Mankdrake 2661

iTrader: (8)

I replaced both rotor bearings in my rebuild. The clearance for the bearing to the e-shaft is very tight. It won't spin by hand. Is there a more than one bearing for 2nd gen motors? I got the bearings straight from mazda. Is this normal for new bearings?

farberio

iTrader: (7)

Check the clearance vs FSM.

Mankdrake 2661

iTrader: (8)

So, let's say the clearance is a tight .001. FSM says .0016-.0031.
It's not in spec. What can be done?

djchiptoothsfc

iTrader: (2)

Your assed out.

bumpstart

flap disk to clearance, may have to go through the top babbitt layer

NoPistons!

iTrader: (3)

Machine shop, son.

You can either turn the bearings or micro-polish the e-shaft to get things in spec.


I dunno if a flap disk is accurate enough to justify over spending a small fee at the machine shop GIVING them your specific tolerance to the hundredth thousandth of an inch.

Turblown

iTrader: (12)

When you say " It " won't spin by hand, is this with the engine assembled? Will it spin by hand before you torque down the tension bolts? Will it spin by hand with one of the stat gears out? How did you measure the bearing clearance?

RotaryEvolution

iTrader: (30)

never seen it, are you sure you aligned up the lock on the bearing? if not then it got munched when you pressed it into the bore. also be sure to clean any old materials off before installing the new bearings.

David Dale

lol ironically this same thing just happened to me...the new bearings in the rear stationary gear are too tight around the e-shaft. It looks like the tab is lined up and its pushed in the right amount...then again i wasn't allowed to sit and watch the guy press them in...so idk if he cleaned the surface good :/. Should i go get it pressed out again to make sure its put in right? (and can i re-use my new bearing)

Oh...and is the motor supposed to spin easily once both stationary gears are in place or will it be kinda hard?

lastphaseofthis

iTrader: (8)

were the housings possibly over heated? the only engine i had that wouldnt turn over by hand had housing warpage. the rotors were actually wider then the housings, and i would suspect them first. also remove the stat gears are revvin said, to eliminate them from the equation. even .0001 tolerance bearings shouldn't hold the shaft.

David Dale

i was just curious whether or not its supposed to be easy to turn it or require a little more effort because your not supposed to spin the engine until you install the rear stationary gear right?

and i actually have 2 eccentric shafts...the stationary gear won't spin freely around either of the two (or rather the e-shaft won't spin freely)...one of them being the e-shaft i had in the engine before... the front stationary gear is perfectly fine though. so i know there's something odd with the bearing...

SoloII///M

iTrader: (13)

I would be concerned that the bearing was not pressed in correctly or that the journal in the rotor is damaged. If the bearing is not pressed in squarely it can be deformed. You need a very beefy, very stiff press and the proper tool to press in rotor bearings properly. I would never do it on my shitty 12-ton HF press because it is just not stiff enough. It sounds to me like they were damaged during installation. There is only one size of bearing. It's not like a piston engine where you can get bearings that are a few thou under to allow for crank machining.

Use a bore gauge and micrometer to measure several points inside the bearing. Measure the e-shaft at several points. Calculate the clearances.

The engine should spin freely so long as both stat gears are installed and the journals are well lubed with assembly oil. Doesn't matter if the tension bolts are tight or not.

I second the recommendation to check the warpage of the irons and housings as well as the width of the rotors relative to the housings. These are all things that you should have documented any time you build a motor so I'm sorry if I'm stating something you already did, I just don't want to understress the importance.

JV

David Dale

Thank you very much for your help and knowledge, i will go remeasure everything

David

scathcart

This is exactly why you never replace the bearings in these cars. I am yet to see one that needing replacing unless the engine oil was severely contaminated, or there was an oil supply problem. Even in that case, best bet is to just replace the component instead of the bearing.
The whole "copper showing = bad" thing on bearings is a complete myth.

SoloII///M

iTrader: (13)

Never replace bearings? I can't say that I agree with that. The bearings that came out of my 175,000 mile motor were over the limit for clearance versus the crank journal, whereas a set of new ones is spot on.

Properly installed, new bearings are fine. The key here is "properly installed."

scathcart

I've taken apart engines with more miles that still spec'd within the limits. Even with new bearings, break-in is longer due to having to heat cycle the new bearings, and installing new bearings properly is very difficult. Hydraulic press is never rigid enough; an arbour press is required.
If the bearings are by some wonder out of spec, I just replace the parts with good, seasoned parts.

SoloII///M

iTrader: (13)

I guess we'll have to agree to disagree on this one.