As with any modification, be sure the rider is skilled and strong enough for the changes before altering the quad’s performance. Many youth quads have integrated safety features that are used to control their speeds and keep young riders safe. KYMCO two-stroke has three stages to boost its speed.
1. The first stage is to turn the throttle stop screw all the way out. The result is a top speed of around 10 mph.
2. Stage two, is to modify the clutch bushing on the Lil’ ’Goose’s primary fixed sheave.
3. The third and final stage on this ring-dinger is to clip the looped green wire on the CDI box.
With these three changes, the Mongoose 50 two-stroke should be able to achieve a max speed of around 30 mph!
1. Remove the entire left side floorboard.
2. Loosen all the bolts and remove the CVT housing.
3. With clutch cover removed, you should see the exposed primary and secondary sheaves. The front one is the primary fixed sheave and the rear is the secondary unit. This is a good time to inspect the cover for excess belt dust and excessive wear. Set it aside for now. It’s also smart to make sure the starter gear below the primary sheave is fully seated and in place. It can come loose while removing the cover.
4. Use an impact wrench to remove the nut securing the front pulley or primary sheave. Hold the sheave with your hand and pull the trigger.
5. Remove the the primary fixed sheave.
6. Remove the drive belt and clutch boss from the front crankshaft while holding the primary fixed sheave in place.
7. Since you’re inside the clutch, you should inspect the sliding sheave, its weight rollers, the belt and cam plate. Use caution when removing the sheave, because the roller weights will roll and could fall out. Inspect the roller weights for any flat spots.
8. With the bushing removed, you’ll be able to see the lip more clearly. You now can do three things: order a new bushing from the aftermarket, insert one from a KYMCO Super 9 scooter or machine the lip off the stocker.
9. Once you’ve decided which way to go, reinsert the new bushing. However, if you machined off the lip yourself, insert the machined side onto the crank first to ensure any imperfections are hidden within the assembly and don’t make contact with the belt. There should be no reason to force the bushing back on the crank and it should “seat” like the stock piece.
10. Reattach the belt to the crank.
11. Put on, the primary fixed sheave being careful to align it properly. Next, put on the washer and nut. Tighten the nut by hand until you seat both clutch halves. Then tighten the nut with the impact wrench. Return the cover — being careful to align the rubber gasket and tighten it to KYMCO specifications. Then, reattach the floorboard.
12. We think 20 mph is good for most youth riders. However, if your kid is extra special, go ahead and clip the greenish wire on the CDI box, located under the seat. It’s a small wire all by itself coming out of the CDI and quickly “looping” back into the box.