Next you lot will be holding workshop days :smile You can't beat first hand experiences and knowledge handed down the line and helping others. The ones learning then learn and when capable/confident of doing something themsleves can then pass the skills on to the next one with lessor knowledge.

The air bleeds are an interesting one. Air bleeds, bleed off the vacuum that draws the fuel through the fuel jets. IIRC A larger air bleed leans the mixture and a smaller richens it up.

Interesting how different jet kits deal with them. The FP race kit ( their high end jet kit CRB-H77-1.7-RK) comes with two different size drill bit's to enlarge the main air bleed.
1.4 (front) Drill Bit (for enlarging stock main air jet)
1.1 (rear) Drill Bit (for enlarging stock main air jet)

HRC have a cap to cap it off totally for when running with open airbox. This then require smaller mains, a lot smaller as capping it off has richened things up.

Neither of these are the same as a flow commander though as it's a fixed change and a flow commander is adjustable, but interestingly enough the flow commander uses the main air bleed. Maybe this works on the principle of opening up and closing off the main air bleed. Richens or leans!!! A bit like how a camera aperture works.

There's also the Emulsion tubes to consider as these are different front to rear. Factory Pro say that if your suffer from persistent over richness then replace the front one with another rear one.


Note the position of the holes, front being closer to the bottom of the tube, so sunk further into the fuel.

The air from the air bleed enters the mains through the emulsion tube. The emulsion tube has a series of small holes from top to bottom, and it is through these holes air enters the main circuit. At low engine speeds, when fuel demand is low, these holes are submerged in fuel, and so no air can flow through them. As engine speed increases, the fuel level in the float bowl drops therefore uncovering these holes. This then allows air from the bleeds to enter the main circuit which leans off the mix. As engine speed increases the fuel level in the float bowl continues to drop which then uncovers even more of the holes in the emulsion tube, which makes the air bleed have a greater effect on the mixture.:think something like that anyway LOL

Carbs can be as easy or complicated as you want to make them. Also note the holes lower down in the carb throat from the pilot circuit that keeps the bike ticking over (idling) with the throttle plate (butterfly flap) fully closed.

Oh and It should be noted that there is an air bleed for the main circuit and pilot circuit on top of the carbs. The needle circuit is controlled by the slide lift holes.

(:-})