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EVguru
02-25-2011, 07:30 AM
With the high volatiles content of modern Petrol, I'm often having to lean out the idle circuit on bikes to get crisp running.

I don't have an extensive range of jets for testing and buying them for experimentation gets quite expensive after a while. Also more and more bits are not available for older Dellortos. I'm already having to modify one Atmoiser into another version.

It used to be easy to find sets of jet drills, but I just can't seem to find any these days. I need drills from say 0.35mm to 0.45mm by 0.01mm steps and suitable for drilling brass.

Any thoughts?

PixMan
02-25-2011, 07:52 AM
Titex has them. Their series A3143 HSS-Co Micro Precision drills are available in .01mm increments from .05mm to 1mm, then in .05mm steps to 1.45mm.

Their series A1211 HSS jobber drills also come in those .01mm size increments, from .20mm to 2.0mm, then bump up to the .05mm steps.

The A1211 are a regular jobber drill, and will be the cheapest per drill, but you have to buy in 10pc minimum packs.

The A3143 are a DIN-shank drill, and are sold in 5pc minimum packs. And those are generally twice the price of the A1211. I do believe the A3143 are the better choice though.

Highpower
02-25-2011, 07:56 AM
Do a search for local clock & watch repair suppliers, or search for "pivot drills". Those are used for drilling brass plates or bushings in clocks. I have a set of drills that go down to .004". :eek:

Here (http://www.clock-parts.com/catalog2.asp?GroupID=393&Level=3) is an example of what is available. Best of luck.

Willy
02-25-2011, 10:07 AM
I don't have an extensive range of jets for testing and buying them for experimentation gets quite expensive after a while.

An option I often use when I'm short on time or jets is to soft solder an existing jet closed.
This gives me a "blank" to experiment with, easy to drill and gives me any size I have drills for. Kind of a one size fits all jet without breaking the bank.

bruto
02-25-2011, 12:19 PM
A recommendation long ago from someone who drilled jets occasionally was to find a torch cleaning set of the sort that uses tiny drills rather than spiral wires. You get a little hand chuck and an assortment of very small drills. I should mention I have never tried drilling a jet with these, but it seems a good cheap possibility if the right sizes are present.

tylernt
02-25-2011, 01:05 PM
An option I often use when I'm short on time or jets is to soft solder an existing jet closed.
This gives me a "blank" to experiment with, easy to drill and gives me any size I have drills for. Kind of a one size fits all jet without breaking the bank.Interesting. Does a jet need any specific cross-section to work properly? I.e, does it need to be shaped like an hourglass and/or be a certain length from inlet to outlet? Seems like a long skinny straight-walled hole might have different flow characteristics than a short hourglass-shaped one of the same diameter, but I'm no expert.

cuslog
02-25-2011, 01:34 PM
I've been doing it on Holley carbs. Using brass set screws for blanks and number drills.
Drill and tap for 6,8 or 10-32 X 1/8".
I think Tylernt is correct about flow characteristics, but once you've made the switch over to straight thru, you can compensate.
I've been using an O2 meter as well, very handy tuning tool.
Check out innovatemotorsports.com

Willy
02-25-2011, 03:26 PM
Tylerent brings up an interesting question about the shape and length of a jet and it's flow characteristics.

I've always kept the distance of the jet's ID length as close to stock as possible so as not too restrict the flow, in addition I chamfer the edges too. I've also used tip cleaners as Bruto mentioned in order to sneak up on a size, using a micrometer to accurately measure size.
Of course just as a long garden hose flows less than a short one, a jet with a longer travel would flow less than a short one.
But if one does not achieve the desired results it's a simple matter to increase or decrease jet size, as it would be hard to quantify the flow characteristics without an elaborate set of instrumentation.

The O2 meter that Cuslog uses is of course the most accurate measure of one's progress, it at least gives the old "seat of the pants" or plug readings method an accurate reference point.