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BBR 88cc Flat Top Piston Bore Kit


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BBR 88cc Flat Top Piston Bore Kit
QTY    $
Any additional options and/or replacement parts will be available at the bottom of this page

BBR 88cc Flat Top Piston Bore Kit

Convert your CRF/XR50 to an 88cc screamer with this complete kit. Everything is included to upgrade the performance of you mini-bike. This kit uses your stock CRF/XR50 cylinder head.

Also fits 1988-1999 Z50R with short piston.

  • Aluminum BBR cylinder
  • Special 52mm piston specially designed to work with your stock cylinder head's combustion chamber
  • BBR special grind camshaft take full advantage of the large piston for great performance
  • Special BBR tapered aluminum intake manifold adapts the large carb to the stock intake port size
  • 18mm carb includes extra main and pilot jets for easy tuning
  • Also includes CR style throttle, cable, air filter and top end gasket kit

Installation Note 1: Throttle unit included with kit will only work with 7/8" handlebars and will not mount to stock XR/CRF50 handlebars. Stock handlebars are 3/4".

Installation Note 2: This kit will not work with the Honda XR/CRF70 or other big port cylinder heads. It is designed for the tiny combustion chamber of the OEM Honda XR/CRF50 cylinder head. The flat top piston dome will result in an extremely low compression ratio when combine with the XR/CRF70 type cylinder head. The result is a motor that makes less horsepower than stock. Click this link for the BBR bore kit for the CRF/XR70.

BBR General Jetting Guidelines Chart

Tech Info
411-HXR-5400 Instructions

Part NumberImageDescriptionPrice 
411-HXR-5400411-HXR-5400Bore Kit - 88cc FTP W/Cam & Carb Kit, XR/CRF50,

Replacement Parts

Part NumberImageDescriptionPrice 
411-HXR-5210411-HXR-5210Gasket Kit - 88cc S/P-FTP Kit / XR/CRF50/
411-HXR-5212411-HXR-5212Ring Set - 88cc/106cc S/P-FTP Kit / XR/CRF50/
411-HXR-5250411-HXR-5250Cylinder - BBR Aluminum, 52mm / XR/
411-HXR-5411411-HXR-5411Piston Kit - 88cc FTP Bore Kit / XR/
411-HXR-5416411-HXR-5416Piston Pin - 88cc FTP Bore Kit / XR/
411-HXR-5417411-HXR-5417Piston Pin Clips (2) - 88cc FTP Bore Kit / XR/
421-BBR-2001421-BBR-2001Carburetor Only - 18mm (80m/35p)
422-HXR-5003422-HXR-5003Intake Manifold - XR/CRF50/PC18/Stock
512-BBR-1001512-BBR-1001Throttle Cable - BBR 18mm/26mm Carb Kit / XR/CRF50 / KLX/DRZ110 / Bar Kit - CRF110F /
512-BBR-2001512-BBR-2001Throttle Assembly - BBR Carb Kits / Brake

Optional Parts

Part NumberImageDescriptionPrice 
410-HXR-5005410-HXR-5005Clutch Springs - HD / XR/CRF50,
430-HXR-5002430-HXR-5002Air Filter - UNI, 1 1/4"(32mm) X 4", Straight / 18mm Carb / XR/CRF70 Stock
451-HXR-5001451-HXR-5001Rev Box - Honda / XR/CRF50/70/80/
Prop 65 Warning