BGM PRO shaft sealing rings made of high-quality and ethanol-resistant (E10) FKM/Viton®*
CORRECT HEIGHT (20x62x7MMM INSTALLATION 20x62x6.5MM)
The BGM PRO shaft seal on the coupling side has a height of 7mm instead of the 6.5mm normally used by other manufacturers. This means that the BGM PRO shaft sealing ring is based on the original old Piaggio design. Anyone who disassembles an old original motor will notice that a 7mm oil seal has been used on the clutch side.
FLOATING Crankshaft
The crankshaft bearings of the old engines are `floating`. This means that the bearing is not fixed and can be moved axially (sideways) in the motor housing. This happens e.g. under load due to the axial force of the helical toothed primary drive. If the crankshaft shifts too much, this can have an effect on the ignition as well as on the operation of the clutch.
STOPLIMITATION
In these engines, therefore, only the shaft sealing rings serve as lateral stop limiters. The height of the shaft seals thus determines the amount of `air` between the bearings and the shaft seals themselves. The tolerances in the old motors are so large (e.g. due to motor sealing paper with greater thickness than at that time) that even with the 7mm height there is still more than enough distance. The bearings therefore run without preload.
WHY FKM/VITON®
The material FKM (fluorocarbon rubber) is extremely resistant to heat, friction and fuel/ethanol. Current super fuel in Germany already contains up to 5% ethanol per se. In other countries the ethanol/alcohol content is significantly higher. Conventional shaft seals can swell or soften on contact with fuels containing ethanol. The BGM PRO FKM/Viton® rotary shaft seals offer perfect protection against this. In addition, Viton is twice as temperature resistant as conventional (blue) NBR shaft seals, has very good gas impermeability and is also very resistant to ageing.
FITFOR
An engine equipped with BGM PRO FKM/Viton® shaft seals can therefore also be used without problems in engines that run on E10 fuel (10% alcohol content).
The high-quality brown Viton®* sealing material is permanently resistant to alcohol and is also suitable for engines with high temperature loads and high speeds.
BGM PRO FKM/Viton® shaft seals are therefore suitable for all engines, whether original or tuned high-performance engines.
For reasons of environmental protection and in favour of a maximum flexibility of the sealing lip, we deliberately do not apply any additional PTFE/Teflon®* to the sealing lip.
ADVANTAGES BGM PRO
The BGM PRO shaft sealing rings offer double sealing as an additional feature. All shaft sealing rings that seal to the atmosphere have a so-called dust lip. This is positioned before the actual sealing lip and keeps dust, dirt and moisture away. This further increases the very good stability.
CONCLUSION
The BGM PRO rotary shaft seal set improves the installation clearance and offers an extremely long service life due to the excellent materials FKM/Viton® combined with perfect fuel compatibility as it is even E10 resistant. Fits without modifications in all Vespa largeframe engines with two equally sized crankshaft bearing types.
*Viton®/Teflon® are registered trademarks of DuPont Dow Elastomers
