Well, the engineers down at Perth got back to us yesterday with some good news, and some not so good news……The cause of the rough running engine is a surprising one.

The good news is that it wasn’t the engine, itself, or the plugs. The bad news is that the exhaust pipe coming out of the manifolds, at the joint where it goes into the muffler, has completely sheered! This left the engine with effectively continuous Carb’ heat and fouled the plugs in the process. This, combined with the detached exhaust, explains the vibration experienced, as well as the power drop.

Applying the carb heat compounded the effect, which resulted in the larger power drop I experienced. See the picture below – it’s not very clear, but if you look closely you can see a 5mm or so, circumferential space where the down-pipe should connect to the muffler and exhaust residue on the hosing leading off to the carb heat. How and why this weld joint should suddenly fail, is anyone’s guess – it was an old section of exhaust, so I suppose over time it has cracked and weakened and then failed completely. So we’re looking at a new section of exhaust and a weld repair – hopefully the muffler itself will be fine. At least it’s not cracked cylinders or something as equally expensive.

The whole bottom part of the exhaust ( the new heat exchanger / exhaust box etc ) is hanging on by just the hose! I never would have thought of this being at the cause of the trouble – every day is a school day, as they say, and our loveable old Auster continues to try us!