Engine Rebuild & Detailing

There was a sure leap of faith or plain naivety when deciding to operate on the SR250's heart.

The engine was disassembled in order for a proper detailing treatment and to paint the engine black. By opening the engine I was taking a risk because any damaged parts are difficult to come by. But it was also the only way to avoid the tackiness of bolts and washers cast under what would look like dried chocolate sauce. So the whole lot was pulled apart to achieve a clean finish.

Whilst all it's bits were exposed, when better to clean the gunk out and get as close as possible to a brand new engine. First the old oil was drained out and flushed with new oil and filtered by a new oil filter. I ran this process a few times to thoroughly filter out the burnt bits and metal shavings floating around inside.



Working from the bottom up, the top end and side cases were disassembled and cleaned. All the factory clear coat (that had started to yellow) was sanded back and polished. The rocker caps received the same treatment.

After unbolting the top end, the engine ports were sanded and cleaned out. The cylinder had some slight burn marks like the back of an old fry pan. That was sanded back and wire-brushed to a shiny piston.

Next came the paint treatment and detailing of the cooling fins. The fins were flattened out and cut with a grinder, then sanded for a smooth and shiny contrast to the gloss black engine paint, heat proof stuff of course.

Before reassembly, all the gaskets and o-rings were replaced. Since gaskets are made from a compacted fiber material they get worn down over the years just like cardboard soaking in puddle of water. The new gaskets were essential for reliable air tight seals.

Oil has been cleaned out. The engine ports have been cleaned out. The piston itself has been had it's burn marks cleaned.

Finally, the engine was reassembled by my trusty mechanic who torqued the bolts tight and adjusted the valve clearances.