Airone Sport with SS25 carb

[Don-Spada]

Hi  

I have a 1953 Airone sport with the original SS25 carb fitted.  It has always run very rich.  It will start easily without any need to tickle the carb, if I do it fouls the plug.   The carb is generally in good condition, my friend made a new slide that fits well in the body as the old one was very worn. 

I was reading an old thread in the group recently talking about the idle mixture screw.  The owners bike had similar problems to mine, running rich.  His had a rubber bung over the hole on the left side of the carb which seemed to be the cause of his problems.   

 

Backfire on Kick start   

Looking at my carb, that hole has a brass plug screwed into the hole opposite the idle screw.  It looks authentic, it fits nicely, but the past conversation I was reading suggested that this should actually be an open hole to provide the air for the idle circuit.  See photos attached with the screw fitted and with it removed.  The air screw on the right side does seem to have a slight effect, the engine dies if I screw it right in or well out.  

My question is should this be an open hole or should it be capped off?  Can someone share a similar photo of the carb on a well running Airone sport     

Many thanks 

Don West  in the UK.  

[jef walker]

Hi Don,

This is a picture of my Airone sport 1953, it's blanked off on mine and runs very well.

Hope this helps.

Regards 

Jef Walker 

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From: 'Don-Spada' via Guzzi Singles <guzzi-...@googlegroups.com>
Sent: Monday, April 13, 2026 5:15:08 PM
To: Guzzi Singles <guzzi-...@googlegroups.com>
Subject: [guzzi-singles] Airone Sport with SS25 carb

 

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[Don West]

Thanks Jeff.  It's strange why the previous conversation suggested that this should be an open air hole?  

Don  

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[RICHARD YAMANE]

I have a similar port on my GTV carb. I thought it should have been plugged but was told that it is supposed to be open. My carb will drip a bit of fuel from the port which is why I thought it should be plugged. 

Rick Yamane
Importer of Vape/Powerdynamo ignition systems and Polisher of bikes at Motion Pro

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[John O Regan]

HI All,

The hole opposite the pilot mixture is the pilot air inlet, 

Over time the incoming air  gathers road dirt which will affect the slow speed running 

It should be occasionally be cleaned, make a note of the number of turns from fully closed the pilot screw is

then remove it and flush through with carb cleaner, replace the pilot screw to the same position before any adjustments

John

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