Drilling jet procedure

This is the best possible scenario. No drilling. No trusting of rebuild kit needles. No aftermarket jets. All changes can be undone

Drilling seems a workaround as jets are calibrated by flowrate rather than orifice diameter.
Flowrate should be a function of diameter, but fluid dynamics is a bit of a black art as many cylinder head porters have noticed.

Maybe a test rig could be constructed to see the actual flow rate in cc/min?

No worries Dave, I figured as much, which is why I added the wink. Your advice is still the best option if it is an option.

Brendan, the jets in question are actually numbered according to diameter, but you are right, as my TK22 site illustrates about the various main jet manufaturers, there are many other factors besides the simple diameter of the orifice. Anyone doing jetting would do best to stay with one brand of main jets if they are doing jetting by seat of the pants. That way, they know a bigger number is indeed more flow. With the wideband setup, it doesn't matter if you run apples against oranges, because the o2 sensor will simply tell you, immediately, exactly how rich or lean you are... very convenient.

Lou I repair lawn and garden equipment for a living and the EPA has this stuff running so lean
it's borderline burning itself up and with no other jets available I do drill jets at times but I use a hand drill.
I also use a torch tip cleaner that acts as a round file to clean and slightly open up jets

Yeah, I sometimes use the torch tip cleaners that way too. The drill I use is really cheap, but it has speed control down to less than 1 rev per second, and the chuck goes almost down to zero. Most chucks won't hold a bit as small as we use. It was just interesting that the cheapest drill available ended up being the best. Don't get that kind of luck too often.

Lou, would you expect anything different from a company based in the great state just north of you?

Hopefully menards 1. Still carries the drill and 2. Mfg or specs of that drill haven't changed since you found it a few years back

It may look different. I think the Tool Shop brand has gray tools now? And yes, hopefully it functions the same. 10 years ago it was $10. I didn't use it much until I realized it was perfect for jets.

EDIT: I checked Menard's website. Looks like they have an updated version online (appears to be red again), but I don't know if the chuck is the same. Hopefully they will have one in the store you can check out. The price has skyrocketed to $20.

Woah 100% lol. Better wait for my %11 sale period so I can save $2 lol

Alright. The plot thickens. Maybe. I got my drill bit set in the mail and for the heck of it I decided to gauge my main jets that I have laying around. (Extras). The #64 bit which should be just a hair less than a #92 jet WOULD not fit. All 4 of them. Now these jets are stamped 92. The next smaller bit was loose. Safe to say just the normal variation in bit/jet diameters? It wouldn't take much drilling to pop it through. But no amount of gentle wiggling will pass it through. I thought it'd be on the loose side since it's a hair smaller than the 92 jet id.

Yes, the bits do vary a tiny bit. I always mic them to get a better measure of the diameter. I try to keep a record of the jets to the nearest tenth of a mm. Sometimes half a mm can make a difference on the wideband (but probably won't be felt in the running).

Well, I may have some disappointing news. But maybe there is a silver lining. An ex-machinist I work measured my new drill bit set for me today... my #64 bit, which should be a hair less than a 92 jet showed up as a 99 jet. Now, that seems like alot of variation. Our mic here has seen better days, so he was using some high end caliper, which I am hoping just plain ol isn't that accurate. He's bringing his personal mic in tomorrow to measure them for me.

So, either the caliper isn't accurate enough, the bits vary widly, or somehow they are mixed up in the little sliding tray they come in. I made sure not to mix them up, plus you can only take one out at a time - kind of a neat little carrying case.

The difference is so small my caliper won't read them.
Steve

Forget calipers. High quality mics only, for stuff that small and precise. I've never seen any that far off.