Topic: replace main bearings 400F ?

[dud]

Hi,

I've got a 400F with about 41000 miles on it.  I'm replacing the pistons
with two sizes oversize, I've had the cylinders bored to match.  Also
replacing cam chain, tensioner, and guide.  I'm now trying to decide if
I want to replace the main bearings.

1. bearings "look good" but my mechanic says they also look like they
have the mileage on them.
2. The case has BAAAA stamped on the back, which I understand is
a magic factory code for the 5 journals.  Does anybody know what those
letters correspond to?  I'm trying to avoid the whole plastigauge circus.
3. The bearings have "D50-A STD" stamped on four of them, and the one
that corresponds to the "B" journal has "D51-A STD" stamped on it.  Does
this mean anything to anybody?

General advise on the main bearings (or the motor rebuild in general)
as well as specific answers welcomed.

Thanks,
BIll Dudley
SOHC4 #25

[Bodi]

Avoiding the plastigauge "circus" to do a whole lot more work and spend a lot of $$$ when both might be wasted makes no sense.
The best information I have is that the codes on the block meant something at the factory but mean nothing to you and me.
The only correct procedure is to plastigauge the bearings to see if they are in spec. If not, you have to measure the case bores and the crank journals and use the bearing chart in the shop manual (or parts list) to select the required shells. Then you have to try and find the shells you need (good luck).
You already have the engine cases apart if you're doing the tensioner guide and chain. Gauging the bearings takes an hour at most.

[bryanj]

You need the codes of the crank to cross reference the two together and get the shell sizes. The letters/numbers on the back of the shells mean absolutely nothing! Cross refering the letters for shells is explained well in the original Honda manual