The bike is a Hero Honda Splendor Plus. When riding the bike I noticed a "Tshch" sound which I estimate happens immediately after the compression stroke of the engine. I took the bike to a local mechanic who removed a couple of tubes near the engine while having the engine running, but he couldn't figure out what the problem was. He did say that it seemed like there was an air leak somewhere and that it would go away after I rode the bike for a while. After riding the bike for a while it did seem like the sound stopped, so I assume it was because of any of the metal pipe's shrinkage during winter which gave some gap for air to leak.
Today morning I noticed that when I raised the kickstart lever to start the bike, if I just pushed the lever down by 2 centimeter with my foot, I could hear the "Tshch" sound from somewhere near the engine. Brought the lever back up and moved it 2cm down and the sound could be heard again.
Service centers tend to inflate bills and give bogus reasons, so I wanted to know what the problem might be before taking it to an authorized service center.
Also because the local mechanic didn't have a clue as to what the problem was.
What in your opinion might be the possible causes of such a problem? Images of the engine area are here: Troubleshooting fluid leakage onto the engine area?
Removed the spark plug and fitted it back as per the user manual. The sound persists. This time I moved the kickstart pedal with my hand and positioned my ear near the engine. The sound persists, and it's not from near the spark plug area.
I can see why the mechanic couldn't figure it out. It's hard to locate the source. At first the sound seemed to come from point1 in the picture. Then it seemed to be from point2. Then it seemed to come from the general area between 1, 2, 3 and 4. I need to debug this like how I debug software. Is it safe to yank out any of these tubes, plug them with my finger and push the kickstart pedal to check if the sound still exists?