Engine speed throbs

hi pamela.
Throbbing from vascular origin
A vein can produce this sensation because of the increased blood flow to a particular area due to physical activity - this can happened when you jog in the morning or after bodybuilding exercise or any other physical activity. When somebody tackles you during a football game and traumatizes your leg, the swelling can push on the vessels and this can produce a throbbing sensation. A trauma can also produce an abnormal communication between an artery and vein - this is called AV fistula.
Usually throbbing from vascular origin is not a reason to worry. You may visit a general practitioner who will probably examine the blood flow and may even order a test to look at your vessels.
Rarely the cause of throbbing is aneurism which produces a wide pulsatile area - aneurisms are often treated surgically.

• It is useful to know that common conditions such as deep vein thrombosis, blood clots or peripheral artery disease usually do NOT present with throbbing sensation but usually present with pain and swelling.

Throbbing caused by muscle twitching
Turn off the lights, sit on a chair and use a direct light from a lamp and try to make the light beam horizontal so you can see the throbbing area clearly.
If you see tiny twitches you should know that your throbbing sensation is produced by your muscles.
Conditions causing muscle twitching
Although muscle twitches are often idiopathic or as a result of muscle hyperactivity or hyperexcitability because you had too much coffee or you had a heavy exercise earlier, muscle twitches can be a symptom of a serious medical conditions.
B12 deficiency. This is found especially in alcoholics or vegetarians. Muscle twitching is not an early symptom, usually B12 deficiency presents with anemia and decreased or altered sensation.
Multiple Sclerosis. Usually presents with pain behind one eye. Muscle twitching is a common symptom.
infection and Amyotophic Lateral Sclerosis also known to cause muscle twitches. It is advisable to see a neurologist for further evaluation, the neurologist is most likely to order MRI and blood test
read up more at this link.

https://www.steadyhealth.com/medical-answers/causes-of-throbbing-or-pulsing-sensation-in-arms-or-legs
Understanding Symptoms of Aneurysm
https://www.steadyhealth.com/topics/strange-throbbing-pulsing-in-my-thigh-just-above-knee?page=2
what is the cause of Pulsating in my leg Google Search

Fuel starved, carb should have an idle adjustment which sounds like it is fine. Look for the second adjustment

1. Fault Phenomenon

The crankshaft rotation speed is normal when starting, but it takes a long time to start, or there are obvious signs that the crankshaft can't start.

2. Failure Cause

Air leakage in intake system; low fuel pressure; clogging of air filter ; fault of water temperature sensor; malfunction of air Flowmeter; failure of idle speed control valve or additional air valve; failure of cold start injector; leak of injector; Incorrect ignition timing; starting switch to computer connection broken; cylinder compression pressure is too low.

3. Fault Diagnosis and Troubleshooting

A. Perform fault self-diagnosis. If there is a fault code, by the fault code to find the corresponding cause of failure.

B. Check the vacuum of the inlet during idling. If the vacuum degree is less than 667 kPa, the air leakage in the intake system should be checked at the joints, gaskets, vacuum hoses, exhaust gas recirculation system and fuel evaporation recovery system.

C. Check the air filter. If there is a filter plug, it should be cleaned or replaced.

D. If the engine can start normally when the throttle is about 1 / 4 open, and if the throttle is difficult to start when the throttle is completely closed, the idle speed control valve and the additional air valve should be checked to see if the idle speed control valve and the additional air valve are working properly. In cold car idling operation, unplug idle control valve harness or clamp the additional air valve hose with pliers during idle running. If engine speed does not decrease, idle speed control valve does not work properly. Idle speed control valve and its control circuit should be checked.

E. Check fuel pressure. Use a wire to short the two test sockets of the electric gasoline pump, then turn on the ignition switch to make the electric gasoline pump run. In this condition, the fuel pressure should be about 300 kPa. If the pressure is too low, check the oil pressure regulator for oil leakage, gasoline filter plug, gasoline pump maximum pump oil pressure is normal.

The governor regulates the engine speed and when a load is applied that would slow the engine it is the governor's job to open the throttle to maintain the speed. It also limits the maximum engine speed to a safe level. As a user of the machine you should have formed an idea about whether the governor is working correctly.

If the governor linkage moves freely against the spring(s) and the maximum revs of the engine are about right no adjustment should be attempted and the fault probably lies elsewhere, most likely fuel starvation though bad ignition or valve timing, tight valve clearances or partially blocked exhaust can affect power output.

A back-to-basics approach is usually the best if the problem has built gradually but if it happened suddenly I suggest you begin by thoroughly cleaning the carb.

This is fuel starvation, check inline filters, check the brather in the filler cap, remove float bowl and blow out main jet with air line.

Inspect the wheel hubs for flaws in the rotor mounting surfaces that could prevent rotors from seating properly. Also, check the wheel bearings for slop, roughness or other signs of wear. If the bearing does not rotate smoothly and keep the rotor on center, the rotor will wear unevenly. (Also, pay attention to unusual rumbling sounds when cornering or sudden jerks while braking; these indicate possible wheel bearing problems. The jerking may be caused by the bearing locking up momentarily when the brake changes it load forces.)

Another thing to look at if the problem recurs: take a quick peek at the instrument panel to see if the low traction warning is on. If it is and the road conditions are good, the anti-lock braking system has a false trigger condition. This could be caused by an off-center rotor or a sensor fault. The hard part is identifying which wheel has the problem

Check your wires and spark plugs. If it is carburated engine check your air filter and vacum hoses.

I would have the voltage regulator tested. It is on the altenator. Most part stores will test it for free in or out of the vehicle. When this wears out, voltage fluctuates in the system and does not stay steady.

Surging engines in lawn mowers are usually related to a lean fuel/air mixture. With today's environmental concerns, the carburetors on these engines are set with a very lean mixture (to reduce air pollution). Furthermore, they usually put limiter caps on the carburetors where you cannot easily adjust the mix to get the engine to run better.

If there are adjustment screws on the carburetor, try turning the high speed adjustment screw a bit counter-clockwise (if the limiter cap will allow it). This will enrich the fuel/air mix a bit and might help the engine run a bit better.

Sounds like you may have a worn out CV joint and the clicking may stop with an oil change. Good Luck