For Piaggio and Gilera 125–180 cm³ 2-stroke engines with an externally mounted clutch shaft, as well as older engines in combination with the separately available HT Rollingnut.
The HT Tuning CNC variator cover was developed for Piaggio and Gilera 125–180 cm³ 2-stroke engines with an externally mounted clutch shaft. In this design, the clutch shaft is mounted in both the transmission cover and the variator cover. The HT engine cover, milled from solid aluminum, serves as the outer bearing point.
However, with the separately available HT rolling groove, the cover can also be used on older engines where the clutch shaft is mounted as standard in the engine block and in the transmission cover. The special nut establishes the connection between the older clutch shaft and the bearing in the externally mounted variator cover.
HT Tuning CNC-machined aluminum externally mounted clutch shaft Rollingnut conversion possible Compatible with Ø 140 mm Ø 110 mm: Note electric starter
In the externally mounted version, one bearing of the clutch shaft is located in the transmission cover and the second bearing in the Variomatik cover. The bearing arrangement typically found in older engines—inside the engine housing itself—is no longer used.
The variator cover is therefore not merely a cover for the variator, clutch, and kickstarter mechanism; it also serves a load-bearing function within the clutch shaft bearing assembly.
Older Piaggio and Gilera engines have a clutch shaft that is mounted in the engine block and the transmission cover. These engines do not come standard with the clutch shaft connection designed for an externally mounted cover.
HT (Heiko Tuning) offers a special rolling nut specifically for this purpose. This nut is used in place of the stock clutch shaft nut and establishes the connection to the bearing in the variator cover. This allows a cover designed for the externally mounted version to be mounted on the older engine block as well.
The Rollingnut accommodates the different designs of the clutch shaft bearing. Space-related limitations with small 110-mm brakes and an existing electric starter remain.
When used with the appropriate HT Rollingnut, the engine cover can also be installed on older engines with a large rear brake. These engines provide the necessary installation space for the cover and electric starter.
In principle, the cover can also be used on older engines with a small Ø 110 mm rear brake. However, the installation space around the electric starter on these engines differs from that of models with a large brake.
If the HT Variomatic cover is to be installed on such an engine, either the electric starter must be removed or the affected area must be modified accordingly. The HT Rollingnut alone does not eliminate this installation restriction.
This restriction applies, among others, to:
Without further modifications, the variator cover can only be used on these engines if the electric starter is removed. If the electric starter is to be retained, appropriate modifications are necessary.
| Engine Model | Accessory | Usage | Note |
|---|---|---|---|
| Motor with externally mounted coupling shaft | No conversion part required | Intended Use | The cover serves as the outer bearing point for the coupling shaft |
| Older motor with a 140 mm brake | HT rolling groove | Compatible | The rolling nut connects to the bearing in the variator cover |
| Older engine with a 110 mm brake | HT Rollingnut | Limited compatibility | Only without an electric starter or after appropriate modifications |
The variator cover is machined entirely from a solid block of aluminum. This allows the bearing housing, mounting points, and contours to be machined with precision.
In an engine with an externally mounted clutch shaft, the exact position of the outer bearing is particularly important. The cover assumes part of the shaft guidance function here and must therefore be designed to be sufficiently rigid and dimensionally stable.
| Manufacturer | HT Tuning / Heiko Tuning |
|---|---|
| Component | Variator Cover / Engine Cover / Kickstarter Cover |
| Main Application | Engines with an externally mounted clutch shaft |
| Older engines | Compatible with the HT Rollingnut (sold separately) |
| Large rear brake | Ø 140 mm |
| Small rear brake | Ø 110 mm; electric starter usable only after modification |
| Material | Aluminum |
| Manufacturing | CNC-milled from solid stock |
| Engine type | Piaggio and Gilera 125–180 cm³ 2-stroke |
| Ventilation openings | Integrated |
| Bearings | Not included |
| Rolling nut | Not included, sold separately |
| Other internal components | Not included |
The openings in the Variomatic cover allow for additional airflow in the area of the Variomatic, clutch, and drive train. With high-performance engines and sporty riding, the additional airflow can help dissipate heat generated in the drive train more quickly.
At the same time, the open milled areas provide a view of parts of the drive train and define the technical design of the HT cover.
Only the CNC-milled Variomatik cover is included. Bearings, the HT rolling groove, kickstarter mechanism, and other internal components are not included.
Before installation, first check which clutch shaft bearing and which rear brake are installed in the engine. For older engines, the HT Rollingnut is also required to connect to the bearing in the variator cover.
The HT Tuning CNC variator cover is designed for Piaggio and Gilera 2-stroke engines with an externally mounted clutch shaft. With the separately available HT rolling groove, the cover can also be used on older engines whose clutch shaft is mounted in the engine block and transmission cover. This also applies to original externally mounted variator covers. For engines with a small Ø 110 mm brake, the restriction remains that the electric starter can only continue to be used after appropriate modifications have been made.
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