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S2 Dellortos/Airbox Configuration

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Hello All,


I have a Federal S2 which I am planning to fit with Dellortos.  I acquired a set of DHLA 45's and an original Airbox from a fellow owner in the UK some time ago.  I've since rebuilt the Dellortos but have  noticed there were no trumpets (aka ram pipes, air horns) included with the carbs.  Are the trumpets supposed to be mounted on the carbs or are they omitted with the standard airbox ?  I realize the Parts Diagram shows them but I'm not entirely certain I understand what benefit they provide.  Can anyone elaborate ?


Also, if they are supposed to be installed, is it correct to install them such that the airbox body is sandwiched between the flanges on the trumpets and the carb body ?  If anyone can also confirm the length of the trumpets that would be very helpful as well (I suspect that 60mm is correct).


Many thanks for any advice.


Lou R 

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Hi Lou,


Can't measure the trumpets for you are mine are fitted and the early S1 screw down airbox cover is a bitch to remove/replace!  You are correct that the airbox body is sandwiched between the carb faces and the trumpet flange face. Their purpose, as I understand it, is to 'tune' the airflow into the carb - they are important to fit and the length makes a difference.  


Here is a photo of mine.




Cheers - Jon.

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Thanks for the photo.  After studying it I'm thinking the 60mm trumpets I thought would be correct might be a bit too long.  Even though they will meet the recommended 25mm clearance they still seem long compared to those in your photo.  I know that replacement trumpets are also available in 40mm and 48mm lengths (among others).  A little further research indicates the shorter trumpets are used in high RPM applications and the longer ones are better for street use.  I'll wait a little longer in the event someone can provide a trumpet length as per the original specification.  If I can't get any further advice I'll take a stab at either the 40mm or 48mm versions.


Thanks again for the help.

Lou R

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Thanks for the confirmation.  I'm pretty sure the S2 has the same induction parts as the S2.2 so going with the 48mm trumpets will keep it as it left the factory.


Thanks again,

Lou R

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