Hi, after several tests and after having checked both the carburetion and the phase and the ignition, I believe that the detonations with the gas closed and that are accentuated when I go down a road, I think are due to the not perfect seal between the ucita of the exhaust gas of the cylinder and the silencer tube. in fact it vented in acceleration. both the tube that engages on the cylinder exhaust hole that the hole is not damaged. Has anyone found a remedy to have a good seal? I saw that the bikes are fitted with a collar at the exhaust outlet but on my m20 I would not like to mount it. tips? and then how can I believe that the detonations are due to what I have described? thank you
I had the same issue when I first drove my m20 - exhaust popping when deaccelerating (exhaust "detonation"), caused by a small air leak at the head exhaust port and header pipe. Not back firing out the carburetor, which may have other causes, but sounds similar. I purchased a tube of furnace cement, also known as stove gasket cement, at my local hardware store for a few dollars US. Claimed to withstand 2000 degrees Fahrenheit. Rutland is the brand name. Removed the header pipe - silencer (2 bolts), cleaned the head exhaust port and header pipe end, wet with a little water, applied a bead of cement inside the port and reinstalled the pipe and silencer. Waited 24 hours to dry completely, and ran the engine a few times to progressively warm the exhaust to operating temperature.
No more exhaust popping. 😁,
The cement gets brittle with use and age, making subsequent removal of the header pipe very easy. But lasts a long time in maintaining a high temperature seal.
Holt's make a product which is just like toothpaste. It's the same stuff that most exhaust places will use on every joint of you newly fitted car exhaust system and cures with the heat of the engine. Just a finger full smear round the pipe is all that is required. I use it on all my exhaust assembling ......'Belt and Braces' and as Dave said, it just breaks away on dis-assembly.
I had the same problem as well. Used the Holt's paste suggested by Ron, but the exhaust gas spit it out. I have had to disassemble the exhaust pipe, enlarge the side that enter in the cylinder to eliminate as much as possible the leak, and then the paste worked and is working.
