I have guys running 4 X 3.4 mm holes in the slider. If I remember correctly it was a 3.4 mm drill bit. Drill the holes the same size as the existing holes. They all said it helped low down power and midrange power up to about 4000 RPM. after 4000 RPM it does not add any benefit over the stock holes. It also does not add HP to the top end.

Now where to drill these holes? Think of the 4 on a dice. You have two holes already. Drill the others in the same way as the dice layout. The must mirror the existing holes. You need to measure them exactly the same distance as the other two. Inside the slider there are supports. If you drill the holes wrong you are going to drill into the supports inside the slider. The placing of the holes need to be exact.

This is how it works. A vacuum carb will only open the slider according to the amount of airflow thru the carb. The butterfly can be fully open, but at low RPM the slider will not be fully open. So the more you can open it at a lower RPM, the more airflow you can get thru the carb and the more power the motor makes. The slider changes height according to the RPM and the increased airflow at higher revs. The extra holes helps create a stronger vacuum above the slider. The stronger vacuum helps the slider to open quicker and larger with less throttle opening.

Please don't go drill more or bigger holes than specified. If you drill the holes to big, there will be too little vacuum and you are going to caused problems.

PS... All this info is coming from a guy riding a raptor. It’s about time someone tells you how to tune carbs correctly. Raptor owners have two carbs to work on, so we get double the practice of DS guys. [img]i/expressions/face-icon-small-wink.gif[/img]