The enrichener is covering a lean spot. This 1976 Honda CB500T would take a rev with that lever partly on, and it died with the lever off, or when the throttle was opened from about 1,000 rpm. The cable is a different fault. That one, the 8,000 rpm start, is the throttle-stop guide, and it was already fixed when this showed up.
The slow jet has not been pulled on this bike. What follows is the check order for the symptom it had, not a claim that a new jet cured it.
What the enrichener was covering
| What it did | On this bike | What it points at |
|---|---|---|
| Lever at half as soon as it fires | It preferred half over full | Full enrichener was already too much fuel |
| Lever off, or a rev from about 1,000 rpm | It died | The slow circuit is short of fuel |
| Right pipe, bike on the left stand, reserve | A light sputter | The high-side bowl was low. Judge it upright |
| Main jet | Not the circuit in use | A #145 main does not save a stumble off idle |
It is not a choke
On these Keihin CV carbs the lever does not close a plate over the air. It adds fuel through the enrichener circuit. The grip opens the butterfly immediately. The vacuum slide follows a moment later. The fuel for that gap comes from the slow jet and the passages around it. If the engine is cold, leaned over, or that jet is partly blocked, the enrichener is the only thing keeping it running.
Full lever is for lighting a cold engine. On this bike, half was better as soon as it caught. That is normal. Start at half if it has already been run, or if the air is mild. Use full only when it has gone cold and will not fire at half.
Stand it up before you judge it
The right exhaust sputtered while the bike was on the left kickstand, on reserve. The right carb is the high side in that lean, and its bowl runs low. Put it on the center stand. Turn the petcock to ON if there is fuel above the reserve pipe. Then listen again.
Warm it there with the enrichener partly on. A healthy CB500T on a mild day wants about a minute or two before the lever is fully off. A cold morning can take three or four. After about 30 seconds it should accept half lever. Once the fins are too hot to hold, it should sit near 1,100 rpm with the lever off and take a small rev without quitting. The oil and the cases take longer than that. Ride it gently for the first few miles instead of idling it until everything is heat-soaked.
If it still dies the moment the lever is closed after three or four minutes, the slow circuit is still short of fuel. Leave the mixture screws alone until it will idle hot and upright with the enrichener off. Turning them now just hides the blockage.
The #38 slow jet
The stock slow jet on a 1975-76 CB500T is a #38, Honda part 99124-292-0380. The main is a #145. Rebuild-kit listings, including the Keyster kit sold for this model, use those sizes, and Honda also cataloged #35 and #40 slow jets. Read the number on the jet that comes out of the carb before you order another one.
A blocked slow jet is cleaned, not drilled. Use the smallest wire that will pass, from a tip-cleaner set. A wire that is larger than the hole makes the jet richer forever. The passages in the body have to be clear too. A new jet in a gummed passage changes nothing. Buy the jet from a Honda specialist who will state the size, not from an anonymous listing with a part number and no size.
Carbs that have been off go back with the O-rings seated and the clamps actually tight. A clamp that looks tight and is biting only the rubber is how one carb walks out after a heat cycle. That leak is the runaway-idle fault in the other guide, and it is a poor match for an engine that idles and then dies when the extra fuel is taken away.