Idle rpm

[rollingpinz]

Hello

I just installed an SAV tach and at idle it reads 750. Is that normal? It’s been 15 years since I’ve had a pinz and even then, it didn’t have a tach.
My gut says it feels a little high.

[pcolette]

I've run my various Pinz's between 750 and 900 rpm depending on type of ignition (stock, Pertronix or PinzSSI). No problems encountered.

[ChickenPinz]

I'd use an optical (reflective) tach to verify the RPM as many of those dashboard gauge tachs aren't super accurate. The reflective tachs are pretty cheap, too.

[rollingpinz]

So my idle has been creeping up lately. It used to be between 750 and 1 grand, but it’s been hitting 1,100 or even 1,300 yesterday.
I’ve had all I can stands and I can’t stands no more. I did some digging and saw comments about the choke not closing all the way and solenoids.
It turns out that when I push the choke knob down, it bounces (slowly) up about 1/16 of an inch. I checked the choke levers and they’re parallel and almost 2 o’clock. I lubed the cable and cycled it a few times. No change. I’m not convinced that it’s enough to affect idle, so I checked the solenoids.
Sure enough, #2 was loose. I was able to turn it 2 full turns in.
That was it. It idles back at 1,000 and if I blimp the throttle, it goes down to 750.
Hope this helps someone with diagnosis

[ChickenPinz]

Okay, lots to unpack here.

First, you MUST have your timing set correctly. If the timing is wrong, it'll idle at the wrong speed.

Second, check your idle speed with the throttle linkage to the pedal disconnected at the carbs. Just pull off those short (6in?) connecting rods with the swivels on the ends. You want to ensure the linkage is moving freely.

Thirdly, mine tends to hang on idle, despite lots of investigation. A throttle blip and it idles down.

Fourth, my tach (Sun Super Tach II for the win!) reads high, so check your calibration with a reflective tachometer. You can get 'em on Amazon pretty cheap -- don't trust your analog tach until you check it. $20 https://a.co/d/3koARDW

[rollingpinz]

I’ll try that tach. Thanks for the link

[rollingpinz]

The reflective tach came today. With the engine idling at 1,000 on the dash tach, the reflective showed 1,090.
I know I need to check the timing.
Is there a timing light you recommend?

[ChickenPinz]

I can't recommend a timing light as I've had mine since the 1980's.

Nicer newer ones will tell you timing and dwell -- mine just flashes. I'd get a nicer one if I had to buy a replacement.

Keep in mind that if you have the OEM plug wires, you'll need to undo one and add a short temporary length of unshielded wire so your inductive clamp can sense the spark. The OEM wires are shielded, and my light's inductive pick-up won't see the spark. Maybe fancier setups can pick up the signals, but mine can't.

Don't sweat the 12V/24V thing -- I just use a small 12V battery to power mine and that's easier than finding a place to grab power from the engine.

[rollingpinz]

I’m curious. I have a 3-cell lipo(11.1volts) for my rc truck. Could I use that to power the timing light?

[ChickenPinz]

I would expect most timing lights to be fine with 11V -- you can check the specs on the model you want to be sure.

One fancy one says: "Power Requirements: 10 to 16 volts DC"