There is a fine line to engine building

If the limits are pushed too far (as many engine builders do) there are reliability issues. Heavy Duty Racing's goal is to give you the very best in high-performance service, without any loss of reliability. At Heavy Duty Racing, we can design an engine package for your 2 or 4 stroke, weather you want more bottom and mid-range for woods riding, arena cross or SX or more mid and top end for an expert level motocross racer. Perhaps you just want a broader spread of power.

From two-strokes to four-strokes, race bikes to ATV’s, almost any machine can benefit from our engine modifications.

Engine Services

 

Dyno run

Here is a Dyno graph of an all stock 2006 Yamaha YZ 125 (blue line 31.25HP) before our YZ 144 big bore cylinder treatment. The Red graph (39.19HP) is after we overbored, ported and replated the cylinder. The cylinder head was also modified for the bigger bore and to correct the compression ratio and the squish velocity. Peak HP of the big bore cylinder is at 11,500 RPM.

 

2 stroke head

This picture shows the typical finish we put on our 2 stroke heads after machining them.

 

Ported head

In this picture you see a Kawasaki KX 65 cylinder that we have ported. You will notoce that we have machined in Boost ports around the back of the cylinder sleeve. This really helps the little KX make better all around power.

 

Resleaved cylinder

In this photo you see a cylinder of a 2009/2010 Honda CRF450R. It has been resleeved by HDR with a wet cylinder sleeve. A wet cylinder sleeve actually makes up the inner wall of the water jacket so you have realy good heat transfer and you do not have to worry about any overheating problems. The actual displacement has been brought up to 490cc.

 

refinished piston

This is a 100mm JE piston that yields a compression ratio of 12.5:1 This cylinder kit has proven to be very reliable on the motocross track.