Plated Cylinders

Pros

Cheaper to manufacture (initially)

Lighter by about 150gm (125cc cylinder).

The plated surface is very hard and suffers almost no wear.

However the aluminium behind it is soft and “packs back” over time, resulting in an increased piston clearance, even without bore wear. This cannot properly be rectified with a larger grade of piston since the wear is not uniform and a larger grade piston will be at risk of seizure.

Can potentially run very small piston to bore clearance to give a performance advantage.

Very few engine builders, or indeed manufacturers are prepared to run so close to the edge for their customers. Almost all choose to run clearances in the order of 0.040mm, exactly the same as a linered cylinder! – Forged pistons often need even larger clearances!!

Actually a linered cylinder bore will expand by the same amount as an unlinered (nikasil) cylinder. The reason for this is that the sleeve is fitted under the compression of an interference fit. Although the aluminium when heated, expands at a greater rate than the iron, the iron is expanding the the same rate as the aluminium, because the compression from the interference fit is reduced This reduction in compression allows the iron sleeve to expand at the same rate as the aluminium !

Even if only the aluminium cylinder was heated and the sleeve was cooled, the sleeve would still expand because of the relaxation of the compression exerted by the aluminium cylinder !

This is why linered cylinders can run with the same clearance as plated cylinders.

If the liners are cast into the block (without the interference and compression), this does not apply and such cylinders will indeed need more clearance (in theory).

Cons

Expensive and very time consuming to re-condition – cannot be rebored.

Cannot easily be honed to remove small imperfections or damage so that even the smallest fault cannot safely be rectified.

Running an imperfect cylinder risks plating detachment and total failure with potential catastrophic collateral damage to the rest of the engine.

Linered cylinders.

Pros

Mitaka offer an economical relining service.

The initial wear can be easily corrected by honing and a larger grade piston fitted to restore the exact specification.

Extended wear or serious damage can be economically repaired by reboring.

Cons

Heavier (150gm)

Can’t think of anything else, unless you can afford a new cylinder for every race.

WHICH IS THE BEST SOLUTION FOR YOU ?