BCS Part #635-01
The Bunn Crankcase Breather Kit

The Bunn Breather Kit (BBK)… Cuts Oil Leaks AND Reduces Engine Wear, as it Flushes Toxic Blowby from your Crankcase & Rockerbox. It is warranted in use for two years with unlimited mileage.

The new Kit cuts oil leaks by restoring original crankcase air pressure, back to the levels classic designers planned. Over the decades, the OEM breathers malfunction and air pressure increases. Oil leaks are often the first sign. The Kit suits all the usual four-stroke makes, whether singles, twins or multi-cylinder engines, i.e. AJS, Ariel, BSA, Harley Davidson, Indian, Matchless, Norton, Sunbeam, Triumph, Velocette, Vincent. The BBK Kit also cuts engine wear by flushing filtered, fresh air through your crankcase. This controlled airflow forces out corrosive blowby gases that otherwise cause this damage to your engine, each time we start up:- * Contaminates and dilutes oil * Washes oil film off engine internals * Rusts ferrous components and bearings * Sludge forms * Pressurized crankcase causes oil leaks * Rubber deteriorates * Crankcase becomes a fire hazard.

The BBK Kit includes- valves, air filter, tubing, cable ties/clip, spare seal and comprehensive instructions. It's a simple, easy-to-install solution for classic engine oil leaks, crankcase pressure problems and blowby wear and corrosion. It can be fitted to nearly any four-stroke engine, to improve engine operation. It involves no permanent or unsightly changes to your engine. Flowing fresh, filtered air through the hot, closed-off rockerboxes and crankcase helps oil return and the engine to run cooler. It also helps prevent any dirt being sucked into the engine via existing oil leaks. Engine power may be enhanced on some bikes, as crankcase air pressure, downforce work-loads and drag reduce. Research shows oil leaks are signs of more serious problems. Noted Classic engineer and Norton racer Peter Williams says, in his June 2005 Classic Bike review of engine breathing..."...leaked blow-by gas is nasty, obnoxious, and corrosive stuff and it is best to have as little as possible in the crankcase..." Blowby occurs every time we ride. It forms a corrosive, flammable mixture, that eats away at our engines, if left inside. Blowby is ~70% fuel, water, sulphur dioxide, nitrogen oxides, soot and ash. It's like a concentrated acid rain. The BBK Kit is an effective conservation aid, designed to keep classic motorcycles on the road into their second century.

Disclaimer: As user installation and operation vary widely, this kit is not guaranteed to work on every make and model of classic motorcycle; for instance, some J.A.P. engines.

Universal Kit

“””Carlel Pty. Ltd Data Sheet no.18                                                       31/10/2007 US Edition

Copyright 2007                                                                                                       Intn. Patents Pending

                          The Bunn Breather - User Guide for the Universal Kit

1.0  Introduction: - The Bunn Breather takes over management of the crankcase, bringing air pressure and air flow under rider control for the first time. It meters air into the crankcase, while pumping out corrosive blow-by gas. Bunn technology is well researched and operating in a series of >500 classic and modern engines. It’s easy to fit. It controls crankcase pressure and flows, cuts power loss and oil leaks and pumps out toxic blow-by. The Bunn preserves oil viscosity and lubricity. The valve seals are warranted for five years over unlimited mileage. Fitting advice & pics are available for many marques.

2.0 Bunn Breather Kit Contents:-

       2.1 One Bunn Inlet valve, [the small valve…note flow arrow shown on valve]

       2.2 One Bunn Exhaust valve, [the large valve…note flow arrow shown on valve]

       2.3 The User Guide, a step-by-step guide to installing the Kit,

       2.4 Tubing, 500mm each of 8mm and 10mm CVT, to connect breathers to engine,

       2.5 One high-flow 2-5micron air filter and stainless clip for the Bunn Inlet breather,

       2.6 Carlel card. Please retain for technical advice and warranty.

       2.7 Cable ties in a range of sizes to secure air filter and tubing.

       2.8 Spring tubing clamps to fit 8mm and 10mm CVT.

       2.9 Discount Voucher for my new book “Classic Motorcycling: A Guide for the 21st Century”                                                                                                                                        

3.0 Installing the Bunn Breather- The Bunn Breather uses two access points into the crankcase or connected compartments i.e. rocker/cam boxes, timing cases or chaincases. This allows the patented crankcase pumping action to operate. The Bunn Breather routes air flow “top>down”, ‘bottom>up”, “bottom>bottom”, or “top>top”, depending on bike configuration, oil fling patterns and your choice. A typical “Top>Down” breather installation is detailed below. (Refer Figure 1) 

   3.1 Bunn Inlet Breather - Use any existing rocker/camshaft box breather. If you have no second

             breather, here's a step-by step guide for one, using the rocker cover:-

       (a) Unscrew a  rockerbox hatch-cover, either inlet or exhaust.

       (b) At an air tool/camping/auto shop; buy a 1/8”, 3/16” or 1/4" brass union, [threaded & barbed]

       (c) Tap it into your rocker hatch, with the inside flush-fitting.

       (d) Reinstall the hatch-cover. ** NB: Check the union does not foul the valve gear.

       (e) Locate a sheltered spot for the air filter, e.g. under seat, tank,  toolbox or battery, or a sidecover.

       (f) Secure filter to frame with cable ties, foam, rubber or a P-bracket.

       (g) Cut and warm 20mm of the 8mm size tube and fit over Inlet valve, on the air filter side.

       (h) Insert valve into air filter and tighten with clip (supplied). Ensure the Bunn Inlet valve, has its

            arrow pointing TO the engine.        

       (i) Connect the air filter/valve assembly to the rockerbox union using the 8mm tubing (supplied).

NB: Before installing valves, do a “Blow-Test”. Blow in Inlet line and check air flows out Exhaust line….”””                                                                                                                             

Royal Enfield Kit

“””Carlel Pty. Ltd Data Sheet no.17                                                      31/10/2007 US Edition

  Copyright 2007                                                                                             Intn. Patents Pending

Bunn Breather Kit- User Guide for Royal Enfield Bullet, Classic, De Luxe & Electra            

1.0   Introduction: - The Bunn Breather manages the crankcase, bringing air pressure and air flow under rider control. It meters air into the crankcase, while pumping out corrosive blow-by gas. Bunn technology is well researched and operating in >500 engines. It’s easy to fit. It controls crankcase pressure & flows, cuts power loss & oil leaks & pumps out blow-by. The Bunn Breather preserves oil viscosity and lubricity. Seals warranted for five years & unlimited mileage.

2.0  2.0 Bunn Breather Kit Contents:-

       2.1 One Bunn Inlet valve, [the smaller valve…note flow direction arrow shown on valve]

       2.2 One Bunn Exhaust valve [the larger valve…note flow direction arrow shown on valve]

       2.3 The Bunn-Royal Enfield User Guide, a step-by-step guide to installing the Kit,

       2.4 Tubing, 700mm of 8mm and 500mm of 10mm CVT [with twin baffles] to connect to engine,

       2.5 One high-flow 2-5 micron air filter and stainless clip for the Bunn Inlet breather,

       2.6 Carlel card. Please retain for technical advice and warranty.

       2.7 Cable ties in a range of sizes to secure air filter and tubing.

       2.8 One dust cap for the Electra aircleaner breather union.

       2.9 Discount Voucher for my new book “Classic Motorcycling: A Guide for the 21st Century” 3.0 Installing the Bunn Breather- (Refer Figure 1) For the Royal Enfield Classic, de Luxe and Electra models, the Bunn Breather replaces the OEM breather tubes, duckbills and canister. The Bunn Inlet breather connects to the existing timing chest union. The Bunn Exhaust breather connects to the existing oil tank union.  The existing breather tubes on earlier Bullets may vary. British Bullets connect via the OEM barrel breather and one other union.

NB: Before installing valves do a “Blow-Test”. Blow in Inlet and check air flows out Exhaust line.

3.1 Classic Installation-

  3.1.1 Bunn Inlet Breather            

(i) Open the right sidecover and install the Bunn air filter in the top left corner, with double-sided adhesive tape or Velcro; or cable ties or a P-bracket to the bolt. Adhesive foam stops chafing.

(ii) Remove the black OEM breather tube connecting the timing case union to the OEM canister. Retain the clips for re-use with the CVT. The canister can be removed or left. It is not required.

(iii)  The timing case union is converted to the Bunn Inlet. Curve the 8mm CVT (clear vinyl tube supplied), back across the oil tank, (see pics on the R.E. Australia website or emailed on request). Take it up the frame, into the right sidecover through air inlet. Curve it around to meet the air filter.

(iv) Warm & cut 20mm of 8mm tube and fit to Bunn Inlet valve, on the filter side. Insert valve in filter & tighten clip. Ensure Bunn Inlet valve arrow points to the engine.  Join 8mm tube to the valve.

(v) Run 8mm tube down frame to timing union. Trim it and push onto union. Secure with OEM metal clip. Ensure the tube rises smoothly to the Inlet valve, avoiding tight curves for best air flow.

Comments: - The Breather distills any sump-water and pumps it out over 50-100kms. Expect moisture in the Exhaust breather over start-up and the first 5-10kms on runs. The tube then clears.   

Technical Note: - At idle, oil may enter 10-20cm up the Inlet tube from the timing case. This is returned to the timing case above idle speed. This is normal for the Classic and is of no concern.