The RUNNER input shaft assembly: It possesses shorter 3rd and 4th gears that do not require the use of differently sized gear cogs on the output shaft. The second simple and effective step into the world of gear box ratio tuning.
The DRT RUNNNER input shaft assembly has gear cogs with 20, 17, 14 and 10 cog teeth respectively which makes the 3rd and 4th gear ratios shorter. The OE PIAGGIO 3rd and 4th gear cogs on the output shaft can still be used in combination with this conversion kit. This input shaft assembly conversion enables uninterrupted acceleration through all gear changes and is especially suited for motors with a cubic capacity of between 100 and 130cc. It is very good in combination with the 1st gear for the output shaft with 55 teeth produced by DRT (Art.-No. 40431710) and the very short 2nd gear, also by DRT, with 55 teeth. Performance orientated motor setups can also benefit from the use of the DRT 2nd gear cog with 52 teeth, the DRT 1st gear cog with 54 teeth and the DRT 3rd gear cog with 49 teeth. The 4th gear cog which is an OE PIAGGIO item with 50 teeth does not need to be changed.
The input shaft assenbly RUNNER RACING is produced for SIP on special request. It is made of best german steel. Difficult to modify, very tough and needs a special heat treatment i production. This steel is the best material DRT gets to make gear kits.
For High-End engines >25PS DRT strongly recommends the use of the RSP series.
DRT has the following input shaft gear ratio recommendations:
POLINI 100cc, 2.88 = 24/69 or 2.86 = 21/60 gear cog tooth combination
POLINI 130cc, 2.55 = 27/69 or 2.61 = 23/60 gear cog tooth combination
QUATTRINI M1/M1L/PARMAKIT, 2.73 = 22/60 or 2.76 = 25/69 gear cog tooth combination
Conclusion: Shorter 3rd and 4th gear ratios without having to change the output shaft gear cogs. A simple and effective second step into the world of gear box ratio tuning.