31-05-14, 08:55 AM
That stuff does look like swarf from drilling. Any idea what it is, i.e. is it magnetic? Is more of it near one particular carb inlet?
It's not impossible for debris to make its way "backwards". I had a CG125 that became an absolute bastard to start… on investigating I found the choke flap had broken off the butterfly, the flap itself was in the air box and the steel pivot rod was in the exhaust pipe (the piston and cylinder head had a lot of dings, but the valves and seats had survived somehow).
Do your carbs look OK inside?
If it is from the engine itself it must have been running like a bag of spanners. I doubt if it's possible for the timing chain to slip enough teeth for valves to collide with the piston yet the engine still be capable of running. Perhaps a failed inlet valve spring could do it… would work ok at low revs, but wouldn't close quick enough further up the rev range causing collisions with the piston and blowing the debris back up the intake. All a bit hypothetical really, let us know what you find!
It's not impossible for debris to make its way "backwards". I had a CG125 that became an absolute bastard to start… on investigating I found the choke flap had broken off the butterfly, the flap itself was in the air box and the steel pivot rod was in the exhaust pipe (the piston and cylinder head had a lot of dings, but the valves and seats had survived somehow).
Do your carbs look OK inside?
If it is from the engine itself it must have been running like a bag of spanners. I doubt if it's possible for the timing chain to slip enough teeth for valves to collide with the piston yet the engine still be capable of running. Perhaps a failed inlet valve spring could do it… would work ok at low revs, but wouldn't close quick enough further up the rev range causing collisions with the piston and blowing the debris back up the intake. All a bit hypothetical really, let us know what you find!