don't bother its a piece of complete crap
just stick with a pull starter I went roto on my G3 that I had in my MT2, as I had it in my savage. Well the roto start drains batteries FAST, mine would get stuck on, and I broke a con-rod when an engine flooded due to it (on my savage)
I wasted $100(+25 for the con-rod) going rotostart on back plates, battery, charger, and the unit itself just to go back to pull starts.
Another issue is after a few tries the battery(I used a 1800mah NiMh trust me you need at least 5000mah) won't have enough power to spin the roto start fast enough to start the engine. I've had to end my bashing sessions early a few times due to this...
On the HPI savage board most people tell new savage owners to ebay the starter, and buy a pull start
If you REALLY REALLY want it though if I were you I'd e-mail HPI and ask for the # as tower doesn't make it very clear which is for which engine...
Last thing make a note to make sure you have clearance behind the motor to shove the wand. My MT2 it was VERY hard to get it in position to start the engine due to the shock tower.