in progress...
 

 
Extended Tube in the XR1200 Airbox
 

 
Experiments with velocity tubes on the XR1200 throttle body show that significant improvements in TQ can be had with intake tuning.  This modification will incorporate an extended intake tube inside the OEM airbox to see the effects on TQ/HP.
 
 

 
Extended Tube in Airbox
 

 
To make this modified air intake tube, I custom fit a section of a 2" right-angle, rubber tube to a rubber mounting boot for the airbox.  Externally, this is what the tube looks like.  Internally it is a smooth flow from the 2" (50.8 mm) tube, into the 50 mm throttle body.
 

1Elbow.JPG

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The intake boot, modified with the elbow, replaces the stock rubber flange that attaches the intake to the bottom of the airbox.  The picture to the right shows what the intake tube looks like, installed on the bottom half of the airbox.
 
 
 
 
 
 
 
 
 
 
 
 
 

2Grommet.JPG

 
 
 
 
 
 
 
 
For comparison, the picture to the left shows the stock rubber bushing installed in the bottom of the airbox.
 
 
 
 
 
 
 
 
 
 
 
 
 

 
 
 
 
The below picture is a look at the air intake tube through the opening for the air filter. 
 
 
This airbox has been modified to remove the mounting box for the intake flapper valve that is in International versions of the XR1200, to remove some of the plastic bosses that are in the flow of the air path, and to enlarge the air filter opening.
 
Later I will check to see whether this intake tube fits into a stock airbox.  I suspect that at least part of the flapper valve mounting box will need to be removed to be able to put the tube in place.
 
 
 
 

4Elbowinstalled.JPG

 
Installing the airbox on the throttle body is just a little harder than usual, but if a little lubricant is placed on the outer edge of the throttle body, the rubber boot can be fit around the throttle body as the airbox is put in place. Once the airbox is installed, the modification can not be seen.
 

 
Conclusion
 

 
 
Once I have dyno numbers for my bike comparing the TQ/HP with this tube to that using the stock rubber mounting grommet, I'll send the tube over to a friend to see whether it has any impact on a stock XR1200 engine.
 
 

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