Checking condition of crankshaft

[xwhatsit]

I've got spare three crankshafts sitting around. One has massive big-end play, one is still inside an engine; however the third one I have out of the engine and it seems maybe OK.

My Haynes manual says to grab the conrod and firmly push/pull it. There is a small amount of radial play (supposedly normal), but I'm 99% sure I can't detect any longitudinal play in it, with my `naked hands'. Is that good enough? Any other tips on making sure of big-end condition?

The small-end is another story. Haynes says the gudgeon pin should be a light sliding fit -- but definitely no radial play. It also says radial play should be very unlikely. With an old gudgeon pin (from a rather mangled piston), it slides, until it gets halfway, then there's a sort of seam on the pin that makes it difficult to go further. There does seem a small amount of radial play, difficult to notice. There's no bush. What's the normal approach in this case?

[Patch]

What's the normal approach in this case?

Give it to an experienced engine builder who knows what the fuck they are doing

[tri boy]

No good checking for sm end play with a worn pin.
A dial gauge may help in identifying big end brg wear, but on a built up crank, I would be happy with smooth rotation of the rod and not feeling any wear, side clearance to the crank web/big end is about .15mm I think, by memory.
Also getting the rod checked to see if it's not bent, and a set of V blocks and dial gauges to check for crank run out helps.

Signing onto a polytech night class on engineering practice, opens a world of tools n skills to those who like to tinker. Imagine having access to a million dollars worth of tooling, and grumpy old blokes to show you how to operate lathes, mills etc....
Many project bikes have been built using polytechs.

[xwhatsit]

Give it to an experienced engine builder who knows what the fuck they are doing

Now where would the fun be in that?

No good checking for sm end play with a worn pin.
A dial gauge may help in identifying big end brg wear, but on a built up crank, I would be happy with smooth rotation of the rod and not feeling any wear, side clearance to the crank web/big end is about .15mm I think, by memory.
Also getting the rod checked to see if it's not bent, and a set of V blocks and dial gauges to check for crank run out helps.

Signing onto a polytech night class on engineering practice, opens a world of tools n skills to those who like to tinker. Imagine having access to a million dollars worth of tooling, and grumpy old blokes to show you how to operate lathes, mills etc....
Many project bikes have been built using polytechs.

Cheers man -- I suspected using an old pin might not be much help, but that's what the Haynes book of lies said

Polytech sounds like fun, but I have enough grumpy lecturers on my plate right now as it is.

Thanks!

EDIT: One more thing, Honda never sold separate bits. If the rod or bearings were fecked, you had to buy a whole new crank assembly. However I've seen conrods on Japanese sites; it's therefore possible to pull it apart? Maybe put new bearings in? Might be cheaper than a new crank if it needs doing.

[Ixion]

With a built up crank, condition checking is really a matter of feel and experience.

Wash the big end out with petrol. Hold the crank in a vice (so it doesn't move at all, in your hands it will). Now hold the rod vertically and move it up and down . Repeat at 90 180 and 270 degrees. Do this in a very quiet environment and listen hard. You'll hear and feel even a very slight movement. Turn the rod listening for any 'bad' noises.

Put the crank pin at bottom dead centre , so the rod is coming up between the flywheel faces. There will be a small amount of sideways rock at the small end. We are looking for "rock" here, NOT sideways movement. There will always be some. I use a rough rule of thumb that less than half the distance between the rod and the flywheel web is OK. The manual may specify a figure.

Some cranks have thrust washers on the big end . Check for sideways movement (not rock). There should always be a bit, a few thou. The manual may have figures.

Look for scoring on the shafts, ovality of the little end (put a good condition gudgeon pin in and try to rock it, there should be none).

If all that looks OK, I'd use it, unless it was a racer or something.