Used jets
This article is about buying or borrowing used jets. When jetting carbs often it is easy to go to a local shop and get a cheap used jet from the dealers use jet bin. The first problem is that no information is known about the jets. They could be drilled out, varnished up, damaged orifice due to unknown cleaning methods. Those are just the first obvious pitfalls. The second issue is that even if the jets have never been tampered with, the jets in the bins could have come from hundreds of manufacturers.
What happens if the jets are from multiple manufacturers? For starters many manufacturers have their own special numbering system for jets. That means a 120 jet from company A does not match a 120 jet from company B. Most everyone knows that Dynojet has their own numbering system, and they are open about it. Now add that people clone dynojets improperly and it becomes obvious quickly that there could be a jetting nightmare. A 140 jet could run richer than a 180 jet depending on who made the jet and if it has been drilled out or not.
Another issue is a person who knows of issues and takes the time to look for jets stamped with Genuine markings. While it is a good effort, there are so many companies making FAKE jets that you cannot trust jets in a random parts bin.
When rejetting and going to larger and larger jets methodically, these variations will ruin results. It is just not worth spending a day or week etc trying to dial in a carb with mystery jets. While money can be saved with used jets, there are so many side effects, it seems like a poor place to try and save money.
If wanting to learn more about our Genuine vs OEM equivalent jets go to this link genuine vs oem.