Design considerations

With the intention of leaving the bodywork “standard” most off-the-shelf air-filters must be dismissed and with the reluctance to modify the bodywork it leaves one option – make a air-box.

An air-box is simply that, a box of air. In this case it’s something that will sit on the front of the carbs delivering filtered air with the filter sitting somewhere else under the bonnet connected by a ram-pipe or the like. The major problem is getting smooth air-flow into the carb mouth, not an easy feat with the space I had and the 90degree angle. The main requirements of an air-box are:

  • Smooth transition into the carb mouth,
  • rounded edge to ease the air round rather than a straight edge which cuts it
  • long barrel to ensure all fluctuations in the air are lost.
  • Must have at least 20mm free space between the carb mouth (or ram) & the filter.

You can buy rams off the shelf easily which will do the above job, they cost around �10 and would do the job perfectly, but again they are too long for this setup – I wouldn’t be able to add filters onto the ends.

The easiest solution by far would be to simply bolt a plenum chamber on which married up to the entrance to the carb and not worry about the Ram tuning, or air turbulence inside but that might be detrimental to the potential power and indeed in the worse case scenario mike significantly lower power output by starving the engine of air. It has to be done right.