Newbie question: Baja Reaction Sprocket help!

[jameslbarry]

I recently brought home a Baja Reaction 150cc.
The original engine was a GY6 150cc. (I just got a GY6 180cc to replace it)
The go Kart did not come with any sprockets. I figure the best place to start is to find a sprocket for the rear axle...

What should I be looking for?
I've heard there are sprockets for dual row, single row, different sizes of chains (both in link size and length)...
(I see numbers like #420, #428, #50... but I'm not sure what they mean. lol )
A big variety of sizes (tooth count) which I understand will determine the gearing (which I believe also involves the gear on the engine and also the wheel size)

Any advice/education is appreciated. (keep in mind, my goal is not crazy performance... to understand my priorities: I'll be happy if it goes 20mph, I'll be sad if it can't climb a medium sized hill)
My biggest question is if there is a sprocket out there that I can even get onto my axle? It looks like I will need to completely remove the axle to make it happen... anyone have a Baja Reaction who has carnal knowledge?

I'll attach some pics to show the setup.

 

[jameslbarry]

Pics…

 

[Hellion]

What was the tooth count on the original axle sprocket? You seem easy to please so starting at the original specs could be adequate for you.

Look for single row chain, this is not some static industrial machinery, it's a kart (although I'd like to see double row chain on motorcycles and stuff, that would be neat).

 

[Master Hack]

Chain 101:
the numbers 35 - 40 - 420 refers to the pitch or dimension between the pins Thats the links. 35 = .375(3/8) 4xx = .500(1/2) 5xx = .625(5/8)
there are different widths and roller diameters for every pitch. Sorry ya asked?
good info here:

Roller Chain, Engineered Class Chain & Sprockets | Nitro Chain

www.nitrochain.com

 

[Master Hack]

Measure the bolt circle diameter of the hub and one of the kart supply houses will have watcha need. Ya need the chain pitch on the engine (if ya have one) .
between these holes will be a common size for sprockets. They even have split sprockets if yer too lazy to drop the axle.

 

[jameslbarry]

What was the tooth count on the original axle sprocket? You seem easy to please so starting at the original specs could be adequate for you.

Look for single row chain, this is not some static industrial machinery, it's a kart (although I'd like to see double row chain on motorcycles and stuff, that would be neat).

Unfortunately I got it as an incomplete project, so I don’t have the original engine (i still near to order the kit that includes the carb, coil, cdi, etc…). and the sprocket was missing. I downloaded the owner’s manual for this kart, but it doesn’t specify the sprocket or gear ratio.

 

[panchothedog]

Does your engine have a drive sprocket on it? If so ask the vendor what pitch it is.
If it doesn't, and just has an output shaft, then just keep everything ( drive and axle sprocket and chain ) the same. #420 or #428 ( and they are compatible with each other ) is by far the most popular size used on off road yard karts like yours, an is available from all of the kart supply shops.

 

[Edwin Spangler]

Im looking at that engine. It has a kick starter and shift lever. Is that going to work on the kart? Looks like an engine for a mini jeep.

 

[Hellion]

Unfortunately I got it as an incomplete project, so I don’t have the original engine (i still near to order the kit that includes the carb, coil, cdi, etc…). and the sprocket was missing. I downloaded the owner’s manual for this kart, but it doesn’t specify the sprocket or gear ratio.

Oh, right. Our talented team of experts can find that information in 5 minutes or less. Great project though, getting to do it your way with some customization, etc.

 

[jameslbarry]

Does your engine have a drive sprocket on it? If so ask the vendor what pitch it is.
If it doesn't, and just has an output shaft, then just keep everything ( drive and axle sprocket and chain ) the same. #420 or #428 ( and they are compatible with each other ) is by far the most popular size used on off road yard karts like yours, an is available from all of the kart supply shops.

Unfortunately, The Kart didn't have the original engine when I got it, so the GY6 that I just got is brand new and I still need to get a drive sprocket for it, as well. I figured that I would want to ensure the sprockets are compatible. Now just need to figure out the teeth count. It's too bad that info isn't in the owner's manual.
I was hoping someone out there had the same kart (or something similar) and could just share what they were using.

 

[jameslbarry]

Im looking at that engine. It has a kick starter and shift lever. Is that going to work on the kart? Looks like an engine for a mini jeep.

Good observation!
I don't think the position of the kick start will allow it to work once the engine is bolted in, but the engine has an electric start that I will wire to an ignition key near the steering wheel.

The shift lever is for the integrated reverse. There is a shift lever between the seats that is supposed to be for the reverse. I hope to be able to somehow connect that lever to the shift point on the engine. With enough creativity I am optimistic it can be possible.
Worst-case scenario, we just reach back to move the lever to engage reverse.

 

[ezcome-ezgo]

Remain creative and optimistic, it's really for the best.

 

[jameslbarry]

Measure the bolt circle diameter of the hub and one of the kart supply houses will have watcha need. Ya need the chain pitch on the engine (if ya have one) .
between these holes will be a common size for sprockets. They even have split sprockets if yer too lazy to drop the axle.
View attachment 157236

There's a lazy part of me that wants to get out of dropping the axle, but it looks pretty straight forward to do. In about 5 minutes I removed the hub on one side. I figure I'll pull the whole axle. While I'm at it I can do a more thorough inspection of the brakes and clean everything up before putting it all back together.

The bolt spacing for that sprocket looks to be 4 x 3 and 3/16" (The caliper says 3.210")

 

[jameslbarry]

Chain 101:
the numbers 35 - 40 - 420 refers to the pitch or dimension between the pins Thats the links. 35 = .375(3/8) 4xx = .500(1/2) 5xx = .625(5/8)
there are different widths and roller diameters for every pitch. Sorry ya asked?
good info here:

Roller Chain, Engineered Class Chain & Sprockets | Nitro Chain

www.nitrochain.com

I'm not sorry for asking at all! Thank you for this information!

It sounds like the 4xx pitch is probably the most common for these karts.

It looks like I am close to knowing what I need to get:
4xxx pitch
Drive sprocket compatible with a GY6
Axle Sprocket has bolt pattern of 4 x 3 and 3/16" (3.210"-ish), and a bore of at least 3.837".

Just need to know what gear ration/tooth count for each, and I'll get these ordered.

I will also need a chain that is 4xx pitch, but I might wait to get that later. The original engine mounts were cut out, so I'll fab up some new mounts that are pretty close to the factory position. I think there was originally a chain tensioner system on the original setup that may have adjusted the engine position, thereby adjusting chain tension. I need to learn more about that so I can replicate it. That would be easier than no tensioner at all.

 

[ezcome-ezgo]

Looks like those sprockets are 428 pitch, most available in 19 tooth.

Amazon.com: 428 Chain 19 Tooth Front Output Sprocket Wheel for Gy6 150cc ATV Quad Go-Kart Taotao : Automotive

Buy 428 Chain 19 Tooth Front Output Sprocket Wheel for Gy6 150cc ATV Quad Go-Kart Taotao: Sprockets - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

 

[Whitetrashrocker]

Flip your tape measure to the metric side.

 

[jameslbarry]

Looks like those sprockets are 428 pitch, most available in 19 tooth.

Amazon.com: 428 Chain 19 Tooth Front Output Sprocket Wheel for Gy6 150cc ATV Quad Go-Kart Taotao : Automotive

Buy 428 Chain 19 Tooth Front Output Sprocket Wheel for Gy6 150cc ATV Quad Go-Kart Taotao: Sprockets - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

I just measured the output shaft on the GY6. it is a 1" shaft/ 24 spline.

In 428 pitch I do see some that are 19T.
I've read that a common/universal gearing for karts is 6:1... with a 19T drive gear, I would need a HUGE axle sprocket (114T) to get that gearing (rear tires are 22")

Although, there seems to be a greater variety of sizes of front chain sprockets if I look at 530 pitch... Going this route, I could possibly get a 13T drive sprocket and the axles sprocket would need to be 72T (assuming the 6:1 ratio is what is best for my needs)

 

[Hellion]

Probably an 80mm bolt circle as with all Baja parts.

Look for single row chain, this is not some static industrial machinery, it's a kart

Well this statement was in error, the original driven sprocket is a double sprocket driven by a double row chain. Fancy!

For the 150cc version:
BR150S-297 SPROCKET, DRIVEN
BR150S-304 CHAIN, 520 / 24 LINKS DOUBLE CHAIN

250cc version:
BR250-148 SPROCKET, DRIVEN 33
BR250-153 DRIVE CHAIN 50

Baja Motorsports

TTI Consumer Safety Notices

www.bajamotorsports.com

Is 33 the teeth count?

 

[Edwin Spangler]

Good observation!
I don't think the position of the kick start will allow it to work once the engine is bolted in, but the engine has an electric start that I will wire to an ignition key near the steering wheel.

The shift lever is for the integrated reverse. There is a shift lever between the seats that is supposed to be for the reverse. I hope to be able to somehow connect that lever to the shift point on the engine. With enough creativity I am optimistic it can be possible.
Worst-case scenario, we just reach back to move the lever to engage reverse.

There is a push/pull adapter that usually comes on the transmission of these engines. Im sure its a simple swap.

The kick-start, I would be tempted to make a remote starter for it. Or whatever they call it, the handheld starter the minibike guys use.

 

[Master Hack]

BR150S-304 CHAIN, 520 / 24 LINKS DOUBLE CHAIN

I find it difficult to believe they used double row 520 chain. Crortch rockets use 520 single row for the most part.
520 aint real cheap, meaning they ain't using anything that costly.
Maybe something got lost in the translation?