GY6 Tech Article Summary:
Want to know exactly what our transmission modifications do? Look inside for a detailed explanation on each.

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Upgrades: Transmission Modifications
Written by Travis @ BD-ORB
This article has been viewed 4767 times.
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Transmission Upgrades
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The GY6 CVT transmission is composed of several key components: variator, roller weights, clutch, and the contra spring. There are also clutch engagement springs & different drive belts but that wont be covered here just yet.

Roller Weights – Changing out the rollers is undoubtedly the best bang-for-the-buck upgrade there is for your buggy. Roller weights provide the up shifting forces for the CVT transmission by flinging outwards within the variator in varying stages of engine RPM. Roller weight tuning is a matter of preference and riding terrain. A lighter weight will fling outward slower than a heavier weight, slowing the up shift process. The stock 14.5g weights are rather heavy and up shift very fast in the RPM cycle, resulting in hindered acceleration and low-end grunt. These are our notes regarding tuning and roller weights.

9 gram rollers - Unbeatable low-end grunt. However, this light weight will reduce top speed by 2-3 mph, and also kills acceleration.
Best for hill climbing, mud, sand, water and other loose terrain.

10 gram rollers - Great for overall performance. Spins most stock tires from a standstill with other supporting CVT mods. Good sustainable low-end power and optimal acceleration on hard-packed terrain. Does not reduce top-speed.
Best for pavement racing.

12 gram rollers - Reduced wheel spin at takeoff relative to 10 gram rollers, and smooths out acceleration. Terrible low-end torque when compared to 9 and 10 gram weights. Otherwise they function the same as 10 gram weights.
Best for loose terrain racing.

I recommend trying different roller weights to see what you like best. We carry 8 - 13 gram roller weights in the BD Online Store.

1500RPM "Power" Spring - The power spring provides the down shifting forces in a CVT transmission by working against the roller weights. CVT tuning is all about balancing the roller weights with a proper contra spring. The 1500RPM spring increases the tension on the belt and rollers. This delays the transmission from up shifting too soon and also reduces belt slippage. The 1500RPM spring itself increases and smooths out acceleration, low-end grunt, and maximizes back shift. "back shift" is the delay time it takes the transmission to down shift when engine RPMs drop. This is best visualized when thinking about coming in and out of a tight turn. Slowing for the turn the RPMs drop, you then clear the turn and apply full throttle. This is where back shift plays in -- you want the transmission to down shift to the proper lower gearing ratio as soon as possible through the turn so the CVT won't be stuck in an up shifted state when throttle is reapplied coming out of the turn.
The 1500RPM spring can be found in the BD Online Store.

High Stall Clutch - High-stall clutches engage at higher engine RPM, with more force than the standard clutch. This helps keep the small 150cc engine nearer to its power band during demanding situations where the power train is loaded to the point of clutch slippage. These situations can be during steep hill climbing, towing, or when pushing the front end up over large obstacles. High engagement clutches provide better launch from a standstill as well.

115mm Teflon Variator – The teflon variator are 12mm larger diameter than the stock unit. Stock is 103mm. The Teflon coated ramp plate the ensures smooth operation and increased roller weight life. The 115mm and variators are designed with steeper roller ramp angles for an improved acceleration curve. The revised roller ramp angles delay the CVT up shifting process until a specific RPM is reached, which I believe to be around 5500RPM. This keeps you well within good power range even at low speeds, and optimizes acceleration RPM when flooring it.

Transmission summary
If you are looking for-- LOW END GRUNT and don't mind a slight decrease in top speed you will want to take a look at this setup:
9g Rollers, High Stall Clutch, 115mm variator, 1500RPM Spring

For best OVERALL POWER OR TOP SPEED you will want this transmission setup:
10g OR 12g Rollers, High Stall Clutch, 115mm Variator, 1500RPM Spring

View more Buggy Depot GY6 Tech Center articles

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