I'm in the process of rebuilding my 13B and I'm about to order the bearings (main and rotor are (just) within specs, but the copper shines through).

But how do I know, which size of them to buy?

At RHD Japan, there are for example these sizes for the main bearings:
Part Num. : NF01-10-E040 (Yellow 1.980mm)
Part Num. : NF01-10-E050 (Green 1.983mm)
Part Num. : NF01-10-E060 (Brown 1.986mm)
Part Num. : NF01-10-E070 (Black 1.989mm)
Part Num. : NF01-10-E080 (Blue 1.992mm)
Part Num. : NF01-10-E220 (Yellow 1.988mm)
Part Num. : NF01-10-E230 (Green 1.991mm)
Part Num. : NF01-10-E240 (Brown 1.994mm)
Part Num. : NF01-10-E250 (Black 1.997mm)
Part Num. : NF01-10-E260 (Blue 2.000mm)
(RHDJapan : Mazda OEM Main Bearing Set Stationary Gear Bearing)

I only have the meassurements of the excentric shaft and the old bearings, but how does this help me in identifying the correct ones, since there is only a clearance stated, not the inner diameter?

Here are the meassurements:

Excentric shaft, rotor bearings
front 73,98mm
rear 73,98mm

Excentric shaft, main bearings
inside rear 42,97mm
outside rear 42,945mm
inside front 42,87mm
outside front 42,945mm

Rotor bearings
front 74.04mm
rear 74.05mm

Main (Stat. gear) bearing
rear inside 43,05mm
rear outside 43,06mm
front inside 43,05mm
front outside 43,05mm

I would highly appreciate any advice!

 

the E shaft is actually stamped with the bearings they used at the factory.

or

the number mazda gives 1.980mm is the thickness of the bearing. the 2mm bearing is 0.02mm thicker than the 1.980mm bearing.

or

since the biggest and smallest are only 0.02mm apart, it doesn't really matter too much.

or

sometimes you can see the color code on the old bearing, its on the end of the shell.

 

I believe the old ones are yellow, but there are 2 yellow ones:
NF01-10-E220 (Yellow 1.988mm)
and
NF01-10-E040 (Yellow 1.980mm)
Also, there is good possibility, that the bearings where changed at the last rebuild, which was only 5000 miles ago..

 

Is it correct that it would be a safe bet to buy the blue 2.000mm Bearings?

Or would it be better to buy the ones Mazda used at the factory? Where is the number of the bearings stamped on the e-shaft?

We are talking only about main bearings here, right? What about the rotor bearings? Are these the right ones (3mm?)?
RHDJapan : Mazda OEM Rotor Bearings 3mm - N3A111B11

 

No suggestions?

 

can you even measure 0.02mm?

 

Pretty easily... 0.02mm is pretty big in the world of hydrodynamic lubrication. For reference, RB26 main and rod bearings tolerance groups are 0.001mm +- 0.001mm. That's a bit harder to measure

 

Can you post pictures of the old worn bearings.

 

Pictures can be found here:

https://www.rx7club.com/3rd-generati...heavy-1099266/

And yes, I can meassure 0.02mm. But thats not the point, the point is I "invest" in bearings and want to buy the right ones. Of course its not much of a difference, but if it is really the case that the bearings have been changed in the last rebuild, they where fucked up in only 5000 miles. So I can't be sure if it is possible to buy the absolute wrong ones.

 

All the clearances are listed in the FSM around the inspection section of the engine FSM. Page C-51 or thereabouts. Take the difference of the inner diameter of the bearing and the outer diameter of the appropriate E shaft section and you have your clearance.

Matt

 

I'm sorry, I don't get it. If I only have the clearance and not a diameter as a reference, I can't calculate the needed inner diameter of the bearing. Do I miss something here?

 

You need a good micrometer to properly measure the lobes. I use a Mitutoyo in the shop. That being said, most motors I build end up receiving the largest yellow stamped bearings as there is more room for oil retention.

 

Largest inner diameter, so 1.980mm right? What if the e-shaft has allready some wear? Isn't the clearance to big than? Does anybody know the OEM diameter of the e-shaft?

 

Yellow are the largest bearings and will provide the most clearance. Eshaft diameter will vary. The FSM lists the specs for each lobe and total runout.

 

No it doesn't, or at least I didn't found it. Thats my whole problem here! I have only found the clearances, so I have no reference.

 

Atkins only sells one option:
NF01-10-E04 (Main) Yellow 1.980mm
N3A1-11-B11 (Rotor) 3mm
So should I just take them and don't bother too much?

 

Page C-53 of the fsm. You will be fine with the yellow stamped bearings.

 

Thanks, but there's just the clearance, nothing to reference when searching for the needed thickness of the bearing. But I finally got my head around this, thanks to a friend: I have to press out the old bearings, meassure the thickness and can then calculate the needed thickness of the new bearings to meet the clearances in the fsm, since I allready got the clearance with the old bearings.

Can anybody tell me the outer diameter of the tools needed to press out the bearings? I will have a shop machine them for me. When this doesn't take too long, I will meassure the old bearings, otherwise I will just order the yellow ones.

 

Just buy the oem tools or the ones by atkins. They aren' too expensive.

 

Yes, but they take a considerable time to get here, I don't have that time.

EDIT: The inner diameter of a new yellow bearing would be sufficiant, too. (Both rotor and main)

 

use the largest one u will be fine.

 

From all of your questions, you would be way better off in sending your motor to IRP and stop worrying. Go for the best quality instead of saving money!

 

Building his first engine...priceless
For everything else..Visa

 

If you don't have stat gears and rotors to measure, I think nopistons did have dimensioned drawings for the tools you need to turn a long time ago....if you want to look. I just go for the bearing with the biggest oil clearance, as per IRperformance.

Have seen letter stamps between the two lobes on the eccentric shaft, BB and YY is common, I'd guess the B could mean the "up" size and Y is probably yellow - could be just like the gibberish on the rotor sides too!