Honda CX 500 Forum banner
1 - 20 of 26 Posts

·
Registered
Joined
·
38 Posts
Discussion Starter · #1 · (Edited)
Hello,
I have a question about the crankcase breathers, Most of the post are very old or don't really answer may question.
My 80' CX500D originally had the breather ports coming out of the back of the heads and join up and go to the air box, I am going with the POD filters and my plan was to buy or make a catch can to deal with the oil coming out of the breather ports. This is when I came across that the older generation 500's had a "bottle" coming out of the inspection port.
Cylinder Auto part Metal Nickel Titanium
(example picture of the Bottle)

So to my question,
Is it beneficial to use the inspection breather?
Would it be better to use both Head breather and inspection breather, or just one, and if so why?

I really appreciate all of knowledge that everyone has here.


Thank you
 

·
Registered
Joined
·
1,403 Posts
Those breather bottles were first fitted to 1981 models (at least, in markets other than the US), not earlier models. A kit was available to retro-fit to earlier models, which is why many earlier bikes have them fitted. They were still piped to the airbox.
 

·
Registered
Joined
·
2,560 Posts
I would suppose the reason for the pictured “bottle” (my GL650i has one) is to allow a larger diameter vent for the first few inches so less velocity inside allows more of the oil mist to drop out and run back into the engine for slightly less oil consumption and perhaps improved environmental numbers.
 

·
Registered
Joined
·
38 Posts
Discussion Starter · #4 ·
ier bikes have them fitted. Th
I would suppose the reason for the pictured “bottle” (my GL650i has one) is to allow a larger diameter vent for the first few inches so less velocity inside allows more of the oil mist to drop out and run back into the engine for slightly less oil consumption and perhaps improved environmental numbers.
I understand the design on the bottle, but my bike currently has the ports coming out of the top of the heads, and honda changed it for a reason. I just wanted to know if it is a good idea to switch to, and if so should I also use the ports in the top of the head
 

·
Registered
Joined
·
2,560 Posts
IMO the change would be a very small improvement, and atheistically a step backwards. Just my opinion. And I don’t know if Honda made any other internal changes related to the relocated breather. It does make opening that port a little more cumbersome. I wouldn’t bother changing either for the other. Seems inconsequential to me. 🤷🏻‍♂️
 
  • Like
Reactions: LaGrasta

·
Super Moderator
Joined
·
23,405 Posts
The head breathers pump more oil due to their high location in relation to the low location of the catch tank/separator on high milage motors.

On a lower milage motor this shouldn't matter but will with a motor that has excessive blowby.

With the bottle breather this will return more oil to the motor if a longer hose is fitted and looped higher than the OEM hose. Condensed water tends to leave as steam so this is not effected as much as the oil.
 

·
Registered
Joined
·
1,403 Posts
I understand the design on the bottle, but my bike currently has the ports coming out of the top of the heads, and honda changed it for a reason. I just wanted to know if it is a good idea to switch to, and if so should I also use the ports in the top of the head
The bottle breather kit replaced the head vents, for which blanking covers were provided in the kit.
 

·
Registered
Joined
·
38 Posts
Discussion Starter · #8 ·
The head breathers pump more oil due to their high location in relation to the low location of the catch tank/separator on high milage motors.

On a lower milage motor this shouldn't matter but will with a motor that has excessive blowby.

With the bottle breather this will return more oil to the motor if a longer hose is fitted and looped higher than the OEM hose. Condensed water tends to leave as steam so this is not effected as much as the oil.
My cx I think has around 17k, but I do remember the air box had a ton of oil in it. I get richnct point of the atheistically look cleaner with out the bottle, but I also don't want to be constantly cleaning up the oil or draining the catch can.
 

·
Super Moderator
Joined
·
23,405 Posts
At 17K has the bike been laid up for some time?

Long periods of inactivity will allow the rings to gum into their grooves giving low compression and excessive blowby.

This generally sorts itself out with a few hundred miles use.

Alternatively the airbox has not been drained in a long time.
 

·
Registered
Joined
·
38 Posts
Discussion Starter · #10 ·
At 17K has the bike been laid up for some time?

Long periods of inactivity will allow the rings to gum into their grooves giving low compression and excessive blowby.

This generally sorts itself out with a few hundred miles use.

Alternatively the airbox has not been drained in a long time.
Yeah, that's make sense. Before I got it, I believe is said in a bush for maybe a bit less then 10 years. But after I cleaned the varnish out of the carbs she fired up with out to much complaining. I only put make 50 miles on it before the make shift gas tank I had ran out.

So you saying that after I get her going again that the first while or riding I will get a bunch of oil in my catch can But it should lessen over time?
In the past I fixed up a few only vw bugs, and to help clean the engine in those I would mix some sea foam and a quart of oil and manually turn the motor over a few times per day for a week or so, I have never tired this on a bike. Do you think that would help or hurt anything?
 

·
Super Moderator
Joined
·
23,405 Posts
Yes, the oil SHOULD lessen over time once the bike has been in use for a while. Do you have any compression readings?

I'm really not familiar with seafoam but from what I've read it should maybe help.

In this circumstance I tend to use cheap supermarket oil until the first oil change as it tends to be high detergent.
 

·
Registered
Joined
·
38 Posts
Discussion Starter · #12 ·
Yes, the oil SHOULD lessen over time once the bike has been in use for a while. Do you have any compression readings?

I'm really not familiar with seafoam but from what I've read it should maybe help.

In this circumstance I tend to use cheap supermarket oil until the first oil change as it tends to be high detergent.
I don't have an official reading, I don't have the gauge to test it. But did try to plug the spark plug hole and try to manually turn the engine over and it blew the pug out, it did make a really cool sound when it popped.
 

·
Super Moderator
Joined
·
23,405 Posts
Compression figure would be helpful but we can live without it.

The bottom line is that your motor starts and runs.

A basline compression would be handy for two reasons though - What is the compression now and does it improve with use?

My first CX had low compression when purchased. Checked while troubleshooting some years later I was surprised to find 170 PSI per side.
 

·
Super Moderator
'84 CX650E that is evolving into a GL500
Joined
·
17,743 Posts
The head breathers pump more oil due to their high location in relation to the low location of the catch tank/separator
<<<<

With the bottle breather this will return more oil to the motor if a longer hose is fitted and looped higher than the OEM hose. Condensed water tends to leave as steam so this is not effected as much as the oil.
Interesting. When I had the 650 engines in Eccles they always used a lot more oil than I would have liked. I wonder if adding a bottle breather would have helped with that?
But then, TI engines breathe through their timing covers which are about the same height as the bottle would be...
 

·
Registered
1982 CX500C
Joined
·
82 Posts
This may be a situation where you just have to install the bottle type breather and see if it makes a difference, for better or worse.

Besides emission control, the breather system is designed to maintain crankcase pressure at or near zero - too much positive pressure will cause gaskets and seals to leak - too much negative pressure (vacuum) and the sealing effect of the rings can be overcome by combustion, causing excess blow by.

This is accomplished with some kind of orifice that varies by application.

Changing the type of breather system and/or re-routing the breather hose may or may not be a good thing - I don’t know the calculations used to determine the correct size of a breather orifice for a given crankcase volume.
 

·
Registered
CX500 Z 1978 , Rickman Polaris fairing, currently GL500 front, Ignitech etc. subject to change
Joined
·
306 Posts
Keep it simple : Honda didn't redesign this for fun. I changed to the bottle type simply for that reason but it doesn't make a blind bit of difference AFAIK - for my bike. Shut the "old" outlets by replacing the T-piece with a straigth tube, makes the engine look complicated ;)
 

·
Registered
Joined
·
24,495 Posts
honda brought out the bottle breather kit and told us to install it on gl650s and gl500 to stop high oil consumption when running at our higher highway speeds
the breather kit relieved crankcase pressure and lower oil getting by the oil control rings on the gl650 as a main point
they used the bottle rather in conjunction with the pulse generator vent to get enough vent area on ti equipped bikes I have never seen one installed in north America on a cdi bike from the factory

the other thing I can say from my time with these is her e in north America for sure in damp and cold weather I would really prefer the cylinder head vents over any other
the reason for it is simple RUST when I pull a part a engine with the head vents they are clean and dry as the vents in the head raw the moisture that accumulates on the inside of the rocker cover from condensation and them being cooler that the engine while running
on the other hand in cold weather places I have seen a lot of rust on the rocker assemblies due to condensation and it not being drawn out the bottom

further to that honda has always had the bottle rather coupled to the pulse generator cover to allow for 2 exits just like the 2 on the heads

1 vent only from a bottle breather has never been done from that factory as far as I know on the cx500 and I dint think it will provide enough vent area considering the windage pressure a cx can generate

I would not plug the head vents in fact on performance gl engines that I boost or raise compression on I drill the cylinder head pads and tap them for 1/8 npt then put a 1/8 npt pipe nipple in to put vent hoses on

just my thoughts
 

·
Registered
1978 CX500 "The Grub", 1983 GL650I "Nimbus"
Joined
·
11,456 Posts

·
Registered
Joined
·
1,403 Posts
honda brought out the bottle breather kit and told us to install it on gl650s and gl500 to stop high oil consumption when running at our higher highway speeds
the breather kit relieved crankcase pressure and lower oil getting by the oil control rings on the gl650 as a main point
they used the bottle rather in conjunction with the pulse generator vent to get enough vent area on ti equipped bikes I have never seen one installed in north America on a cdi bike from the factory

the other thing I can say from my time with these is her e in north America for sure in damp and cold weather I would really prefer the cylinder head vents over any other
the reason for it is simple RUST when I pull a part a engine with the head vents they are clean and dry as the vents in the head raw the moisture that accumulates on the inside of the rocker cover from condensation and them being cooler that the engine while running
on the other hand in cold weather places I have seen a lot of rust on the rocker assemblies due to condensation and it not being drawn out the bottom

further to that honda has always had the bottle rather coupled to the pulse generator cover to allow for 2 exits just like the 2 on the heads

1 vent only from a bottle breather has never been done from that factory as far as I know on the cx500 and I dint think it will provide enough vent area considering the windage pressure a cx can generate

I would not plug the head vents in fact on performance gl engines that I boost or raise compression on I drill the cylinder head pads and tap them for 1/8 npt then put a 1/8 npt pipe nipple in to put vent hoses on

just my thoughts
I don't know about the North American models, but in most markets the1981 'B' models (still CDI), on both the Standard and Custom, had the bottle crankcase breather only from the factory. The head breather points were never even drilled out.
 

·
Super Moderator
Joined
·
23,405 Posts
I don't know about the North American models, but in most markets the1981 'B' models (still CDI), on both the Standard and Custom, had the bottle crankcase breather only from the factory. The head breather points were never even drilled out.

80 and 81 here. Just the bottle, heads undrilled.
 
1 - 20 of 26 Posts
Top