Rebuilding our Matchless: Run in a new engine – Part 4

In our final chapter of the G3L rebuild, we look at how to treat a freshly rebuilt engine without the risk of having to fix it all again!

Words, hassle and impatience by Matt
Wisdom and patience by Hutch
Tea and wheel-building skills by Shelley

Matchbox genie
After much more time, effort and money than we thought, our G3L rolls on its wheels; if slowly. From an oil leak from the pushrod tubes to a complete top-end rebuild, the 350cc single just needed the carb cleaned, checked and put back on, starting first kick!

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Hutch let the engine tick over getting to operating temperature, checking the oil was returning to the tank with a torch, while listening for unwanted noises and unwanted leaks.

He then let it cool down overnight and checked the tightness of the nuts and bolts of the parts we had disturbed – the barrel, head and rocker cover.

Oil? Check. Nuts and bolts tight? Check. Fuel? Check. Feel the kickstart movement – does it feel right?

Our bike has got a new piston and rings, though the barrel didn’t receive a full rebore as it was so worn, it was close to the next over bore size, so we honed it to the correct tolerance for the new slug and rings.

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Hutch honed it a fraction more to give a good clearance before fitting, but the finish is still different to a completely rebored barrel, so running in will be a little easier on ours.

Crucially, look in the oil tank to check that the oil is returning

Most rebuilds will receive a new tank of fresh oil, but ours had only been changed 14 miles before with good quality 20-50 so, as we will be changing it again soon, we left that in.

How should you run a rebuilt engine in?

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Many different opinions exist on the best way to run an engine in; however this is ours.

Kickstarting will feel different as the engine begins to coke up and bed in

Mechanical sympathy is the key – listening, checking and taking into consideration what the different parts are doing.

Read more and view more images in the June 2019 issue of CBG – on sale now!

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