22-06-2018, 11:08 PM
Nothing feels bad when I turn the engine over on the handle.
I built the engine some years ago with a re-bore, new pistons, new valves etc and it hasn't done that much mileage since. I'm an engineer and was very careful to assemble the engine properly.
The oil is clean, there's no evidence of the water in the radiator being pressurized by a gasket failure and with the plug out there didn't seem to be anything ejected when it was running. In fact I had expected it to be a little more dramatic but it wasn't, the engine just ran slightly better on three cylinders than with the plug in. It doesn't seem to be a mis-fire as such, it appears that this cylinder just doesn't fire at all either at tick-over or if the engine is revved.
I feel that either one of the valves is either burned or not seating properly (although I've no idea why this would have happened) or despite there being a good spark at the plug when it's out of the engine something is breaking down when it's actually under load. As I write I must say that also seems unlikely. There must be fuel because the next cylinder which breaths through the same part of the inlet manifold is working OK, and this also really eliminates both ignition and cam timing.
Although I'm reluctant to start taking the engine apart when I don't know what's wrong I suppose this is the next logical step.
John.
I built the engine some years ago with a re-bore, new pistons, new valves etc and it hasn't done that much mileage since. I'm an engineer and was very careful to assemble the engine properly.
The oil is clean, there's no evidence of the water in the radiator being pressurized by a gasket failure and with the plug out there didn't seem to be anything ejected when it was running. In fact I had expected it to be a little more dramatic but it wasn't, the engine just ran slightly better on three cylinders than with the plug in. It doesn't seem to be a mis-fire as such, it appears that this cylinder just doesn't fire at all either at tick-over or if the engine is revved.
I feel that either one of the valves is either burned or not seating properly (although I've no idea why this would have happened) or despite there being a good spark at the plug when it's out of the engine something is breaking down when it's actually under load. As I write I must say that also seems unlikely. There must be fuel because the next cylinder which breaths through the same part of the inlet manifold is working OK, and this also really eliminates both ignition and cam timing.
Although I'm reluctant to start taking the engine apart when I don't know what's wrong I suppose this is the next logical step.
John.