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Upgrading the CVT system on a 150cc buggy

This CVT upgrade guide is based on an original work authored by "dewmanity" (Randy) and posted here on www.Buggynews.com. The original photos and text captions used by permission.

Introduction:

This guide will detail how to disassemble, upgrade, and replace elements of the CVT system on a 150cc GY6 motor used in many brands of mini-buggies and scooters.

This guide has instructions on replacing the variator, rollers, clutch, main torque spring, and CVT drive belt.

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Tools:

- Bolt sizes may vary by model of buggy, so have a set of standard and metric sockets and wrenches handy. 17mm nuts are a common size.

- Strap wrench

- Pipe wrench

- Blue Loc-tite

- 1 extra pair of hands (or an assistant!) if doing clutch mods

Optional: An impact wrench will make this process much easier, but is not necessary.

Safety Notice:

Before starting, allow the engine to cool completely. Exhaust and CVT systems achieve very high temperatures from normal operation.

Clutch assemblies are under significant spring pressure. Caution must be taken when removing the final clutch assembly nut.

Part I: Accessing the CVT system

1. The muffler on many 150cc buggies is attached to the CVT cover and must be removed for access to the CVT system. Additionally, the left rear tire may need to be removed on some models.

- If this is the case for your buggy, lift up and stabilize the rear of the buggy with a jack and/or jack stands. Remove the left rear tire, if necessary. See photo for example.

Image 1: Raised buggy with jack stands

2. On the underside of the engine, remove the two exhaust bolts.

Image 2: Exhaust bolts on underside of engine

3. Remove the single bolt that connects the exhaust to the outside of the CVT cover.

- Note: If there is a removable kick-start shaft used as an exhaust mount, remove that as well. You can see the bolt on the side in this photo:

Image 3: CVT cover with exhaust removed.

Note kick-start shaft in middle of cover

4. Remove the bolts around the CVT cover and take the cover off. Some bolts may be different lengths so be sure to keep track of where they came from for reassembly.

5. Take off the CVT cover. Be careful to damage the CVT gasket as little as possible.

Image 4: CVT cover removed. Variator on left, Clutch assembly on right

6. Remove the 17mm nut (size may vary by buggy model) on the variator fan. An impact wrench will make this an easy removal. If you do not have one available, you must secure the fan plate so that the fan does not rotate when loosening the bolt.

Note: Be very careful when removing the variator nut to not damage the variator fan plate or break off any of the "fins".

7. Remove the variator fan plate and drive belt. Set them aside.

Part II: Changing Roller Weights

8. Remove the variator assembly, being extra careful to hold the variator, ramp plate (behind it), and center dowel pin together as one unit. The center dowel pin can be set aside. Holding the variator with the smooth pulley side down, lift off the ramp plate to expose the rollers.

Image 5: Variator assembly, ramp plate, and rollers.

9. Remove the old rollers and set aside.

10. Insert the new rollers into the variator, one to a slot.

- Important Note: If installing sliders, refer to the instructions that came with the sliders for proper orientation.

Image 6: New rollers installed.

11. Place the variator ramp plate back on the variator, matching the three plastic guides around the edge.

12. Holding the variator and ramp plate as one piece, replace the center dowel pin, and put it all back on the shaft, sliding it all the way to the back.

Note: Dr. Pulley variators come with three small washers that can be optionally installed as spacers. In most cases, they are not necessary on buggies.

At this point, if you are only changing the rollers you can begin to reassemble the CVT system. Skip to Part VI for instructions.

Part III: Removing and Opening the Clutch Assembly

13. To access the clutch, remove the clutch bell nut. The size may vary by buggy model, but is commonly 17mm on a 150cc. Again, an impact wrench makes this an easy job, but you can remove with a regular socket it if you restrain the clutch bell from turning.

14. Remove the clutch bell. Examine the inside of the clutch bell. The inside edge should be rough, not smooth like glass. A smooth interior inhibits a good engagement of the clutch with the bell and decreases performance.

- Note: If your clutch bell is purpled and very smooth on the inside edge, it is probably time to replace it.

Image 7: Clutch Bell

Image 8: Inside the Clutch Bell

15. Remove the clutch assembly.

Image 9: Clutch assembly

Image 10: Removed clutch assembly

16. Tighten a strap wrench around the clutch. Use a pipe wrench to loosen the large flat nut holding the assembly together.

- WARNING: The clutch assembly in under spring pressure. When the clutch nut is removed, the clutch assembly will spring apart with force. Use extreme caution when removing this nut, or better yet - have an assistant hold the clutch assembly down as the nut is removed.

Image 11: Strap wrench and pipe wrench used to remove nut

Image 12: Clutch assembly after nut removal

Part IV: Changing the Clutch Main Torque Spring

17: Lift the clutch off of the spring assembly and set aside.

18. Lift the old spring off the clutch pulley plates, and remove the spring guide from the end of the spring.

19. Set the new spring onto the clutch pulley plates, and insert the spring guide snugly into the open end.

Image 13: New spring with spring guide

Part V: Installing a New Clutch

(or reinstalling the original clutch)

20. Place the clutch on top of the main spring and compress the assembly. The new spring is much stiffer than the old one and will be a lot harder to compress. You will need to align the small hole in the center of the clutch with the shaft on the clutch pulley plates. Reattach the flat clutch nut.

- Note: This process is much easier with a 2nd pair of hands, so an assistant may be necessary.

- Note: Use of blue Loc-tite on these nuts is recommended. It is vitally important that they do not come loose during operation.

Image 14: Clutch

Image 15: Clutch on compressed spring.

Image 16: Completed clutch assembly

21. Slide the clutch assembly onto the splined shaft. Replace the clutch bell and tighten the 17mm nut.

- Note: Use of blue Loc-tite on these nuts is recommended. It is vitally important that they do not come loose during operation.

Image 17: Replaced clutch assembly

Part VI: Replacing the CVT belt and putting it all back together

22. Replace the CVT belt over the clutch side pulley plates, then stretch it over the shaft on the variator side onto the variator dowel pin.

- Note: You may have to pry apart the clutch pulley plates to get the belt enough slack to get onto the variator dowel pin. This can be a difficult process and care must be taken to not damage the pulley plates or the belt.

Image 18: Belt replaced on variator side

23. Replace the variator fan, and tighten the nut on the variator side

- Note: Use of blue Loc-tite on these nuts is recommended. It is vitally important that they do not come loose during operation.

24. Once the variator fan plate and clutch bell are securely attached and bolted down, rotate the CVT system to settle the belt into position. This can be done by manually rotating the pulleys..

Image 19: CVT system

25. Replace the CVT cover and all bolts in their proper location.

Image 20: CVT cover reattached

26. Reattach the exhaust by reversing the steps at the start of this guide, and put the left rear tire on if you had to remove it. Remove the jack stands and place the buggy back onto level ground.

27. Start the buggy, let it idle and listen for any abnormal noises from the CVT area. Rev the motor a few times, listening for problems.

28. If all sounds well, take it out for a slower speed drive. If the buggy bogs or does not have smooth acceleration, the rollers may have shifted when putting the variator and ramp plate assembly back on. Stop driving and follow the steps to disassemble and verify correct installation.

29. Have fun with your newly upgraded CVT system!

This CVT upgrade guide is based on an original work authored by "dewmanity" (Randy) and posted here on www.Buggynews.com. The original photos and text captions used by permission.

Copyright 2008 Buggy Parts NW

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