Topic: What qualifies an engine as having been rebuilt?

[dylboss]

Can anyone tell me what constitutes an engine as having been rebuilt?  I know the obvious, such as piston and rings, cams, valves, but what other internal parts would need to be replaced in order to classify it as a rebuilt engine?

Thanks.

[MCRider]

Can anyone tell me what constitutes an engine as having been rebuilt?  I know the obvious, such as piston and rings, cams, valves, but what other internal parts would need to be replaced in order to classify it as a rebuilt engine?

Thanks.

Good question. I think there is no such thing. The term can only be used with qualifiers, an explanation of whats been done.

A "rebuild" to me would imply fresh main bearings for example. But why would you replace them if they are still in spec? So its actually an inspection, replacing parts as needed.

Or in your example you include cams and valves. But why would you replace these if they are still in spec? And if you leave them alone, is it still a rebuild?

A partial rebuild would have no limits to its variety.

A complete rebuild would be replacing parts for no good reason. If you disassembled it for a complete rebuild, find the primary chains to be 40% gone, do you replace them? And if not, is it still a rebuild? Has the practical life of the engime really been reached? Will it actually ever be reached in that owner's lifetime, as we are riding it less and less.

You could have a "complete inspection" replacing parts out of spec. But even that implies some judgement calls.

Or it had a "top end inspection" rings replaced, valves lapped in, (or whatever) all new rubber (seals, etc.) Its got to be spelled out. "Rebuilt" by itself is meaningless.
In my mind.

[Shoeboxjoe]

Yea I think vague terms like that get tossed around too easily. I'd be weary of most "rebuilt" engines unless i knew the guy or the shop where the work was done. Also if it was done at a shop i'd look at the receipt or statement of work.

I'd define "rebuilt" as having all new seals and gaskets along with a complete inspection of all internal components and replacement of everything found to be out of factory spec.

[MCRider]

Yea I think vague terms like that get tossed around too easily. I'd be weary of most "rebuilt" engines unless i knew the guy or the shop where the work was done. Also if it was done at a shop i'd look at the receipt or statement of work.

I'd define "rebuilt" as having all new seals and gaskets along with a complete inspection of all internal components and replacement of everything found to be out of factory spec.

I agree in principle, but have you ever seen what the factory considers "out of spec" for piston ring end gaps for example. Going by that you'd never (hardly ever) replace anything.

[dylboss]

MCRider, you bring up some very interesting points.  I'm not interested in buying a rebuilt engine, but I do plan to rebuild my CB550 at some point. I guess I want make sure I'm covering all my basis with a "rebuild", and make sure I'm doing due diligence by calling it a rebuild.  Also, plan to change the odometer at that time, and want to make sure that is kosher with a true rebuild. 

Seemly there must be some set of criteria for calling something a rebuild.

[MCRider]

MCRider, you bring up some very interesting points.  I'm not interested in buying a rebuilt engine, but I do plan to rebuild my CB550 at some point. I guess I want make sure I'm covering all my basis with a "rebuild", and make sure I'm doing due diligence by calling it a rebuild.  Also, plan to change the odometer at that time, and want to make sure that is kosher with a true rebuild. 

Seemly there must be some set of criteria for calling something a rebuild.

Last first:
I think you define the term. Frankly, I'd stay away from it. I'd say "inspect and replace as necessary". There is no beginning or end to "rebuild".

Changing the odo may have legal implications. Older bikes, maybe not. But you'd have to "inspect and replace" on the chassis as well.

[Jerry Rxman Griffin aka MuthaF'er]

Rebuild to me would mean total tear down and inspection of all parts with replacement of any part not within specs or with obvious problems. All gaskets and seals would be replaced in doing so. 

[KingCustomCycles.com]

For what it is worth, the FAA has defined rebuilt vs. overhauled and is very specific when it comes to aircraft piston engines.  Overhauled is disassembled, cleaned, inspected, repaired as necessary, and tested in an acceptable manner.  Rebuilt is disassembled, cleaned, inspected, repaired as necessary with all parts complying to new part tolerances.  Not new parts, just parts that are within the manufacturers limits.  Aircraft have serviceable limits and manufacturers limits with the serviceable obviously being looser than the manufacturers.  I would say a motorcycle engine that has been disassembled completely, cleaned, inspected, repaired as necessary and reassembled with new gaskets, seals, would count as what most people call rebuilt.  Everything else is just a repair.  I would never remove the cylinder without deglazing and replacing the piston rings but I consider that a repair and would not call it rebuilt. 

[OldSchool_IsCool]

So where does the term "Refreshed Top End" come in?

>>runs for cover<< 

[KingCustomCycles.com]

STOH, Since Top Overhaul, This is the overhaul of the "top end" not normally including anything inside the crankcase or accessory case.  I would venture to say that most SOHC engines described as rebuilt have simply had the top end refreshed as the low end is fairly bullet proof.