Gypo Logger
Timber Baron
The object of running in an engine, is to get the engine to the point where all the rubbing surfaces are perfectly mated to each other at all temperatures likely to be attained, while causing as little wear to the engine as possible in the process. The benefits of doing this properly are twofold; the engine would be a 'better' engine throughout it's life, and that life would also be extended.
The method used to achieve this is simple. Run the engine very rich and lightly loaded at first and gradually increase the amount of work the engine is allowed to do, at the same time gradually increasing the temperature that the engine is allowed to attain, by judicious use of the main needle valve. This gradual process is spread over approximately the first half hour of the engine's life when it should be ready for its first full speed run. During all running of new engines, the setting should be on the rich side of peak power.
Run the first tankful absolutely soggy-rich. Keep all runs of short duration of one-half to one minute, with a few minutes cooling down time between each. The number of heat cycles makes the metal "set" and speeds up the final fit of the components. The rich mixture and the short runs prevent the temperature from rising too much. Debris that forms will be washed away by the excess fuel and oil.
For the next few runs set the main fuel needle to give a very fast four-stroke with just the occasional hint of two-stroking. Allow engine to run for 30 seconds and then stop for a two minute cooling period, Start again for 30 seconds then allow to cool again. Gradually increase the length of the full throttle runs, unless the engine shows a tendency to bind, which can be heard by the labouring sound and unwillingness to maintain a steady rpm. At the end of two tankfuls lean the engine out to the point where the engine is on the verge of two-stroking and four-stroking and go fly, reducing throttle from time to time to allow the engine to cool a bit. Keep this up for about four litres of fuel. By now the engine should be steady running, without any tendency to sag, and can be leaned further to the point, that max. power is achieved. Always back off the needle a bit until a clear drop in rev's can be noticed.
If the engine is to be used under more harsh conditions (e.g. with a tuned pipe or high nitro fuel), then it will need some extra running-in under the short-run procedure, using the same fuel as for it's intended use, but with extra oil added. 25% oil is not too much for the first runs of a racing engine and will do it a lot of good.
All this might seem a long-winded process but it is necessary to get the best surface finish with the least wear inside your precious engine.
The reason for everything being done in small and gradual steps is that the rubbing surfaces have to be mated at gradually increasing pressures and to further complicate this the shape of the parts change as temperatures are increased. As an illustration, the cylinder and piston are round and parallel sided when made. As the engine warms up the top half of the cylinder gets hotter than the bottom half and so expands unevenly. That is the reason, that a well run-in engine has a bit less compression during starting than a new engine.
The piston and ring are subject to similar stresses. The ring alters its length depending on temperature and is also going up and down a bore which is no longer round or parallel sided and is guided through this operation by a piston which gets hotter at its head where it is in contact with the burning fuel mixture and therefore the diameter of the head is bigger than the walls. The exhaust side of the piston is hotter than the transfer side so the piston is no longer round or, as mentioned earlier, parallel sided either. All these distortions are larger or smaller depending on the temperature of the engine, so the running-in process has to allow the engine to make the mating working surfaces suitable for all these varying conditions.
During the run-in check all screws and bolts for security and if you have to tighten any cylinder head bolts, remember to tighten a little at a time and in diagonal rotation. You might also find the sparkplug has been affected by small metal particles fired at it during running-in. If you have any doubts change it and keep the old one only for running-in only, or throw it away. It did serve it's duty.
Original publication by Norman Osborne
Adapted to current views by Pé Reivers
John
The method used to achieve this is simple. Run the engine very rich and lightly loaded at first and gradually increase the amount of work the engine is allowed to do, at the same time gradually increasing the temperature that the engine is allowed to attain, by judicious use of the main needle valve. This gradual process is spread over approximately the first half hour of the engine's life when it should be ready for its first full speed run. During all running of new engines, the setting should be on the rich side of peak power.
Run the first tankful absolutely soggy-rich. Keep all runs of short duration of one-half to one minute, with a few minutes cooling down time between each. The number of heat cycles makes the metal "set" and speeds up the final fit of the components. The rich mixture and the short runs prevent the temperature from rising too much. Debris that forms will be washed away by the excess fuel and oil.
For the next few runs set the main fuel needle to give a very fast four-stroke with just the occasional hint of two-stroking. Allow engine to run for 30 seconds and then stop for a two minute cooling period, Start again for 30 seconds then allow to cool again. Gradually increase the length of the full throttle runs, unless the engine shows a tendency to bind, which can be heard by the labouring sound and unwillingness to maintain a steady rpm. At the end of two tankfuls lean the engine out to the point where the engine is on the verge of two-stroking and four-stroking and go fly, reducing throttle from time to time to allow the engine to cool a bit. Keep this up for about four litres of fuel. By now the engine should be steady running, without any tendency to sag, and can be leaned further to the point, that max. power is achieved. Always back off the needle a bit until a clear drop in rev's can be noticed.
If the engine is to be used under more harsh conditions (e.g. with a tuned pipe or high nitro fuel), then it will need some extra running-in under the short-run procedure, using the same fuel as for it's intended use, but with extra oil added. 25% oil is not too much for the first runs of a racing engine and will do it a lot of good.
All this might seem a long-winded process but it is necessary to get the best surface finish with the least wear inside your precious engine.
The reason for everything being done in small and gradual steps is that the rubbing surfaces have to be mated at gradually increasing pressures and to further complicate this the shape of the parts change as temperatures are increased. As an illustration, the cylinder and piston are round and parallel sided when made. As the engine warms up the top half of the cylinder gets hotter than the bottom half and so expands unevenly. That is the reason, that a well run-in engine has a bit less compression during starting than a new engine.
The piston and ring are subject to similar stresses. The ring alters its length depending on temperature and is also going up and down a bore which is no longer round or parallel sided and is guided through this operation by a piston which gets hotter at its head where it is in contact with the burning fuel mixture and therefore the diameter of the head is bigger than the walls. The exhaust side of the piston is hotter than the transfer side so the piston is no longer round or, as mentioned earlier, parallel sided either. All these distortions are larger or smaller depending on the temperature of the engine, so the running-in process has to allow the engine to make the mating working surfaces suitable for all these varying conditions.
During the run-in check all screws and bolts for security and if you have to tighten any cylinder head bolts, remember to tighten a little at a time and in diagonal rotation. You might also find the sparkplug has been affected by small metal particles fired at it during running-in. If you have any doubts change it and keep the old one only for running-in only, or throw it away. It did serve it's duty.
Original publication by Norman Osborne
Adapted to current views by Pé Reivers
John
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