sediment in cylinder and on piston head?

[mountainman_oef]

OK so I keep blowing through exhaust haskets and i figured this weekend I would do a few things. Port the exhaust and intake, reduce the baffle, rebuild carb and figure out why my clutch isn't catching. Well my carb turned out to be the leaky culprit with the clutch and all my pads are soaked in gas, hence the slipping. but when i took the head off i noticed quite a bit of sediment on the top of the head and piston. the top of the head is more of a hard black film and the piston is gunky and guey.



so does anyone know what caused this? gas ratio? I have a feeling I have way to much back pressure but would that make this happen?

 

[Deleted member 12676]

probably a combo of crappy brand oil at too rich a fuel mixture.
back pressure has nothing to do with it.
try semi-synthetic oil at 30:1 and lean out your fuel mixture.

 

[Bzura]

That black paint that I see peeling from the dome is probably contributing to what's gunked up on top of the piston. A wire wheel on a dremel will take card of the rest of what's on there & then plane down the head with sandpaper on glass afterwards to make sure it's a nice flat surface.

 

[Fabian]

OK so I keep blowing through exhaust gaskets

If you are blowing exhaust gaskets, try and take a good quality file and very carefully file the face of the muffler exhaust flange so it's surface is perfectly flat and true, then use a conventional gasket and cover it with Permatex Ultra Copper; on both sides:






Once the muffler is bolted in place, you will not have any more issues blowing exhaust gaskets.

If you are blowing the aluminium cylinder head gasket, then my advice (for more than one reason) is to order a CR Machine Manufacturing medium compression cylinder head.
You will """NEVER""" have any more issues with either blown cylinder head gaskets or leaking cylinder head gaskets.

when i took the head off i noticed quite a bit of sediment on the top of the head and piston. the top of the head is more of a hard black film and the piston is gunky and guey. I have a feeling I have way to much back pressure but would that make this happen?

Don't even place any concern over the carbon deposits on the inside of the combustion chamber and the piston. It won't have any negative influence on engine life or engine performance if 25:1 oil/fuel ratio is used, with the engine having a reasonable amount of load and showing reasonable exhaust gas temperature.

If the engine is only lightly loaded; being asked to only putt-putt around at low throttle, then you can lean out the oil/fuel ratio without any negative effect on engine life.

 

[mountainman_oef]

Awesome stuff. thanks guys