Please forgive my newb question, but I've seen many posts about gear driven cams that say "if the runout is good". How does one check runout?

 

Go over to you tube and there should be several videos showing how to do it. It would be better than me trying to explain.

 

With a dial indicator. Generally if runout is .003 or better you can get away with gear driven cams

 

So there's no way to know ahead of time if you shoud order gear drive or chain?

 

I'm replacing my cams with another chain driven cam. Other cam change writeups suggest to check the runout, but why? Am I looking for a number that should concern me? My bike is a 2012 with 5k miles. I'm not sure if I should spend the money to buy a dial to measure this when I'm not sure what I would do with the information I get...and what exactly is it measuring???

 

That is right about gear drive, as it is gears that will not work with too much runout. Chain drive cams are fine, so you can order them in advance, if you decide to use them.

 

You are checking to see if your crank is straight like an arrow shaft or like a bananna. Straight being .003 or less movement. If your crank has to much movement the gears of the cams will walk, move, grind, make noise and destroy themselves

 

Actually it's checking concentricity.

 

Ok so if I'm going to change cams to another chain driven cam, does the same tolerance (.003) apply? If not, at what value should I be concerned? Or do I need to check it at all considering my bike is fairly new? Thanks.

 

Chain driven cams can run fine if your crank is within harley spec, an outlandish .012, its hard to imagine any bike being able to run for long with greater than that.

If you want chain driven cams I wouldnt bother with checking runout.

But why are you fixated on gear driven cams? I'd bet that the overwhelming majority of cam upgrades are chain.

Some people are very concerned about this spec, with some justification for sure. But improving crank runout requires splitting the cases and doing expensive work upwards of $2K. And then you still have to buy and install your cams.