Rear sprocket sizes on mini Beast and Rebel T1

[hhiker42]

I bought a Mini Beast for my son (6 years old) and a Rebel T1 for my daughter (11 years old). We went for a ride and my daughter's couldn't climb anything. So I looked closer at the sprockets (counted teeth). And the Rebel has a smaller rear sprocket and larger front sprocket.

Since it is easier to replace the rear sprocket (don't have to worry about spline lining up or having a clip) I did some research and found the following matches. I figured I would share the results.

Mini Beast (currently front 420#14 and rear 420#37 gives 2.64):
http://www.jtsprockets.com/61.0.html?&L=0
The JTR801.41 gives 2.93
The JTR801.42 gives 3.00
The JTR801.43 gives 3.07
The JTR801.44 gives 3.14
The JTR801.45 gives 3.21
The JTR801.46 gives 3.28

Rebel T1 (currently front 428#15 and rear 428#32 gives 2.13):
http://www.jtsprockets.com/61.0.html?&L=0
The JTR802.44 gives 2.93
The JTR802.45 gives 3.00
The JTR802.46 gives 3.07
The JTR802.47 gives 3.14
The JTR802.48 gives 3.21
The JTR802.49 gives 3.28

What gear ratio would be best for off road use?

To help complete this thread, does anyone know corresponding part sizes for the front sprockets?

Thanks, Noah

[rotax583]

13-40 for the beast and 42 rear for the rebel.makes a bug difference and still gives you a bit top end.and can tell exactly what oem sprockets that fit when I go to shop tomorow.

[hhiker42]

Thanks for the research help.
A 13-40 for the mini beast would give 3.08
This is almost the same as a 14-43 which gives 3.07

My understanding is that is easier on the chain if the front sprocket is not too small. Also, by just upgrading the back sprocket I only have to buy one sprocket instead of two. Is this bad thinking? Would it be better to change both sprockets and keep the rear sprocket a little smaller?

Thanks again,
Noah

[rotax583]

43 is getting a little big.it will be pretty close to the guard if its still on and if not you lose ground clearence.and for the 13 theres no problem,we ran one for a full summer and had no problems.

[hhiker42]

Very good point.
I didn't think about clearance and the chain guard. So it looks like I should change the front sprocket too.
By chance do you know the number that would fit the front sprocket?

I read somewhere else that the JTF253 will fit the miniBeast (it is 420) but I haven't measured the front to confirm. I will measure later today.

But I haven't found anything for the front sprocket of the Rebel T1, yet.

Thanks,
Noah

[Weldangrind]

To respond to your front sprocket question, don't go any smaller than 12 teeth in the front for greater longevity. The chain has a hard time articulating around anything smaller.

[rotax583]

front t1 13 tooth jtf 277 from trx 90
rear t1 40 tooth sprocket jtr 802 from 76-82 kawasaki ke100 dirt bike

mini beast rear jtf 801 from 84-85 lt-50 suzuki
mini beast front jtf 253 from 82 cr 80( or atc70)


ther you go!!!! now if anyone knows what fits on a maxam 50cc atv,let me know.thanks

[hhiker42]

To find out what fits on a maxam 50cc atv could you try Bike Alert?

http://www.bikealert.com/3.0.html

[hhiker42]

The parts arrived and are installed. The following is what I ended up getting and how they fit.


Mini Beast
Front Sprocket: I tried getting the above mentioned sizes (or the JTF253) but my parts guy couldn't get them, so we I got the JTF252 (13 tooth) and it fits perfect. (it also fits the shaft on the Rebel T1 perfectly as well but is 420 pitch for the chain).
The MotoVan part number for this was 324-9105 (around $10)

Rear Sprocket: I am pretty sure the JTR801 would have fit, but I couldn't get it in 39 or 40 teeth and 41 teeth was going to cost too much ($30). Since it already has 37 teeth on the rear I decided to leave it be. Then I didn't have to buy a new chain either.


Rebel T1
Front Sprocket: I best we could find in the 428 pitch was the JTF273 with 13 teeth. It almost fits perfectly but is 1mm smaller on the inside hole. So I had to take a small flat file and shave 0.5mm off each spline on the sprocket. Easy.
The MotoVan part number for this was 324-4113 (around $11)

Rear Sprocket: I bought the JTR804 with 40 teeth. Fits perfectly. I could have gone a bit (1-2cm) larger but I am happy with this combination. My daughter can actually climb hills on it now.
The MotVan part number for this was 324-9678 (around $22)

I also got a new 428 chain. (around $22)

Note: I had to drill the holes on the clip that holds the front sprockets in place a tiny bit (1/16th of an inch) larger. This was easy, but be sure to use a vice or good pliers to hold the clip while you drill it.

Noah

[rotax583]

your parts guy should have looked with a different supplier.afam sprockets have a great selection.if you ever want any more sprokets let me know.im a parts supplier and get get those sprockets to you for a very good price...even with shipping.