More drilling of motorcycle bits

I find I have #35 slow jets and need #40.
Are carburetor jets sized in a standard way?
These are kehein carbs.
Reply to
jtaylor
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Keihin carb jet sizes are typically numbers that refelect the orifice size in hundreths of mms. Therefore a #40 has an orfice size of 0.40mm.
Reply to
Peter Snell
Buy the jets. You will be unable to drill them and get the correct flow characteristics of the factory jets.
Jim
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Reply to
jim rozen
Why is that?
Is it something other than a straight hole?
Reply to
jtaylor
In the case of Holley jets they are flow tested after mfg. and then sized. The radius into the jet will affect the flow, as well as how round you drill the hole, and the surface finish through the bore. In Holleys case you can drill a 35 to a 40 but it may not flow the same as a factory 40. So theres more to the game than just the size of the hole. lg no neat sig line
Reply to
larry g
The ones that I've seen had the edges broken or champhered. Get the top edge the slightest bit crooked and that screws up the flow pattern, just like a burr on the muzzle of a rifle destroys accuracy by throwing the bullet off to one side. Buy new to get it right
Reply to
GMasterman
Ok, I'm convinced. Hope they are cheap...I might get unconvinced...
Reply to
jtaylor
not sure what your riding, but assuming it's a harley evo, here's a link to a site that carries jets.
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not, it will give you an idea of cost. good luck, walt
Reply to
wallster
Go price them, you may be pleasantly suprised. Compare that with the hassle of trying to rejet reproducibly when the 'size' of the hole does not reliabley relate to the flow.
Jim
================================================== please reply to: JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com ==================================================
Reply to
jim rozen
I realize that this is not the question that was initially posed, but the comment may have some bearing on the subject.
Holley jet sizes are an indication of a relative size, not necessarily a drill sizing system. Check them with a set of pin gages and find that they are not the same diameter, so are probably put on a flowbench of some type. Maxxjet (for Holley carbs) are a little truer to having a more consistent diameter for a stated jet size.
jim rozen wrote:
Reply to
nic

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