DHM High Compression Stock Bore Piston (Gen 2)

DH Motoring

Regular price $120.00

Shipping calculated at checkout.

Customer Reviews

Based on 31 reviews
Ben Douglass

Great product

Javier Paris Roman

Fast shipping

Excellent bang for the buck!

I previously installed an aftermarket intake, exhaust, a TB Cam, and finally this little high comp piston to round out my goal of getting more power without the stress of going big bore and (possibly) blowing up my motor (and also having the extra expense of needing to add cooling and fueling ECU like aRacer). Just in case, I had Cameron Jones Racing reflash my ECU to wring out the potential in my mods. My top speed WAS 62 mph stock, 72 with intake, exhaust, and cam, and now I'm getting about 74/75 (as of my last try a few days ago). I might be able to get more, but I'm still breaking the new piston in, so I didn't redline it. Maintaining 60 mph is easy now! The caveats... I don't think swapping out the stock piston by itself would really make a difference, but IN ADDITION to all of the other mods, the bike definitely makes more power, especially in the mid to high rpm. Just don't forget to set the RPM limit higher to take advantage of the added horsepower and power band. I'm using stock gearing, and I'm positive that going 14 tooth would make this thing wheelie! I think, if you're doing a cam swap, you owe it to yourself to get this piston as well. Just don't forget to reflash the ECU as mentioned earlier, otherwise, you wont see the gains.

Logistically... excellent packaging and fast delivery. They even included all the gaskets, rings, etc needed for the install. They didn't have the recommended spark plug in stock, so I just ordered one online. From ordering to install - I had everything done within about 10 days (would have done it within a week, but I had to adult a few days before I could get the install completed). A++ product and company!!

William Conklin
Not worth it..

I’m not happy at all! I have no power change in bike! I have entire stage 3 kit and i feel it was a waist of money. I have intake mod I have zoom loop exhaust and everything checks out perfect, timing marks valve adjustment. I had better throttle response and power with messed up stock parts inside motor.

Bret T
Awesome parts and company

Love the hc piston on my super 125 build. Brought all my mods together perfect. Plus supper fast shipping!!! Yall are amazing

DH Motoring Stock Bore Racing Piston (Gen 2)

The DHM Race-spec stock bore piston has produced more HP than any other stock bore kit and is the highest compression stock bore piston on the market. It has a high compression dome that is made exclusively for us and isn't available anywhere else. It's gone through extensive testing on the racetrack and has proven to provide the most power possible from the stock bore. 

  • ~13.2:1 compression 52.4mm stock bore piston
  • Larger ring and skirt oiling holes than other pistons on the market
  • Larger oil spring to increase oil volume between the oiling rings
  • Oil ports under the pin holes to keep the wrist pin lubricated
  • 360 Degree skirt design to increase overall strength
  • Racing piston ring kit with pins and circlips
  • Valve reliefs that clear valves up to 27.5/23.5 cylinder head valves
  • Includes a new base gasket and head gasket
  • Requires NGK CR9E (6263) spark plug 
  • Requires at least 91 octane fuel

Over the past 6 years we've raced with and tested over a dozen different stock bore pistons. Using our experience on the racetrack we've now designed and produced the most competitive and reliable stock bore piston on the market. We targeted increased lubrication while also pushing the compression limits for pump fuel and ended up with what we feel is the most refined 125cc piston available. By enlarging the oiling holes that feed the oil spring channel and skirt, the piston stays well lubricated at all RPM which allows for extended high RPM use. Valve reliefs have been sized to allow the largest valves possible with the stock bore and they have been cut deep enough to ensure compatibility with even the highest lift cams on the market. 

Install video:

**Installing this piston requires setting the ring gaps. If you are not comfortable with this, please have your local shop perform the install. Failure to set the proper piston ring end gap can result in premature failure or seizure of the engine. We recommend an end gap of .007-.009" on the top ring and .009-.011" on the bottom ring. The silver ring goes on top and the black ring below. Unknown Overland does a great job of explaining this in the video below.