what do the wee drills drill.out in carb kits...?

[Seana23]

Jus wondering...
Seen a carb kit and it included a tiny drill bit....
What.is this used to do?

Thanx.
Xxx

[Guest]

Which kit?
With Dynojet kits the smaller bit drills out the port in the slide. The larger is for removing the USA cap over the idle mixture screw.

[Wizard]

On some kits the drill is for the CV Carb Slider Vent Hole, makes it bigger.
A small hole means the slider will rise slow, so no matter how fast you whack the throttle, the engine won't spin up too fast.
For a snappier response, drill the Slider Vent Hole larger.

[kdo58]

the hole is not straight down, you have to drill at a slight angle.

[Seana23]

On some kits the drill is for the CV Carb Slider Vent Hole, makes it bigger.

For a snappier response, drill the Slider Vent Hole larger.

Is that the tiny hole on the base ov the CV piston next to the needle...?

Xxx

[Wizard]

Not sure what your slider looks like, but if its a hole that goes clear right thru and seems to have no purpose, that it.
When I did the measuring (use a drill set to slide small drills thru, get the original hole size), the new drill increases the hole AREA by 50 to 100%.
The increase is a PI-R-squared thing, so its not a doubling of diameter.
You'll have to do the arithmetic
I lent my Stage One Kit drill to STJohn who did not install a DynaJet Kit, but did want the throttle snapiness, so he drilled out his Vacuum Lift Vent Holes (carbs were very similar (84 VF1000F/84 Saber1100)).

[Wizard]

Couldn't rember what my Needles were set to (installed in 1990, and I didn't write it down), so I took one Carb Cap off.
My CV pistons have 2 vent holes, and some Carbs can even have 3.
My Honda vent holes were vertical (not on angle).
My needles are at the Leanest position,,.. this bike was set Very Rich from factory (Calgary = 3300').

[GateKeeper]

Is that the tiny hole on the base ov the CV piston next to the needle...?

Xxx

yes

[Spyder]

Interesting. And what would happen if this hole is drilled a bit too big?
Are there any other mods that need to be made with this one?
What are the pro's, and con's attached to this mod?

[Wizard]

The drill size will depend on whether you install the Stage 1,2 or 3 kit.
Too big and the beating manifold vacuum from the cylinder sucking can bias it. Throttle might be too touchy.
No other mods needed, a standalone mod.
Pro's? Snappy throttle response.
Cons? Snappy throttle response.
I was riding to work one morning when I whacked the throttle to make a lane change, and the bike turned sideways on me,,.. was frost on the road, hard to see.
Didn't fall, but I sure needed that first coffee (and a change of shorts,,..). Be careful what you wish for,,..
If your bike performs fine for your needs, leave it alone.
I installed a DynaJet Stage 1 kit cause the bike was jetted stupid rich from factory, and there was no adjusting the needle.
I went down a lot on the main jet and the needle is all the way down (lean as it gets). Here we ride 3000 to 6000' and its cooler.
Most bikes will get the biggest punch by getting the jetting right for your altitude/temperature.