crank pulley wobbling - how do i fix this?
 

i'll post a video when i get home, but i'll try to describe this as best as i can.

when putting the pulley onto the crank, it wobbles back and forth. the hole on the pulley is slightly larger than the crank. the notch lines up, but there's too much play...

the piece on the pulley that has the hole...is that the boss? or hub boss?
can that be replaced without replacing the whole pulley?

thanks in advance. when i get home, i'll post a video for further clarification.

Buy a used pullie. There pretty cheep.

Did you have the crank machined? Was this the reason the pullie is off of the motor in the first place? Why, why is it too big?

this is a used pulley i got from a member here about 2 weeks ago.
it's out cause the engine is being rebuilt.

here's the video. it's a 99 engine

Which pulley? The front one with the 2 belts or the one that the timing belt goes on?

Just watched the video, have you tightened the main bolt down to 120ft/lbs and then installed the 4 10mm bolts on the big pulley?

crank pulley...the one with two pulleys. you can kind of see it in the video

this guy

https://www.miataturbo.net/attachmen...ine=1329274834

https://www.miataturbo.net/attachmen...ine=1329274834

https://www.miataturbo.net/attachmen...ine=1329274834

I think you need to tighten down the big bolt to 120ft/lbs and then see if it moves.

There's a plate that goes behind this pulley.

a) is it there?
b) is it oriented correctly? It has a front and a back. The center is slightly humped, the hump should go towards the front of the car, away from the engine.

Any chance of pictures of said plate?

https://www.miataturbo.net/attachmen...ine=1329274834

a) silver piece is the plate, no?

Plate was on later NA's and NB's for crank sensor. Looks like OP has one of the early ones since the TB cog has made an impression. I would tighten everything up and see if it runs true on the car.

I had a '00 engine with the #4 bearing fault. Mazda warranty replaced the engine and it never ran properly. Diagnosis eventually tracked the problem to a wobbling pulley (crank trigger miss) caused by A BENT CRANKSHAFT. Mazda replaced that engine too. Any chance you have a bent crank here?

doubt it...it's been measured and made sure that it's in spec during this build.

I have a pdf copy of the 99-00 service manual; here's a page showing the plate.

My engine is a bit different since it's a 2001, and my pulley looks different, no keyway in mine. However my page in the 2001 manual looks similar to this, so I'm assuming the plate is similar. My plate is ~1/8" thick, and has the same diameter as the accessory crank pulley. It is not attached to the pulley in any way, it is a separate piece which gets sandwiched underneath the accessory pulley. The inner area with the 4 bolt holes is the part that is humped.

https://www.miataturbo.net/attachmen...1&d=1329334915

that plate is there.
i took off the four bolts that bolt together the plate and the pulley boss from the pulley itself...the boss is shot (i think and hope). i just ordered a new one and it should be tight. i'll keep everyone posted, but i don't think i'll need to loctite anything. and i'm fairly certain the crank doesn't need to be replaced.
thanks for your help.

Scary. Try swapping the backing plate with another one - I doubt the crank wore down.

Take a picture of the keyway on the crank too.

i'll try to get a picture tomorrow, though i was just over there. the key is fine. the crank is fine.

I really doubt the crankshaft was bent.

The crank is pretty much the strongest thing in the whole miata.

Crank nose shouldn't be bent.
If the key way is fine to still be able to index the boss and crank together, it should be fine.

The assembly on yours from front to back should be..

21 mm bolt>>large accessory pulley>>boss pulley>>lower timing cog>>crankshaft.

(correct me if I am wrong)

You DID inspect the keyway inside the boss and on the nose of the crank correct?

yeah, crank is fine.
keyway is fine.
hoping it's the pulley boss.

when we unbolted the four bolts that hold the pulley to the boss, flipped the boss over and there was considerably less play on the nose of the crank. obviously you can't bolt it on like that and expect it to work. we just did this to test the theory that the boss was not to spec...and it was not.