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lewis onions

An update on the current frustrating issues with this engine.

The barrels were re-bored to +0.080 and new pistons and rings fitted. When reassembled there was a noticeable escape of air from around the cranks when an airline was attached via the carburettor inlet so the engine was disassembled again and the cranks removed. This disclosed a number of problems: the crank had been put together with a woodruff key which was too long for the key-way which meant that the cranks were held apart; 0.098 of shims had been added; the glands were dished and so were not sealing in the cups; and the gland springs were both left-handed. Reground glands were blued and lapped in before reassembly with a shortened woodruff key, new left and right hand springs all with 0.012 end float.

The engine was refitted in the frame and ignition timed, checked and re-checked. The BTH Mag-generator was producing large fat blue sparks. The Binks carburettor has been rebuilt and the float level set as prescribed. So all was ready….

Or seemingly not. The engine stubbornly refuses to fire or run by kick stater or on rollers. The plugs quickly become warm and there is a faint smell of burning petrol but nothing more.

After many frustrating attempts using varying starting procedures – drenching the pistons with oil, liberally dousing everything in petroil, squirting neat petrol into the carburettor or down the spark plug holes there was still no sign of life whatsoever.

To make things worse, reverting to the Snap On compression tester the engine still only seems to be able to struggle up to 50 psi compression (at least we’ve doubled the original readings!) and observing the pistons on the up stroke through the transfer ports suggests that air is leaking back past the rings

Does anyone have any ideas before I push the thing into the canal and have done with it?