internal pressure?

Stephen Hampson shampson at
Sun Mar 18 09:25:58 PDT 2007

I have left it on the GPz as its stock all round. But on my VN1500 I have
aftermarket exhausts and air filter so it made sense to remove it. I don't
know if it's the same on the GPz but somehow by removing the reed valve or
blocking them of, it helps with the cooling of the engine on the Vn, the
cooling fan does not come on nowhere near as frequently.


-----Original Message-----
From: schnowz [mailto:schnowz at] 
Sent: 18 March 2007 14:32
To: gpzlist at; Stephen Hampson
Subject: Re: internal pressure?

 Thanks guys.. Live and learn.. I wasn't familiar with this on bikes, only 
on autos
 Unless you have a vacum leak or exhaust popping I don't see the point in 
removing it though....being as it's not gonna increase performance...

 Pete S
Commie EnvironMENTAList Bastard

----- Original Message ----- 
From: "Stephen Hampson" <shampson at>
To: "'schnowz'" <schnowz at>
Sent: Sunday, March 18, 2007 5:15 AM
Subject: FW: internal pressure?

> Hi, Steve Northrop explains it better I could see below.
> Cheers
> Steve
> -----Original Message-----
> From: Steve Northrop [mailto:blackgpz at]
> Sent: 17 March 2007 22:54
> To: gpzlist at
> Subject: Re: internal pressure?
> The KLEEN air system is a passive air injection system.  Air is drawn from
> the airbox, through the reed valves in the valve cover, through four
> passages in the cylinder head. This passage is the small circular opening
> right next to the spark plug with the hollow roll pin in it you can see 
> when
> you have the valve cover off. Each passage leads to an opening in the
> exhaust port. The venturi effect of the exhaust gasses passing this 
> opening
> is what draws the air in. This is why it is important to make sure the
> "figure 8" gaskets are in good shape. Whether the KLEEN air system is 
> intact
> or if the reed valves have been blocked off, a low pressure area exists 
> such
> that if it is not sealed well beneath the valve cover, oil can be sucked
> into the exhaust. I tapped the passages and epoxied in some 1/8 pipe 
> plugs.
> The PCV system is the hose that comes out of the rectangular cover at the
> back of the engine above the transmission. Remember the crankcase is open 
> to
> the transmission so it vents both.
> Steve in Western NY
> '96 GPZ1100
> '02 Daytona 955i
> "You Can't Fix Stupid", Ron White
> ----- Original Message ----- 
> From: "schnowz" <schnowz at>
> To: <gpzlist at>
> Sent: Saturday, March 17, 2007 7:15 PM
> Subject: Re: internal pressure?
>> Steve,
>> I'm not understanding this,where is it connected to the exhaust port?
>> The diagram shows it connected to the airbox, inlet manifold, and rocker
>> cover.
>> I thought it was acting similar to a PCV valve???
>>  Pete S
>>> From: "Steve Northrop" <blackgpz at>
>>> Subject: Re: internal pressure?
>>> To: "GPZ LIST" <gpzlist at>
>>> Message-ID: <000c01c7680b$a0467710$6900a8c0 at DB3HB511>
>>> Content-Type: text/plain; format=flowed; charset="iso-8859-1";
>>> reply-type=original
>>> Dave,
>>>     The absence or presence of the KLEEN Air system has no bearing
>>> whatsoever on jetting. This passive system introduces air at the exhaust
>>> port, it does not add any additional air to the engine. Blocking off the
>>> reed valves is no problem because they have nothing to do with venting
>>> internal pressure to begin with. This vent is at the rear of the engine
>>> above the transmission with a hose that goes to the airbox if you are
>>> still
>>> using one. The reed valves in the KLEEN Air system act as one-way valves
>>> so
>>> when exhaust gasses pass by the opening in the exhaust port, it will 
>>> draw
>>> some air with it. The reed valves keep exhaust reversion pulses from
>>> pushing
>>> exhaust gas back through the system. Sorry, but putting it back on was a
>>> lot
>>> of work for nothing.
>>> Steve in Western NY
> -- 
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