S3 SLAVENS MULE HIGH-COMPRESSION HEAD
The goal of the S3 head is to add performance, mainly bottom to mid-power. This is an area where the off-roader lives, making traction by having the ability to short-shift and lug his two-stroke when the going gets nasty. The Slavens Mule S3 head is CNC-machined, increases coolant capacity and has changeable inserts for either low elevation (0–6000 feet) or high elevation (6,000–12,000 feet). We’ve been testing an S3 high-compression head on our 2021 KTM 300XC with excellent results. The install was not complicated, and the power increase proved to be quite good.
Initially, we tested the S3 head with the stock ECU. At our 3,500 feet of elevation, it proved to be far too lean to do any major hill-climbing or put big loads on the motor. Slavens suggests an ECU update via the GET or Coober unit, and since we were testing the Coober ECU, things lined up quite nicely. Our TPI has been very strong to begin with, but the S3 head really woke the bike up. With the Coober ECU delivering the needed extra fuel for the now higher compression, we noticed a nice increase in bottom-end and midrange grunt. This was welcomed on our hard enduro loop, where lugging and loading the motor are key. The added bottom end propelled us up the steepest of climbs with zero run-up. The added top-end power was welcomed on nasty and sandy hill-climbs. The stock TPI machine tends to go flat, and with the S3 head, it really allows the bike to rev up quicker and stay in the meat of the power when you need it. It’s a very welcome addition to our bike for what we like to ride.