Topic: 1972 CB500 Questions About Breather Hose and Stock Airbox

[kyleighterry]

Hi everyone, I have a couple questions about a 1972 CB500 I recently acquired and am trying to get running. First off is the breather valve.. how do I run that hose? I’m been reading around and don’t have a sure answer. Some say to hook it up to the stock airbox, while others say to run it behind the engine to the ground. Also the stock 500 air filter doesn’t seat right.. seems like there’s a part I’m missing where it sits on cause it sits below the main filter hole to where the carbs are. Seems like the 550 air filter fits better but has a hole under it in the filter casting. Is there any reason running the 550 filter would be a bad idea? Any help would be appreciated. Thanks

[Deltarider]

The original as shown in the CB500 Parts Lists is the best.The hose is supposed to exit behind the engine. Some have it on the left, others on te right side. The tube is not to be attached to the airfilterbox. That is what Honda was forced ro do on the CB550s. It has often led to wettened/fouled paper airfilterelements.
The CB500 element is bigger and better than the 550 element. I can easily do > 20.000km with one. Renewing one can be done within 20 seconds.
All CB500/550 Parts Lists are here: https://www.honda4fun.com/materiale/documentazione-tecnica

[newday777]

Welcome to the forum kyleighterry
There were 3 or 4 changes in the air boxes and filters between the 1971 CB500 through the 1978 CB550 with lots of differences in parts. Stick with the CB500 air box and filter. It sounds like you have a mixmatch of parts?? Do you have the part numbers of each part you have?
The early CB550(74 &75) added an oil breather screen mesh with a bung that sticks up in the bottom of the filter that the 500 didn't have, thus the extra hole on the bottom you mentioned.
The CMS parts fiche shows a breather tube #13 going up to the air intake manifold but I'm not 100% sure where as I don't have a 500 to check with.

[newday777]

Here is the 74/75 CB550 fiche where you can see changes and the oil mesh bung #27 that sticks up into the filter bottom.

[dave500]

if its a 500 just have the tube run over the back of the motor,these were a draught tube,where tiny drops of oil just drop on the road,dont sweat it.

[bryanj]

There is nothing in any 500 filter box to keep the filter up only a spring to hold it forwards, is it possible you have a 550 filter box?

[CycleRanger]

Hello! Welcome!

You can download a copy of the shop manual and parts list from here:
https://www.honda4fun.com/materiale/documentazione-tecnica