Running-In Procedure


How much you need to nurse an engine during its running-in period will depend on how much work has been done on the engine. The most important case is when the engine has been re-bored and new pistons have been fitted. These are the components that will generate the most heat while being run-in and they are the most likely to result in engine seizure of mistreated. Other new components, such as re-ground journals, new bearing shells or bushes still need to be treated with respect but they are less likely to be seriously affected by over-enthusiastic riding for a short period.

However, the ease with which a new engine runs-in is dependent on the quality of the work that has been done and appropriate clearances being applied, particularly between the pistons, piston rings and bores. Inadequate clearances will result in the build-up of excessive heat, possible damage to the metal surfaces, tightening of the engine and, ultimately, seizure. If the engine is revving hard when a seizure occurs then connecting rods can break and significant collateral damage can result.

The good news is that none of this needs to happen if the rider is sensitive to the signs that the engine is showing and responds accordingly. If there is an increase in mechanical noise, excessive heat coming off the engine or a feeling of loss of power then stop immediately and investigate. If the engine is excessively hot, “squeeks” when it is turned over or feels stiff then there is a potential problem. Continuing to ride without giving the engine time to cool down and recover may lead to permanent damage. Temporary over-heating and slight stiffening isn't necessarily a cause for serious concern but a full seizure certainly is.

There is no fixed mileage at which a newly rebuilt engine can be said to be fully run-in but it is generally accepted that an engine can be pushed a little harder if it gets beyond 500 miles without showing any adverse signs and can be ridden normally once it has gone beyond 1,000 miles. These numbers should be treated with caution. The secret of successful running-in is to remain sensitive to what the engine is telling you throughout, even after you think that running-in process is complete.

Here is some basic guidance for the running-in period:

  1. Fill the engine with good quality mineral oil and keep the oil level topped up, checking it before every ride (oil consumption may be heavier than normal in the initial stages of running-in);

  2. In the first 100 miles or so, stop frequently to listen to the engine and feel the heat. If it doesn't seem right, turn it off and let it cool;

  3. While riding, listen for symptoms of excessive heat, such as increased engine noise and pinking under load or loss of power. Stop if you detect these signs and let it cool;

  4. Let the engine rev freely but don't rev it hard or let it sit at high revs for an extended period;

  5. Let the revs rise and fall through the lower ¾ of its range and avoid riding at the same revs for long periods;

  6. Don't let the engine labour. Too much throttle at low engine revs is damaging. If the engine feels like it is beginning to slog then change down a gear. If you are worried about sustained high revs in a low gear (on a long steep climb, for example) then stop once in a while and listen to the engine and feel its temperature, letting it cool if necessary;

  7. Change the oil after the first 500 miles and it is advisable to remove the sump to check for metal particles or fragments, if possible. Wash the gauze filter in paraffin or another oil-based solvent. Refill with good quality mineral oil. Don't use synthetic oils while running-in;

  8. If there are no adverse symptoms after a few hundred miles then you can push it a little harder and stop a bit less often but continue to be vigilant;

  9. After about 1,000 miles to 1,500 miles, change the oil again and adjust the valve clearances to the recommended settings;

  10. After that, resume a regular oil change and maintenance regime.