Indian Four 1932 - problem with 3rd cylinder

Hello,

My name is Tomas and I live in Czech Republic in Central Europe. And of course sorry for my bad English.

I am contacting all of you for advice when I am finding a solution for my specific problem. I believe that there are skilled mechanics among you with many years of experience can help.

I recently bought an Indian Four motorcycle from 1932.
The bike is after a complete renovation, including the engine.
And just when the engine was running in, a fault appeared that I can't handle.
The third cylinder burns the mixture imperfectly, it works at about 30%, the spark plug is after disassembly wet and unburned.
The other cylinders work without problems.
I was able to rule out a fault on ignition, including another cables and spark plugs (I use NGK AB-6).
This indicates me a problem in the mechanical part.
The compression on all cylinders is about 4.6 atm (67.601 PSI). Valve clearances are: intake valve=0.15 mm (0.59 in), exhaust valve=0.25 mm (0.98 in).
The engine willingly starts and responds quickly to the accelerating of throttle.
That the cylinder does not work properly, despite the spark plug spark gives, I detected using a thermal camera (see attached, heat difference between 3rd (70.73°C=159.31 F) and 4th cylinder (127.15°C=260.87 F) .
I want to ask you for advice if someone would give me the answer where to look for a problem solving.
I've heard that third cylinders have always had a problem, but I can't believe it's been over 1 hour engine run-in.

Thank You for all your advices and responses.

 

Thank you very much. I will try.

 

Hey,

I probably solved the problem. After reading your advices and checking everything over and over, I came up with the following:
1. My original magneto had a weak magnets. This caused the spark to be weak and unable to ignite the mixture inside the cylinder.
Questions: How is it possible that three cylinders work and one does not. Why the spark from 3rd cylinder is always wet? The answer: Rich mixture.
2. That led me to the second problem. Carburetor.
The carburetor is not a complicated part. Unfortunately, during the general renovation, someone folded one of the needles (idle) incorrectly. Above the needle there should be a spring which allows to control the richness of the mixture. Someone put that goddamn spring on the needle from below. This ignorance caused the needle was open and a rich mixture to fly into the cylinders. Such a rich mixture could not be ignited at idle in cylinder no. 3 and in cylinder no. 4 there were insufficient explosions as well, although it was not heard. Now I will want to fine-tune it and I believe that we will only have pleasant moments with the new motorcycle for future.

Let me to thank you for your advices, contacts and support. The sun is coming. When I pull out my Indian from the garage, take a few photos and put them here.