Air suction valve, vacuum switch

[triton28]

The Canadian issue of a Voyager XII does not have any of the clean air gear and I was thinking of retrofitting mine to help scavenge the internal air pressure buildup. However after looking at the top end, section 4, pps7, of the service manual it appears to me as though the airflow is NOT from the cylinder head/engine internals through the vacuum switch then to the air filter box, but rather the air flows from the airbox through the vacuum switch to the cylinder head. I say this because the diagram shows the air flow during open throttle plate, ie low vacuum at the switch, entering the vacuum switch from the air filter box hose and exiting the switch through the cylinder head hoses. Add to this the orientation of the reed valves in their position on the cylinder head cover is for air entering the cylinder head cover, not exiting.
So my question is; have I got it wrong in my thinking that the air flow exits the cylinder head cover and flows into the air box similar to a PCV valve on a car, in order for the internal engine blowby gases to get reburnt in the combustion chamber?
Or, is this clean air gear designed to help force the blowby gases out the small tube from the lower airbox attached to the breather body?
And further, if the airflow is contrary to what I had thought, would there be any tangible benefit in scavenging pressure buildup within the engine castings by retrofitting this gear, or does the breather and tube to the lower airbox get all the pressure buildup within the engine on it's own without the clean air gear installed?
I'm confused about how this clean air gear works so any insight is appreciated.
Thanks,
Dave

[sheiserman]

I was looking at this from the opposite angle recently. While ordering parts for mine, I noticed the Canadian models were simply blocked off. You don't have the reed valves. I'm not sure what other differences there are between the two models. I'd say if some XIIs don't have this system, they obviously aren't vital to engine operation or performance. Keep in mind I'm a rank amateur.

I've tried doing internet searches on these reeds, and didn't come up with much. They seem to be oriented more for two-strokes. It surprised me how little information is openly available aout their purpose on an inline 4 motorcycle engine.

You asked for insight and I really can't help you with that. The videos I've seen on reed valves were limited to two strokes, and they seemed to act like a check valve for air/fuel mixtures. I don't know if, how, or why that would apply to an 4 stroke, or if it does. For what it is worth I thought these valves had as much to do with noise suppression as anything else. I can't remember if it was from a video or from reading, but an explanation of their location to the exhaust had something to do with their performance/effective operation.

In the end, I'm putting mine back the way I found 'em.

[sheiserman]

http://www.titantalk.com/forums/off-top ... alves.html" onclick="window.open(this.href);return false;

Noise suppression is not it...

And to be honest, I don't even know if this applies to a XII (seems like it should). It is the most detailed explanation for these reeds I've come across.

Are the Canadian models known to have problems without this reed feature?

[triton28]

Hello Sheiserman;
The Canadian models I have seen don't seem to have a problem without the "Clean Air" gear reed valves, vacuum switch and hoses, other than it seems as though there is more weepage at the gasket/o-ring/oil seal flanges than I would have thought normal. I'm sure the engineers at MawKaw would have known if this blanked off connection from the cylinder head covers would create a problem, but I was thinking that perhaps I could improve upon the breathing of the Canadian model engine I have. It may be an exercise in redundancy on my part as the tube from the breather body to the lower airbox may be sufficient, but I thought I'd like to hear what others think.
Thanks,
Dave

[sheiserman]

Given the lack of information on these things, they aren't a source of trouble or benefit to the operation of the engine. The whole system comes across as an add on in response to nanny-state legislation. It's just there.