Underground Motorsports
Engine Parts
$369.00
150/160cc YX/GPX Race Head V2 Upgrade Kit:
Race Head V2 - Roller rockers, 30mm intake valve, 24.5mm exhaust valve, 27mm intake port, 23mm exhaust port (valves installed).
- Race Camshaft for Race Head V2
- Lightweight high compression domed 60mm piston with rings, pin, & clips
- Head gasket kit - includes the cylinder head o-ring set and an exhaust gasket.
This kit is to upgrade the cylinder head on stock YX/GPX 150 or 160 engines to our new Race Head V2. The addition of this new head will dramatically increase the performance of your stock engine!! This kit includes our new Race Head V2 and while the new head may appear to be the same on the outside as our other KLX110 type race head, internally it has gone through numerous changes. The addition of roller rocker arms and a new camshaft are the biggest changes followed by bigger valves and ports. The exhaust valve is now stainless as well (21-4N material). This all adds up to a cylinder head that puts out a professional level of performance yet is still affordable for the privateer rider. Also, included is a piston with bigger reliefs to match the larger valves of the new race head. Additionally, our head gasket kit includes a head o-ring set and exhaust gasket so you don't have to re-use your old ones or make a trip to your local dealer to get new ones and spend more money. These are high quality parts and require no machining to the cases or other modifications - bolt on and go!
150/160cc YX/GPX Race Head V2 Upgrade Kit:
Race Head V2 - Roller rockers, 30mm intake valve, 24.5mm exhaust valve, 27mm intake port, 23mm exhaust port (valves installed).
- Race Camshaft for Race Head V2
- Lightweight high compression domed 60mm piston with rings, pin, & clips
- Head gasket kit - includes the cylinder head o-ring set and an exhaust gasket.
This kit is to upgrade the cylinder head on stock YX/GPX 150 or 160 engines to our new Race Head V2. The addition of this new head will dramatically increase the performance of your stock engine!! This kit includes our new Race Head V2 and while the new head may appear to be the same on the outside as our other KLX110 type race head, internally it has gone through numerous changes. The addition of roller rocker arms and a new camshaft are the biggest changes followed by bigger valves and ports. The exhaust valve is now stainless as well (21-4N material). This all adds up to a cylinder head that puts out a professional level of performance yet is still affordable for the privateer rider. Also, included is a piston with bigger reliefs to match the larger valves of the new race head. Additionally, our head gasket kit includes a head o-ring set and exhaust gasket so you don't have to re-use your old ones or make a trip to your local dealer to get new ones and spend more money. These are high quality parts and require no machining to the cases or other modifications - bolt on and go!
$89.00
TB 150 160 V2 Race Head Decompression Option
Race Head V2 Decompression Valve Option – V2 Heads are machined and equipped with a decompression valve that eliminates high compression starting resulting in increased service life and reliability. The decompression valve releases compression in the big bore race engines upon startup so there is no need to start at TDC anymore. It was designed to eliminate common problems associated with high compression starting such as cracked and broken inner cases, broken kicker shafts etc. It's also easily accessible with an extended billet knurled end knob. To operate, just push the knob in prior to starting and kick it over nice and easy and that's it! The V2 Head will come with this option fully installed.
TB 150 160 V2 Race Head Decompression Option
Race Head V2 Decompression Valve Option – V2 Heads are machined and equipped with a decompression valve that eliminates high compression starting resulting in increased service life and reliability. The decompression valve releases compression in the big bore race engines upon startup so there is no need to start at TDC anymore. It was designed to eliminate common problems associated with high compression starting such as cracked and broken inner cases, broken kicker shafts etc. It's also easily accessible with an extended billet knurled end knob. To operate, just push the knob in prior to starting and kick it over nice and easy and that's it! The V2 Head will come with this option fully installed.
$179.00
170cc to 184cc Big Bore Kit:
- All aluminum ceramic plated 64mm cylinder with skirt
- NEW 6/28/10 We increased the skirt height and size on the lightweight high compression 64mm piston with rings, pin, & clips to increase reliability and service life (picture is not updated yet showing piston change)
- Head gasket kit - includes the cylinder head o-ring set and an exhaust gasket.
This is our most affordable 64mm bore kit for the YX/GPX/Zongchen engines. Works great with your stock head or our new V2 Race Head. The kit includes an all aluminum ceramic plated 64mm cylinder (with skirt) which will increase your engine displacement and power. This cylinder is lighter than a steel sleeved aluminum cylinder, reduces friction (increasing power), improves sealing, and provides better heat transfer (runs and cools down quicker). Additionally, our head gasket kit includes a head o-ring set and exhaust gasket so you don't have to re-use your old ones or make a trip to your local dealer to get new ones and spend more money. The new bore kit consists of high quality parts and requires no machining to the cases - bolt on and go! This kit is only for the YX/GPX/Zongchen 150cc to 160cc engines with a a KLX110 type topend. The increase in displacement will depend on your stock engine size. With this kit:
- A stock 150cc engine will increase to 170cc
- A stock 155cc engine will increase to 177cc
- A stock 160cc engine will increase to 184cc
170cc to 184cc Big Bore Kit:
- All aluminum ceramic plated 64mm cylinder with skirt
- NEW 6/28/10 We increased the skirt height and size on the lightweight high compression 64mm piston with rings, pin, & clips to increase reliability and service life (picture is not updated yet showing piston change)
- Head gasket kit - includes the cylinder head o-ring set and an exhaust gasket.
This is our most affordable 64mm bore kit for the YX/GPX/Zongchen engines. Works great with your stock head or our new V2 Race Head. The kit includes an all aluminum ceramic plated 64mm cylinder (with skirt) which will increase your engine displacement and power. This cylinder is lighter than a steel sleeved aluminum cylinder, reduces friction (increasing power), improves sealing, and provides better heat transfer (runs and cools down quicker). Additionally, our head gasket kit includes a head o-ring set and exhaust gasket so you don't have to re-use your old ones or make a trip to your local dealer to get new ones and spend more money. The new bore kit consists of high quality parts and requires no machining to the cases - bolt on and go! This kit is only for the YX/GPX/Zongchen 150cc to 160cc engines with a a KLX110 type topend. The increase in displacement will depend on your stock engine size. With this kit:
- A stock 150cc engine will increase to 170cc
- A stock 155cc engine will increase to 177cc
- A stock 160cc engine will increase to 184cc
$329.00
170cc to 184cc Big Bore Kit and 28mm Carburetor Performance Kit:
Same as bore kit but also includes Tb 28mm carb,with new rear facing intake(not klx style) jet kit,filter and throttle cable.
170cc to 184cc Big Bore Kit and 28mm Carburetor Performance Kit:
Same as bore kit but also includes Tb 28mm carb,with new rear facing intake(not klx style) jet kit,filter and throttle cable.
Quantity
Quantity
Quantity
Quantity