I'm starting to think the tech just don't know what he's talking about. He told me "12". When he said that I asked 12 thousandths? And he said yes, but with a slightly confused look. So I really think he saw .0012 on the indicator and doesn't know how to read the thing and just told me 12.
If the runout is 0.012”, it is beyond the maximum published service wear limit and corrective action shouldn’t be a hassle; if it is 0.0012” you have straight set of flywheels. You can easily see 0.012” of runout with the naked eye at the bushing end of the shaft as the crank is rotated with the camplate assembly removed.
There are a couple of things going on with regard to the crank runout specifications. The service manual has three specifications in two categories. Two of the three specifications are measured with the crankshaft supported between centers in a truing stand or similar equipment. There is runout measured at the flywheel rim and runout measured at the shaft’s main bearing area next to the flywheel. The third Specification is with the crankshaft supported by its main bearings, with the runout measured at the outboard end of either shaft; usually the gearshaft bushing end.
The two categories covered in the specification are manufacturing tolerances and service wear limits. I believe that these specifications are the same all the way back through the Shovelheads and possibly earlier.
The current specs are:
Manufacturing Tolerance (new)
Runout at Rim = 0.010”
Runout (shaft at flywheel) = 0.002”
Crankshaft Runout (bushing end) = 0.003”
Service Wear limits (used)
Runout at Rim = 0.015”
Runout (shaft at flywheel) = 0.003”
Crankshaft Runout (bushing end) = 0.010”
As illustrated in the specifications, the values realized in the truing stand are a fraction of the values realized when assembled and measured at the bushing end of the gearshaft. It is my experience with the bolt together cranks that values of approximately 0.0008” to 0.001” in a stand measured next to the flywheel will return gearshaft runout values of an installed crank at the bushing end very close to 0.002”. It is also my experience that for the most part, Twin Cam gearshaft runout at the bushing end regularly falls under 0.002”. IMHO, this is a very straight set of flywheels by any standard, especially when compared to the EVO’s. In an EVO with any mileage, I would consider gearshaft bushing end runout under 0.002” to be remarkable.
djkak
Author
Topic: Checking the runout? (Read 5433 times)