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Razor Dune Buggy upgrade question

I've read most of what is on this forum but want to clarify 2 things. 1. If I add a 3rd 12v battery to the dune buggy leaving all else stock do I need to change the throttle or can it handle the 36v? 2. If I install the 36v 650 watt motor and controller from the mx650 dirt rocket and a 3rd battery I should not expect a speed increase over the original 24v 350watt set up on 24v? I would guess much more torque of not more speed. Please confirm or tell me if I've misunderstood. Thanks Carl
The stock Dune Buggy throttle can handle 36 Volts, however, its battery indicator will always show full. The original 24 Volt motor and controller are the parts that tend to overheat and burn out when running at 36 Volts.

If a 36 Volt 650 Watt motor and controller from an MX650 are installed on the Dune Buggy the top speed will be around the same and the torque will be greatly increased if the jackshaft is continued to be used. If the jackshaft is removed and the chain goes directly from the motor sprocket to the axle sprocket then the top speed will be significantly increased though.
Excellent information thanks! What I need is a larger sprocket for the 650 motor to pick up some speed. Currently I have a 13 tooth sprocket. I bought one from you when I upgraded the mx650 to 1800 watts 48v brushless a while back. Will need to see if you have anything larger than 13 tooth for that motor. Thanks! May also need a couple master lengths to extend the chain. Pretty tight.
Ran it today 36v, with razor 650 motor and controller. On the motor I have a 13 tooth sprocket and can't recall if that is stick or if 11 tooth would have been stick on the mx650 motor. We picked up about 2 or tips 3 mph and as you said torque is significantly more. It will now go straight up a hill over and over after 20 minutes of general riding that it could not do at all before. Now I need a larger sprocket for the motor or the other small one in the system or to make smaller one of the two large sprockets. Not sure if there are alternatives to the other 3 sprockets.
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An 11 tooth sprocket is stock on the Razor MX650 motor.

A 13 tooth sprocket is the largest size made for that motor, and the jackshaft and axle sprockets are made specifically for the Dune Buggy so off the shelf replacements in different sizes are not available.

There are a couple of options to increase the gear ratio that both require drilling and or machining sprockets that mount with set screws to fit the motor or axle.

Our 14, 15, or 16 tooth sprockets for #25 chain with 8mm bore could be drilled or machined to have a 12mm bore that would fit on the shaft of the motor behind where the original sprocket is mounted. Since these sprockets are secured to the motor shaft with set screws they would not be attached as well as the original sprocket so to solve that problem dimples could be drilled into the motor shaft for the set screws to seat into, or a hole could be drilled through the sprocket and motor shaft for a roll pin to go through.

Another option would be to use a sprocket such as our SPR-2524 24 tooth sprocket with 3/8" bore for #25 chain to replace the original 32 tooth axle sprocket. This would require drilling or machining the sprockets 3/8" bore to 20mm and machining a keyway into the sprocket.
Looking for eaier option to trade torque for speed I've looked at getting larger tires. Axle seems to be 20mm which is just a hair larger than 3/4". I've order a 3/4 go kart hub to see if it will go on with persuasion. If that works I can bump up these 7.5" tires to 9, 10 or 12" tires easily. 12" would give me about 60% more speed. Too bad nobody sells a wheel with 20mm hub
That sounds like a great idea. Please let us know how it goes after you get the hub.
I used the long threaded 1/4" threaded rods with clear tubing covering to protect motor and give grip as someone else here mentioned. I was able to bend the arm that held the controller in place and use it to attach to back of motor. 1 addtional battery of same size for nicely with minor mod to battery tray. Also added a watt, current, AH remaining, % charge, volt meter. It allows to see current flowing in for charging as well as out when boys are riding. With my 13 tooth motor sprocket I'm getting 7.25 turns of motor for each full turn of wheels. This is identical to stock mx650 with 11 tooth motor sprocket and 80 tooth wheel sprocket. If friction losses were the same then the Dune Buggy would have identical speed and torque (hill climb) as the mx 650 if the dune buggy had same diameter wheels. They are roughly 14.5-15". I plan to test 12" go kart wheels and go from there. Hub will be here next week. Likely need to drill out hub to 51/64" or 13/16". As it is the torque snaps the head back even trying to slowly add throttle.
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I've received the hub and am waiting on delivery of a 51/64" drill bit.  Meantime I've found a great deal on 14.5" wheels.  Only issue is they have 1" hub bore and we need 20mm for the Dune Buggy axle.  I found a sleeve that will fill the gap but can only find it in the UK and though it is only $5 they want $35 shipping for one and an extra $14 for each additional for a total of $59 for just two.  Here is a link to what I'm looking for though it is 25mm outside diameter and I'd prefer 25.4mm to match one inch.  Please let me know if any one can find similar for less.  1" (or 25.4mm) OD, 20mm ID and 85mm long would be ideal but I can use several to come up with 85mm if you find something shorter and could cut one down to 85mm if you find longer.

https://www.ebay.com/itm/272628304885#shpCntId



The 1" OD x 0.782" ID steel tubing at this link is sold by the inch and is only 43 cents per inch: http://www.speedymetals.com/pc-3496-8242-1-od-x-109-wall-dom-steel-tube.aspx

This tubes 0.782" ID is 19.8628mm. According to the Power Racing Series blog at this link https://www.fictiv.com/blog/posts/power-racing-series-build-part-2 the Razor Dune Buggy axle is 19.85mm OD.

Awesome, super helpful.  I was looking at ordering a batch from China and waiting forever.  I've placed an order for 4 of these that you've mentioned.  Should work great.  I plan to cut a 5mm strip out full length or at least 3/4 length for the keyway so if it's a little tight around the 20mm axle then it will be able to expand somewhat.  Wheels are also on the way.

With this adapter ANY rim with a 1" hub will work so long as it's not too wide.  I may send back the 3/4" hub I bought and the 51/64" drill bit I've not yet received.

THANK YOU!

Here's the look with 12.5 inch tires on rear 10 inch front. Could still be a couple weeks before front bushings arrive for front rims. If anyone knows of 10mm id x 16mm od bushings or sleeves that may be stocked somewhere that would speed things up. Need about 60mm or 2 inches long unless they are flanges then 12mm might do it. 14.5 inch rears arrive next Friday.
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I received the sleeves / tube from speedy metals. Axle is 0.7825. Sleeve inner diam is 0.7750 so it will not slide on. Still works great for me as I intended to cut a key way so cut it full length in the tube and it allowed tube to expand enough to be tapped on and still nice close fit to 1 inch rim hub. Extended keyway in axle out to the end as it's original placement allowed it to fall through the key way of the new sleeve and it into the rim. New longer key 1.75 inch long is jb welded to the sleeve and the sleeve to the rim hub. Axle and axle keyway oiled so key stays with the wheel when removed otherwise the spacers that keep the rim out from cart frame and thus tire away from frame would not be removable. Need to be removable so I can try different rims/tires later
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