mounting motor on/above top bar - massif fatbike

misterb · Jun 24, 2014

Wanted to get some thoughts from the experts here -- what about the possibility of mounting a motor above the top bar on a Mongoose Massif (20" fatbike) by using a longer seat post to make it 'adult sized' like the pic below:

Ideally a small 4stroke and a qmatic if that were possible.

wheelbender6 · Jun 24, 2014

I have seen it done with a GX-35 clone, but it takes a lot of fab work, jackshaft, etc. I would add a friction drive kit instead to preserve those great disc brakes.
Where did you buy that thing? I want to test drive one myself.

misterb · Jun 24, 2014

I haven't picked one up yet - one of the neighborhood boys got one and I was envious

I found the pic above online. I guess I could live with a friction drive, but only if I could center it - I have a thing for symmetry, can't stand the motors hanging off to one side.

I haven't seen them in stores yet - you can order online via walmart, target, academy sports, etc for < $200

wheelbender6 · Jun 24, 2014

Offset mounting the engine on a friction drive setup allows you to mount the engine lower, for better handling. The lower cg really helps when leaving and approaching a stop.
If you mount a fuel tank or cargo box on the opposite side of the rear wheel from the engine, you can maintain some symmetry.

curtisfox · Jun 25, 2014

Kooool if it were me and realy wanted to do it I would cut the tubes off and make new. Nice curved drops loop and maybe split the top into two out around the motor if needed just my thoughts...........Curt

misterb · Jun 26, 2014

curtisfox said:
Kooool if it were me and realy wanted to do it I would cut the tubes off and make new. Nice curved drops loop and maybe split the top into two out around the motor if needed just my thoughts...........Curt

I think it IS a steel tube bike so at least it'd be easier than aluminum.

2door · Jun 26, 2014

Not being a naysayer but I always look at things with safety or the potential for injury in mind. I can't help but think what would happen in a sudden stop with an engine mounted high between your legs. Not a pretty thought.

I'd have to explore another option to motorize that one. Friction or rear rack chain drive would be a better choice, me thinks.

Tom

misterb · Jun 26, 2014

2door said:
Not being a naysayer but I always look at things with safety or the potential for injury in mind. I can't help but think what would happen in a sudden stop with an engine mounted high between your legs. Not a pretty thought.

I'd have to explore another option to motorize that one. Friction or rear rack chain drive would be a better choice, me thinks.

Tom

good points to consider!

lowracer · Jun 26, 2014

misterb,
Like you were thinking, I mounted an engine to my top tube via a piece of angle aluminum. I run the chain to the large chainring via a front freewheel and then another chain from the small chainring back to a 9 speed cassette. It worked out really well!
Here is the link
http://motorbicycling.com/showthread.php?t=50454&page=13
-Lowracer-

misterb · Jun 27, 2014

lowracer said:
misterb,
Like you were thinking, I mounted an engine to my top tube via a piece of angle aluminum. I run the chain to the large chainring via a front freewheel and then another chain from the small chainring back to a 9 speed cassette. It worked out really well!
Here is the link
http://motorbicycling.com/showthread.php?t=50454&page=13
-Lowracer-

wow - thanks, that's just the kind of thing I was looking for. I actually already have a gx31 I got for about $50 on ebay.

mapbike · Jun 27, 2014

In my opinion the only thing that will not totally jack the looks up of that bike would be a nice custom built friction drive set up, anything between the seat post and the handlebars is not gonna be nice looking and I'm with Tom on the safety aspect.

cool looking bike for sure but the engine and drive set upo needs to be at the backif I were doing it.

Here is a set up that would work good on that bike, sets the engine center of the bike, no good up close pix of the design but it wouldn't be that hard to build from what I can see.
http://youtu.be/Ec03Vbd1_yM

misterb · Jun 27, 2014

regarding saftely concerns, if i really wanted to stick with fat bike with 7 speed cassette, i could just move to the dolomite (if I can find enough room within the frame):

2door · Jun 27, 2014

curtisfox said:
Kooool if it were me and realy wanted to do it I would cut the tubes off and make new. Nice curved drops loop and maybe split the top into two out around the motor if needed just my thoughts...........Curt

I'm with Curtis on this. If I was going to motorize that bike, and it would be cool, I'd modify either the top or the down tube to accomodate a 2 stroke in frame installation.
That will require some fabrication, tube bending and welding but it would be worth the effort in the end. You'd also have to get creative to retain the rear disc brake but it can be done. Good luck. Let us know what you decide.

Tom

wheelbender6 · Jun 28, 2014

I was looking at a post about the GX-35 and saw this thread.
http://motorbicycling.com/showthread.php?t=53529

mapbike · Jun 28, 2014

wheelbender6 said:
I was looking at a post about the GX-35 and saw this thread.
http://motorbicycling.com/showthread.php?t=53529

looking at this photo Im thinking that isnt gonna work unless engine is set up to run counter clockwise, unless there is a gear box on the other side that causes the output shaft to rotate counter clockwise when the engine is runnng clockwise... there must be a gearblox that just cant be seen.

2door · Jun 28, 2014

Yes there was a gear case.
I've ridden that bike, or one just like it, with that weird engine installation. That chain running down next to my leg was scary. I kept imagining it breaking and wrapping around my neck. Not a great idea.

Tom

wheelbender6 · Jun 29, 2014

I was thinking that you could mount a typical beach cruiser chain guard on the motor chain. Then I realized the the chain guard would need to be a left side drive version to work.

mapbike · Jun 29, 2014

fabricating a chain guard for that set would be very sime and if I had a bike like that it would dang sure have one, there would be at least one or maybe two guide rollers built into the guard also, a chain that long needs something to insure alignment and correct tension in my opinion, or one wrong bobble during a leaning turn and that chain could come off.

myself Im not sure Im a fan of an engine being mounted up under my chin while Im cruising down the road at 30 mph....lol!

map

lowracer · Jun 30, 2014

Regarding my top tube mount, I use a piece of angle aluminum to guard the drive side of the chain more for oil flying up, than for safety since I've never had the engine driven chain fly off. The chain from the BB back to the rear cassette came off once or twice in the beginning, but I fixed that by mounting a larger chainring to the inside of the 24T chainring acting as a chainguard.
I thought about running all chains within chain tubes (similar to a recumbent) but since I haven't had any more derailment problems, I didn't.
-Low-

Bzura · Jun 30, 2014

You can fit (barely) a HT engine in the Dolomite with a shift kit. I did it, and it's lots of fun. I had to get a longer 5/8 keyed shaft though, but that wasn't difficult to swap out.

View attachment 71098

mounting motor on/above top bar - massif fatbike

New Member

Well-Known Member

New Member

Well-Known Member

Well-Known Member

New Member

Moderator

New Member

New Member

New Member

Well-Known Member

New Member

Moderator

Well-Known Member

Well-Known Member

Moderator

Well-Known Member

Well-Known Member

New Member

New Member