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Old 12-26-2010, 09:56 AM
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MarkSumpter MarkSumpter is offline
Motorized Bicycle Elite Member
Join Date: Nov 2010
Location: Ohio
Posts: 474
Default Re: Break in secrets

This is a very controversial topic !!
That in itself is one of the most telling statements of the article.

I have built small engines, Motorcycle engines, Car and racing engines alike and have used both methods of break in depending on the engine type and what it would be used for with varying degrees of success.

The biggest issues that causes engine failure especially during break in is improper dissipation of heat and improper clearances between working parts that cause them to either not seal properly if too great or seize if to tight.

This being said keep in mind that a high RPM break in will generate easily 30% more heat because of the increased RPM and unless you actually know that the Journal end play clearances are to spec and that you have measured the ring end gap to ascertain the rings have enough gap to not cause them to seize in the jug it probably is a better idea to stick with a "SOFT" break in.

Everything I have seen so far with the China engines has told me that they are really put together in a slap dash manner and little to no QC is given to them during assembly so I kind of doubt that the actually test fit rings for end gap let alone test the crankcases for seal integrity or check journal size for proper clearance.

I will say that "HARD" break ins when successful do tend to seat rings better and will add some longevity but you will also see a higher degree if initial failures especially in crate engines.

I think I will stick with a Soft break in for Chinas and allow the parts to wear into each other gradually.
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