KTM 125SX TSP RADIUS™ Head and Piston Kit 2016-2017


KTM 125SX TSP RADIUS™ Head and Piston Kit 2016-2017


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This TSP RADIUS™ kit has been custom designed in-house at TSP. We are very proud of this kit and the huge performance gains it offers compared to other products on the market!

Our head insert and matching piston have been CNC machined in-house with a custom profile that not only improves combustion efficiency but also enables much better cooling of the piston and flow through the ports… and we can prove it on the dyno!

Our own dyno testing shows a huge 5% gain throughout the rev range when compared to a stock bike (with all other tuning specs kept the same)… that means an extra 1.5hp at 8,000rpm and a massive 2hp more than stock at 11,600rpm… plus it offers better overrev, making at least 5% more power all the way to 13,000+ rpm over a stock bike.

No other product on the market can offer better bottom, better mid, better peak AND better overrev!!


The kit contains:

1 x custom TSP head insert (Med-Comp) which fits perfectly into the stock head outer shell

1 x custom TSP machined piston in the size of your choice (A or B only, Wossner or Pro X supplied)

1 x genuine KTM base gasket in the required thickness to set the correct deck height

1 set of genuine KTM head O rings (inner and outer)

1 x upper O ring to seal around the top of the insert


PLUS upgrade to an extra insert for only $150 more (your choice of Lo-Comp or Hi-Comp), or add both extra inserts for only $250 more!!


Images for illustration purposes only. You will receive all the parts listed above.


1. Whats involved in fitting this kit?
Simply remove the head and cylinder, replace the stock piston with the custom TSP machined piston, fit the new base gasket provided, refit the cylinder, refit the head using the new TSP RADIUS insert and new head O rings.

2. Is any other tuning required?
Our dyno testing has shown that the kit has minimal impact on the jetting requirements of the engine. All dyno tests were done using stock jetting specs and our tests show that the engine actually ran slightly richer at peak hp when our RADIUS kit was fitted. Of course you will still need to make sure that the bike is jetting according to your riding style and local conditions.

3. Can I return the engine to stock later?
Yes, you can. Just remove the TSP insert, piston and base gasket and refit the stock base gasket, piston and head insert.

4. Will this kit work with other mods?
Yes it will. Ask us about other mods we offer to further increase power on this engine.

5. Can i run a different piston with the TSP head insert, or a different head insert with the TSP piston?
No. Both the TSP head insert and TSP machined piston must be run together at all times.



Additional information

Piston Size


Extra head inserts

Add 1 extra Hi-Comp insert (+$150), Add 1 extra Lo-Comp insert (+$150), Add both Lo-comp and Hi-Comp inserts (+$250), No thanks, Im happy with the Med-Comp insert.


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