You can find out without taking the motor apart. This is typically part of the specs released on bikes, the more detailed specs usually have these numbers, the gear ratios, primary ratios and secondary drive ratios.
I have sometimes been able to search on bikes online and find the information. If not though, it may be in your manual if you have one or get one. You can also call a place like Halls Cycles and ask them if they have that information. Just tell them you want the information to work on what sprockets you need to gear your bike so they may think you will order something later if you think they may not try to help.
The 1983 Sand Spider was setup to race desert so it's very fast and this gearing carried forward for enduro in the following models. They even made it slightly taller in the later years with 2.28 1st gear (from 2.36) and 1.96 Primary Ratio (from 2.13).
Your options for gearing down your bike are only to change the diameter of your rear tire or adjust the secondary drive.
Secondary Drive:
Cons:
1. The range of which you can gear is limited by the sprockets produced.
2. Different size sprockets may wear faster or cause more slack in the chain.
3. Perhaps at your comfortable/usual speed the drive shaft may be spinning faster than it would need to be if internal gearing was different.
Pros:
1. Easy to change.
Changing Rear Tire Diameter:
Cons:
1. Just like Secondary Drive mods this will gear your entire transmission.
2. Limited to available sizes, essentially 17", 18" or 19".
3. Most painful to change, not easily fitted to determine if you like it.
Pros:
1. Able to perform gearing without modifying the sprockets
2. May produce larger effect as opposed to using the equivlent in sprockets.
Primary Drive:
Cons:
1. Required to be performed at manufacturing, can't be done by you unless it's being manufactured.
2. Adjusts the entire transmission, all gears.
Pros:
1. Ability to reduce the speed of the output shaft for a particular speed.
2. Adjusts the range at which the secondary drive needs to be adjusted.
I.E. if this it TOO HIGH, it forces your secondary drive ratio too high in the spectrum. If it's at a comfortable medium, it allows more flexible secondary drive tuning up or down.
1st Gear (Individual Gears):
Cons:
1. Required to be performed at manufacturing, can't be done by you unless you can buy other gears or find gears from a different bike which work.
2. Must be paired smoothly with the next gear, cannot be too spaced or you will not have good pickup when shifting gears.
Pros:
1. Can adjust single gear ratios to allow for a best mix of tall and low gears to your suiting.
Primary: 66 / 31 = 2.13
1st Gear: 33 / 14 = 2.36 (5.03 Output)
2nd Gear: 29 / 17 = 1.71 (3.64 Output)
Changed Rear: 58 / 12 = 4.83
Stock: 48 / 16 = 3.0
Changed Rear Total: 24.29 Ratio
Stock Total: 10.92 Ratio
Stock Top Speed: ~115 MPH
My Top Speed: ~60 MPH (I have a Speedometer, matches my estimates)
1st Gear Top Speed Mine: ~20 MPH (I have a Speedometer, matches myestimates)
1st Gear STock Top Speed: ~35 MPH
My gearing down works out good for 1st gear, but once you get past second the gears are way too close. Even though the bike still does 60MPH, the top end gears need to be spaced out more for this Maico to really stretch. I still never can hit 5th gear wide open where I ride, so it's not too bad, however on the roads I can tell that the higher gears are too close. The lower 1st is OK, second could be a little bit higher and then 3rd to 5th should be the same. With a 58 tooth on the back and 12 ont he front
though, if I ever go to terrian I want to increase my speed I can easily pop out the front sprocket on the spot and put in a 15 or 14, it's just held in by a circlip, makes for easy maintaince.
