Surging idle on choke. Not running without.

The pilot jets are sized up to 145. With stock exhaust and stock air filters. 3 turns out on the mix screw. When full choke It runs super high rpm.

When I take it off choke it dies.
I feel like it's running lean. Any ideas ? Is the pilot screw too big ?

The pilot jet is not blocked. It was just cleaned. Same with the main jet .

Was running fine before you rejetted the carbs?

Pilot jets for stock bike are 42.5 and mains are 135. When the bike warms up on choke the idle will increase. Go to half choke then no choke. The bike should then idle at 1200 rpm's. Carbs synced with manometer? Post some pics of the bike.

Hi John, so I have similar symptoms, starts ok on choke, and when choke pushed in, but as it runs revs go higher and higher.
I think you may have got your jets mixed. The pilots will be 42.5 or 45 ish, mains around 135 -140 unless you have an SE when they are 125.
I think the 145 you are referring to could be a miss read, or you are looking at the pilot air jets at the carb inlet which are generally 150.

The air jets on the mouth of the carb should be 155 for the 80-82 sohc xs400 ( U.S.) Those should never be changed to tune the bike. Keep them stock size.

Gra900 said:

Hi John, so I have similar symptoms, starts ok on choke, and when choke pushed in, but as it runs revs go higher and higher.
I think you may have got your jets mixed. The pilots will be 42.5 or 45 ish, mains around 135 -140 unless you have an SE when they are 125.
I think the 145 you are referring to could be a miss read, or you are looking at the pilot air jets at the carb inlet which are generally 150.

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The pilot jet is a 45 . I made a typo

If you have stock exhaust and air filter 45 pilot jets are too big. Could be why it stalls at idle. Post pics of what your plugs look like.

Ok so I have two carb sets and switched back to the carb with stock pilot jets. I have stock exhaust. Stock air cleaners. I'm 3 turns out on the mix screw. And when I start it the idle still surges on choke. I was able to start it without choke eventually. And the idle seemed smoother but as soon as I twisted the throttle the idle went up and stayed up.

Definitely seems lean.

Check for air leaks. Have you synced the carbs with a manometer? It's very important to do this!!. Check the diaphragms for leaks. The carbs need to be cleaned very well including all the small passages even the ones in the bowls. Make sure your shaft seals are not leaking. Make sure the floats are set to 26mm without the bowl gasket on and do both sides of the float. Have you replaced the pilot jet rubber plugs? If your running a vacuum petcock make sure the vacuum line in not leaking. The pilot mic screws also have o-rings that go bad. Make sure the exhaust is leak free and that no one has drilled holes into the ends. Post some pics of what the plugs look like. Post some pics of the bike. If your fully stock the bike should not need larger jets.