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We offer Big Bore kits for most late model two stroke dirtbikes. These kits are a great way to bump up power and torque and often dont cost much more than a normal top end rebuild, especially if your stock plated cylinder is worn or damaged.
These big bore kits have proper porting and proper head designs to suit local fuels and conditions and as a result they offer MUCH better performance than most of the usual aftermarket big bore cylinder kits.
Send us your complete top end (old base gasket, cylinder, old head gasket, old piston, head) and we will bore, port and replate your cylinder, machine your powervalve to suit the new bore size, design and machine the head to give correct squish clearance and compression ratio and we’ll also supply a piston kit and top end gasket set.
When you receive the big bore kit it will be ready to install onto your bottom end and ride! Some kits may require carb and powervalve tuning to get the most of the new setup. Some kits require case mods. Please allow 2-4 weeks for return of your parts.
Final tuning will be the responsibility of the installer unless dyno tuning is requested.
| Big bore kit | From |
| Below 134cc (up to 52mm bore) | $1399 |
| 134, 139 and 144cc (up to 58mm bore) | $1500 |
| 265cc (68.5mm bore) | $1600 |
| 295cc (72mm bore) | $1650 |
Check out the following list to see what big bore kits we offer for your model…
| Honda | |||
| Model | Year | Displacement | Special Notes |
| CR80/85 | 1986-07 | 92cc | |
| CR80 | 1986-07 | 100cc | |
| CR85 | 2005-07 | 92/100cc | Must install oversized radiator |
| CR125 | 1972-88 | 134cc | |
| CR125 | 1989-04 | 134cc | |
| CR125 | 1989-99 | 144cc | |
| CR125 | 2005-07 | 134cc | |
| CR125 | 2005-07 | 139 or 144cc | |
| CR250 | 1978-80 | 265cc | |
| CR250 | 1986-07 | 265cc | |
| Kawasaki | |||
| Model | Year | Displacement | Special Notes |
| KX60 | 1983-2003 | 66cc | |
| KX65 | 2000-14 | 72cc | |
| KX80/85 | 1988-2014 | 92cc | |
| KX80/85 | 1988-2014 | 100cc | |
| KX80/85/100 | 1988-2014 | 107cc | |
| KX125 | 1985-1993 | 134cc | |
| KX125 | 1994-2014 | 144cc | |
| KDX200 | 1986-88 | 212cc | |
| KDX200 | 1995-2006 | 225cc | |
| KX250 | 1987-2007 | 265cc | |
| KX250 | 1993-2007 | 295cc | |
| KX500 | 1985-2001 | 525cc | |
| Suzuki | |||
| Model | Year | Displacement | Special Notes |
| RM65 | 2003-05 | 72cc | |
| RM85 | 2002-14 | 92cc | Crankcase clearance mods needed |
| RM85 | 2002-14 | 100cc | Crankcase clearance mods needed |
| RM125 | 1976-88 | 134cc | |
| RM125 | 1989-2009 | 144cc | Crankcase clearance mods needed |
| RM250 | 1989-2008 | 265cc | |
| RM250 | 2003-08 | 295cc | |
| Yamaha | |||
| Model | Year | Displacement | Notes |
| PW50 | 1990-14 | 60cc | |
| YZ80/85 | 1993-2014 | 105cc | Crankcase clearance mods needed |
| YZ125 | 1976-89 | 134cc | |
| YZ125 | 1990-93 | 129cc | |
| YZ125 | 1994-2014 | 134cc | |
| YZ125 | 1994-2014 | 144cc | Crankcase clearance mods needed |
| YZ250 | 1979-89 | 265cc | |
| YZ250 | 1990-2014 | 265cc | |
| YZ250 | 1999-2014 | 295cc | |
| YZ/IT465 | 1980-81 | 478cc | |
| YZ490/WR500 | 1983-93 | 510cc | |
| Husqvarna | |||
| Model | Year | Displacement | Special Notes |
| CR/WR125 | 1998-2011 | 144cc | |
| CR250 | 1998-2009 | 265cc | |
| CR250 | 1998-2014 | 295cc | |
| Gas Gas | |||
| Model | Year | Displacement | Special Notes |
| 125 all models | 2000-2014 | 144cc | |
| 250 all models | 2000-14 | 265cc | |
| KTM | |||
| Model | Year | Displacement | Special Notes |
| 50SX LC | 2001-08 | 58cc | |
| 50SX | 2009-14 | 58cc | |
| 65SX/XC | 1999-08 | 72cc | |
| 65SX/XC | 2009-14 | 72cc | |
| 105SX | 2004-14 | 112cc | |
| 125SX/EXC | 2001 | 134cc | |
| 125SX/EXC | 2001 | 144cc | |
| 125SX/EXC | 2002-14 | 144cc | |
| 150SX | 2007-14 | 155cc | |
| 200EXC/MXC/XC-W | 1998-12 | 212cc | |
| 250SX/EXC | 1996-05 | 295cc | |
| 300EXC/MXC | 1991-14 | 310cc | |
| TM | |||
| Model | Year | Displacement | Special Notes |
| 125 | 1998-2007 | 144cc | |
| 250 | 1998-2013 | 265cc | |
