How are main jets sized?
A jet is 0.35mm in diameter. For Keihin Carbs, the dimensions of the jets refer to the diameter of the measuring hole, expressed in millimetres. A 100-mm jet is 1.00 mm in diameter. A 38-mm jet is 0.38 mm in diameter.
Are all Keihin Jets the same?
No they aren’t all the same they have a few different ones. My ktm dealer had all different kinds for keihin carbs. I’d say they should have what you need.
How do I know if my pilot jet is too small?
If the bike surges or hunts, the pilot jet is probably too small (lean). Other indications that the pilot circuit is lean are popping or spitting through the carburetor when the throttle is opened and popping or backfiring through the exhaust when the throttle is shut.
How is the size of a jet determined?
Jets are threaded and have a small orifice through their center that varies based on the size of the jet. For example, a jet may be stamped (on its head) with the number 30. This indicates that the jet’s size is 30 mm.
When do you need a larger main jet?
If the engine gains power as you roll the throttle off, then the main jet is too small and you need to fit a larger one. If the engine staggers slightly or has a hard hesitation, then the main jet is too large and you need to fit a smaller one.
What does the number 30 mean on a jet engine?
Jets are threaded and have a small orifice through their center that varies based on the size of the jet. For example, a jet may be stamped (on its head) with the number 30. This indicates that the jet’s size is 30 mm. Installing a smaller size jet will reduce fuel flow, which is ideal for high-altitude…
When do you need to change jet sizing?
If the engine shows performance problems such as stalling or sluggish acceleration, you’ll need to change the jet sizing. Jets are threaded and have a small orifice through their center that varies based on the size of the jet. For example, a jet may be stamped (on its head) with the number 30.
If the engine gains power as you roll the throttle off, then the main jet is too small and you need to fit a larger one. If the engine staggers slightly or has a hard hesitation, then the main jet is too large and you need to fit a smaller one.
How big of a drill bit do I need to drill a main jet?
If your stock main jet is a 100 (stock size in a 22mm Mikuni) you will find this jet size falls between the #62 & #60 drill bit. Run the engine with the stock main jet and take a plug reading. If it’s lean and you need to increase the size of your main jet, drill the jet out with the next size larger drill bit,…
How to compare Mikuni and Dynojet Jets?
Question, I have some dynojets and would like to purchase Jets R Us jets, how do I compare the sizes? Dynojet does not produce hex jets, only round and therefore dynojet provides a main jet adapter. Because dynojets are not manufactured 100% the same as mikuni and keihin there is not an exact comparison between the two, flow rate may be different.
What kind of jet do I need for a 34pict / 3 engine?
Assuming a vacuum distributor, the 34PICT/3 carburetor is usually jetted with a X127.5 main jet, and 100Z -120Z air correction jet. For the 1600cc engine, you need more fuel flow, so a larger X127.5 main jet and 100Z or 120Z air correction jet are needed.