cradle with some welded steel angle and a section of frame tube. Also have a rear rack-like section of pocketbike frame that will make a good solid platform for this. I'm hoping to have a chain adjustment feature built right into the motor mount. The rack section with the motor and mount will attach to the rear framestays.
One worry is the length of the cables...
another is butt clearance from the spark plug and head...
But it looks doable and I have seen very few rear mounts.
Opinions?
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Last edited by maniac57; 02-26-2014 at 09:18 PM.
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  #2  
Old 02-27-2014, 06:48 PM
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Default Re: Rack mounting a chinagirl

It does look do-able, I gotta admit.

But won't you still have to deal with chain loosening/tightening when the suspension flexes?
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Old 02-27-2014, 06:58 PM
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maniac57 maniac57 is offline
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Default Re: Rack mounting a chinagirl

Not with the engine mounted to the rear suspension swingarm. It all moves as one unit.
There are some differences between mounting it on a regular bike and the suspension bike so I'm going with a mongoose frame I found somewhere for the initial design. The pics are from a solid frame and I'm not going to bother with this style frame just yet. I like the idea of opening up a suspension bike market for chinagirls with a true bolt on, but the first few prototypes will probably be welded solid to the frame. Time will tell.
I'm thinking seriously of making a kit if it works out like I hope, but first things first.Have to see if it works.
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Old 02-27-2014, 09:10 PM
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Default Re: Rack mounting a chinagirl

Somewhere, way back, a member posted a picture of a rack mounted HT. He had done a very nice job of it and the little engine looked like it belonged back there.

There was also another bike, I'm talking maybe 2008 or 09, that was a twin engined affair. One HT was in-frame, the other was rack mounted. I have no idea where I'd find those today but if they turn up I'll post them here. Maybe someone will remember those oddities and will refresh my memory as to where I can find them.

Good luck with your project. Sounds interesting and feasible. Keep us posted.

Tom
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Old 02-27-2014, 10:01 PM
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Default Re: Rack mounting a chinagirl

The longer I stare at it, the better the idea looks considering how cheap and numerous the suspension bikes are.
I'm finding it hard to believe nobody else has had this idea before. I really expected a lot more input from other with similar brain(storms)farts.
It just seems so easy and universal...
I'm hoping it works as well as it looks.
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Old 02-28-2014, 06:48 AM
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Default Re: Rack mounting a chinagirl

Butt clearance...lol...

Butt seriously...lol

No this looks awesome bro...
Try easing the motor behind about 6 inches...

A neighbor did a rack mount 48...

Walmart seatpost rack...tigged some aluminum supports to the rack and bolted down by the rear axle...

2short aluminum tubes tigged to the plate on the rack and the chain ran down thru the side slot...

On a full suspension too...it works well...

You can definitely do it...

Good luck brother
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Old 02-28-2014, 07:54 AM
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Default Re: Rack mounting a chinagirl

This is a great idea, for the plentiful CG engines. I have built several rear mount full suspension bikes using 4stroke engines. Kind of an apples/oranges comparison but it may show how easy a susp. frame can be modded. If you made a pivot type mount with two supports that were slotted chain adjustment would be a snap! http://motorbicycling.com/showpost.p...8&postcount=10
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Old 02-28-2014, 07:09 PM
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maniac57 maniac57 is offline
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Default Re: Rack mounting a chinagirl

Did some more fiddling today.
Got the rack setup welded on solid


Welded a cradle on to hold the motor. Looks nice and solid. Can't deflect it by pulling on the head so it should be fine. The pipe will be easy to run as well.


I still have to bob the intake to level the carb.
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  #9  
Old 02-28-2014, 10:59 PM
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16v4nrbrgr 16v4nrbrgr is offline
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Default Re: Rack mounting a chinagirl

Nice job Maniac, a rack mount that will have some serious 66cc torque! Most rack mounts use the whacker/pocketbike engines that lack in that dept, and I'm thinking about upping the displacement of my BMX using a 52cc pocket bike engine to be able to gear higher and still enjoy the torque that only CC's can supply.
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  #10  
Old 03-01-2014, 07:08 AM
gokart25 gokart25 is offline
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Default Re: Rack mounting a chinagirl

I've been considering selling my 4 stroke stuff... Just wondering if something like this would work with a 79cc predy? I like the design!!
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