GX120 with 6:1 reduction gearbox.... Need help!!!

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D-MOE

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Hello all,

Don't know why I haven't signed up earlier but I am running into some difficulty with the drivetrain I'm putting in my kids power wheels jeep.

I copied the plans from BigAir that were posted a long time ago.

The problem I've encountered is that the GX120 I have is a 3/4" threaded shaft. I had a HECK of a time finding a 6:1 reduction gearbox for it but ended up purchasing one off ebay.... The seller stated that it was for a 3/4" shaft..... Little did I know, or should have known that the crank needs to be splined. Any solutions to my problem without changing out the crankshaft? Any add on I could purchase? Or would I be better off selling both the engine and gearbox separately and purchasing a unit that's already together?

Your answers are GREATLY APPRECIATED!!
:mad2:
 
landuse

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It might be too much of a mission to make the two work together. Why don't you buy a 2:1 gear reduction box, and sell the other to fund it. I had one that worked great.

Pics of what you have would help us though
 
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D-MOE

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I'm out at work in a camp right now, I'll post pics of the engine and gearbox asap..... The reason I want the 6:1 is my son isn't even 3 yet:p I did the calculations and with the reduction, 10:60 tooth variation and 15" wheels.... The top speed is 4mph...
I'm kinda stuck at the moment.... Thank you very much for the response!
 
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Felineman

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You could try grinding it out CAREFULLY little at a time till the key just fits TAP TIGHT you should be able to pull it out with pliers but not your fingers. Done it takes a steady hand but doable.
 
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D-MOE

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Thank you guys ALOT for the input!!!!
I think I'm going to try and track down that part, looks like my best option! While researching I found the exact engine BigAir used.... It's a 50cc petrol scooter engine that has a 5:1 reduction gearbox already on it. Trying to track down one right now. Anyone happen to know where I could buy one in Canada?
I'll just purchase this and fix the GX120 up for future use. My boy is only 3 so he should get quite a few years out of this build
Once again, thanks a million! Wish I would have signed up 6 months ago lol
 
landuse

landuse

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D-MOE said:
Thank you guys ALOT for the input!!!!
I think I'm going to try and track down that part, looks like my best option! While researching I found the exact engine BigAir used.... It's a 50cc petrol scooter engine that has a 5:1 reduction gearbox already on it. Trying to track down one right now. Anyone happen to know where I could buy one in Canada?
I'll just purchase this and fix the GX120 up for future use. My boy is only 3 so he should get quite a few years out of this build
Once again, thanks a million! Wish I would have signed up 6 months ago lol
Click to expand...

No problem. Trying to source that engine in canada might be a little hard.

EDIT: I did a bit of googling on the engine, but no luck yet
 
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D-MOE

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gran_pann said:
Looks good! How are you going to fit the engine in there?
Click to expand...

Hey Gran Pan,

I'm going to build a plate across from front to back. Have tensioners to slide the engine to tighten the chain. I just purchased a 50cc petrol scooter engine with a 5:1 reduction gearbox on it, hopefully it's in when I get home:).... It's a 2 stroke similar looking to a weed eater. I can't find any specs on it. Would be nice to know the Final RPM to calculate what gearing I'm going to go with. Does anybody have experience with this setup? Maybe I'll start another thread. I'll keep posting pics as I make progress
Thanks for all the help

Donny
 
firemanjim

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I think I know what engine you're talking about. It will pull that jeep just fine, and then some.... I have one on one of my little motorcycles. With a 14" tall tires, it will do an easy 35 and get there pretty quick to boot. I will post some specs for the one I'm talking about. Maybe it's the one you bought....
EDIT the only thing I can find says they make peak power at 7000 rpm and peak torque at 5000rpm..... NOTHING about drive sprocket rpms.... Hmmmm?
 
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