225 Dauntless rod and main bearings

I pulled the motor apart today and all in all, it looks good. I'm looking at the rod and main bearings to see if they are standard or undersize. The only markings on the rod bearings are the #'s 27Z7 on one side and 57432 on the side with the notch. Also under the 57432 are the letters GMMA, but no std. or undersize markings. The main bearing has what looks like 85M9 on the tab side and 57896 on the other side with the GMMA under it. Can anyone tell me what I have? I'm assuming they are standard?

 

Don't assume. Get yourself some plastigauge and check em to make sure.

 

robbe, I would GUESS that they are standard. If they are undersized the USUALLY are marked on the bearing after the part number with a m010, m020. There were some aftermarket suppiers that did not mark the bearings that way.

I WOULD measure the journals with a micrometer before ordering the bearings. Check for size, out of round, and taper.

Then when I am installing the bearings I would use plastigauge to double check the clearences. Plasigauge measures the clearences it will not tell you if your journals are undersized or standard.

Note: I also check the main bearing bores with some snap gages and a micrometer. I bolt the caps on at the maximum factory torque specs, and then measure them. I do the rods the same way. I also check the rods for twist. The tooling to do the twist test is fairly costly.

If this is something you are unable to do for some reason, a trip to your local machine shop will get you the proper info and peace of mind.

IHTH, Matt W.

 

Don't even need a mike to determine if the crank is ground. Even a cheap quality caliper will usually get you to .001-.005". Just don't use it to set bearing clearence. Like Patrick said, need to measure journals.

 

Don't use Plastigage for anything...

 

Yeah, I mis-spoke, thanks for the correction. Dunno what I was thinking.

 

Thanks all. I knew that I could use plastigauge for clearances but needed to know if all was standard before ordering parts. Every motor I was ever into,( maybe 6 or 8 ) had std. or under sizes stamped on bearings, this one didn't. Just trying to get all the help I can. Now, can anyone tell me what the journal size should be for an unground crank? All journals look and feel smooth, but no time like the present to make sure. Thanks again all.

 

Mains 2.4995" Rods 2.0000"