SOHC.co.uk Forums > CB500/550
Any idea what this is?
Bryanj:
Probably cos the US insisted on the recirc for emmisions but Europe complained about oily air filters
McCabe-Thiele (Ted):
The "Muskie Bill" circa 1970's that resulted in U.S. legislation to reduce emissions and performance in the bargain on most new vehicles.
Hence the recirculation vent pipe ?
deltarider:
That blow-by gas system was forced on Honda and other bike manufacturers by US legislators. Some claim it was to reduce fumes into the open from the crankcase. I doubt that. I think it was more a consequence of legislation that already existed for trucks and cars, which in the past have fouled the turmac as these gasses always transport to some degree droplets of oil. Problem is that Honda had to improvise an extra on an already existing model and that shows. The design was poor (the CB400 and CB650 were better). In Holland there was no such legislation and some dealers would simply disconnect the breather tube from the airfilter case, if they had seen the paper filter elements got wettened/fouled. It's your choice, but know that the recirculation system does nothing good for the running of your engine. Personally I don't like the risk of other hydrocarbons than gas fed to the inlet valves.
beardylondon:
Sorry, I’m a bit unclear, are you saying to leave my bike as is, and not bother with this?
--- Quote from: deltarider on November 25, 2021, 04:53:22 PM ---That blow-by gas system was forced on Honda and other bike manufacturers by US legislators. Some claim it was to reduce fumes into the open from the crankcase. I doubt that. I think it was more a consequence of legislation that already existed for trucks and cars, which in the past have fouled the turmac as these gasses always transport to some degree droplets of oil. Problem is that Honda had to improvise an extra on an already existing model and that shows. The design was poor (the CB400 and CB650 were better). In Holland there was no such legislation and some dealers would simply disconnect the breather tube from the airfilter case, if they had seen the paper filter elements got wettened/fouled. It's your choice, but know that the recirculation system does nothing good for the running of your engine. Personally I don't like the risk of other hydrocarbons than gas fed to the inlet valves.
--- End quote ---
deltarider:
It's up to you. You can have it original, but then I'd check the air filter element regularly, or have it like the CB500 that didn't have that recirc system.
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