T500 throttle stop screw - initial setting

[jabcb]

Bought the T500 cafe build bike without carbs. (Incomplete project bike priced accordingly.)

Bought nice vapor blasted carbs. So there is no prior history for the settings on these carbs.

Spent a few minutes before dinner giving it a go.
A few kicks with the choke on + key off, and then with the key on will get it to run briefly but too slowly.

My initial throttle stop screw settings are a WAG.

Any suggestions for an initial setting? All the info I found is for adjusting the stop screw for a running engine.

[ConnerVT]

I assume by "Throttle Stop" you mean the idle speed screws? If so, sounds like you're close.

Since you say you can get it to start and run briefly, I'd give them another 1/2 turn in and try again. Lather, rinse, repeat as necessary.

Another thing I do is (once things seam like all can run well) is set the idle a little higher than you would normally (maybe 1200). Pull one spark plug wire, so running on one cylinder. Idle will drop. Set idle speed to where engine will idle at a steady RPM. Repeat for the other cylinder, set idle for the speed of the first.

With both cylinders running, idle will now be too high. Back both screws out equal amounts (maybe 1/8th - 1/4th turn at a time) until you get your desired idle speed. Both cylinders should be fairly balanced then.

[jabcb]

Thanks for the tip. Yes, it's the idle speed screw — the Suzuki parts manual calls it the throttle stop screw.

I found this video. He uses a method to set the stop screw that I hadn’t thought of. See 9:12 in the video.
https://www.youtube.com/watch?v=IGp_d1n6ar4

I had purchased another set of carbs. Used his wire method on those. And marked a cut-down 3x5 card as a measure tool for the filter-side of the slide. Compared that measurement to the carbs on the bike.
This confirmed your tip that the slides were too closed.

[ConnerVT]

Yeah, off the top of my head, I couldn't say what the gap would be, if any at all, for a "standard" T500 setup.

Since you said it was close to starting and running, figured juts adding a bit to both carbs might get you idling. If it is the first startup, it is best to start slow, and work your way up. Nobody wants to wake up an engine from a long sleep at 7500RPM.

[jabcb]

It’s a 73 T500, but with a GT500 motor that has PEI. My first exposure to PEI. The ignition fires both plugs every 180 degrees.

Started doing a few checks.
Carb fuel levels are good.

Removed both plugs & grounded them to the cylinder head. Hand operated the kick start & checked for spark.
Wasn’t expecting it, but moving the lever slowly by hand did not generate a spark.
Got a consistent spark for a quick lever motion.

PEI is a magneto CDI. The wiring is completely separate from the 12v DC circuitry.
Did a quick web search for “minimum rpm for magneto to work”. Got info about small planes & one about lawn movers. The article about lawn mowers said that the minimum is 250 rpm.