Topic: pitted bearing shells - should i replace ?-updated with bearing charts

[shinyribs]

The engine is a 750 out of a 78K.  Low miles at 16k miles. It got stored with a plug out and dirty oil in. The plug being out caused for a rehire, but I'm undecided on the main and rod bearings. I suppose the acid in the oil caused thus. No flaking, just a little pitting. Heavier on the mains than it is on the rods.

[Old Scrambler]

Usually I would replace the shells because the metal may be brittle.  Minor pitting may increase the amount of oil held in the bearing....but also tends to hold dirt. Since you apparently have the motor torn down to a bare crank, new shells are relatively inexpensive and be sure to clean the crank-journals.

[Jerry Rxman Griffin aka MuthaF'er]

Yes or no, it all depends.

[Retro Rocket]

Yes or no, it all depends.

Each way bet there Jerry....

[shinyribs]

LOL yeah, that sounded totally noncommittal

Ill put up some pics in a bit. Where's a good source for these things. I'm still sorting out the voodoo on the sizes, but I have one rod I can't make out bummer

[lucky]

Ask yourself.....If you were a professional shop mechanic and and a customers bike had pitted bearing races would you replace that bearing? OF COURSE!!

[shinyribs]

I agree Lucky. When I was fooling with drag cars it was no expense spared...not so much anymore

The mains are shot.No doubt about that. Here is a pic of one rod. All four look pretty much the same.

I figured ( and I know this is probably bad logic) that the bearings in this motor look very much like the ones in my other two bikes. My 76F sat for 4 years,the chopper sat for 25! years. Chances are there is some acid pitting inside those motors,too. The 76F has proven pretty reliable,racking up over 10k miles last year.

Anywho. Pics. Let me know what ya'll think. Thanks!

[brandEn]

LOL yeah, that sounded totally noncommittal

Ill put up some pics in a bit. Where's a good source for these things. I'm still sorting out the voodoo on the sizes, but I have one rod I can't make out bummer

The cheapest place I have found is Service Honda
http://www.servicehondapsn.com/fiche_select.asp

[shinyribs]

Thanks for the link! I got a new bookmark now! But WOW! $11-12 per bearing half?!?! Ouch

[Jerry Rxman Griffin aka MuthaF'er]

Yeah, pricey multiplied X 8 then again for the crank.

IMO those look close to new. I see a couple flattened spots that may well be/have been minor specs of aluminum that made their way in and got squished. Plastigauge them and reuse if good. Or spend $100 for perhaps the same results.

[bryanj]

Thats not Acid its crap in the oil that wasn't changed often enough---Oil that is not crap

[Retro Rocket]

Thats not Acid its crap in the oil that wasn't changed often enough

Yep acid....

[dave500]

the idea of the soft lining on the shell is to actually embed any debris and not force it against the journal,this is fine for normal break in type debris,yours look good,ive used many of the factory bearings in engines so long as they arent damaged,roller bearings just crush this stuff up and rotate it into grinding paste,i remember seeing a tv show ages ago it might have been merlins back in the day,it was old black and white?they run them then strip them and fit new bearings,then run them longer for a time at half power for so long,then strip and inspect then run them at half power then full power for so long,,then theyve passed,then they flew and got shot down after all that?

[faux fiddy]

the idea of the soft lining on the shell is to actually embed any debris and not force it against the journal,this is fine for normal break in type debris,yours look good,ive used many of the factory bearings in engines so long as they arent damaged,roller bearings just crush this stuff up and rotate it into grinding paste,i remember seeing a tv show ages ago it might have been merlins back in the day,it was old black and white?they run them then strip them and fit new bearings,then run them longer for a time at half power for so long,then strip and inspect then run them at half power then full power for so long,,then theyve passed,then they flew and got shot down after all that?

I'm glad we have hondas instead of more zeros...

Yeah, pricey multiplied X 8 then again for the crank.

IMO those look close to new. I see a couple flattened spots that may well be/have been minor specs of aluminum that made their way in and got squished. Plastigauge them and reuse if good. Or spend $100 for perhaps the same results.

Yeah, you need those new repro valve keepers.  But  save the old ones for spares  Just so you can  when you drop a valve open it up again  and put them back.

[shinyribs]

Thanks for the replies. Junky pics,I know. It's hard to really get a good pic of these things. But the little pinholes and divots you see in the bearing is not embedded debris,but pinholes and divots.I assume caused by acid in the oil eating away at the bearing.Maybe not

[Old Scrambler]

You may be able to replace the bottom-end and cases from another motor for less than piecing this back together.  Its all a risk but spare parts are good

BTW....nice job on the alloy rims

[shinyribs]

It's always a balance between spending to repair something ,or starting over with something new   I think the rod bearings will be OK,so I'll just need mains.

But I'm having a time figuring out the bearing sizes. My case is marked BBBBB. But I see no markings on my crank. Of course,I have no idea where to look for said markings,or what they even look like I only have half of the equation. I hate to just slap greens in there and rock it. Just seems like you're cheating,but it's what I may have to do.


Thanks on the rims! I'm real happy with them

[brandEn]

Those markings on the crank can be nearly impossible to see sometimes. You need to know what to look for and then get it the right light and angle and make sure its clean.

Check out this thread to give you an idea of where they are at. It has a decent pic.
http://forums.sohc4.net/index.php?topic=84715.0

another
http://forums.sohc4.net/index.php?topic=28774.0

Just remember those markings where made by hand with a scribe and are just scratched in. One crank I had looked like a bunch of X's but they were all A's. B's might look like 3's.

[shinyribs]

AWESOME! Thank you! I happened to be in the house eating lunch and saw your post. I've hunting them for days wil no luck,now they're as clear as the nose on my face!

AAAAA 4444   plain as day    :DThanks again!

[brandEn]

AWESOME! Thank you! I happened to be in the house eating lunch and saw your post. I've hunting them for days wil no luck,now they're as clear as the nose on my face!

AAAAA 4444   plain as day    :DThanks again!

SWEET!

[crazypj]

Is the pic of the best or worst bearing?
I would change that pair although they probably all need changing unless you intend to sell it and rip someone off?
 They show witness marks as well as embedded particles, not good, going to need some major cleaning out

[shinyribs]

That is the worst of the rods. Again,the spots you see are not embedded particles,but holes or divots. I suppose it is where the acid in the dirty oil ( I pulled pine needles out of the oil pan )ate the bearing up after sitting for a long period of time.

For the record,I would never sell anything with the intention to rip someone off. I'm not saying that you accused me of that,just wanted to make that clear. This is the engine destined for the bike in my build link,so it's a keeper.

Keeper or seller,I'd build them both the same.

[shinyribs]

Where can I find the chart to figure out which bearings I need? I've searched the forum,but with no success.

 My crank is pristine and out of a known original 16k miles engine.Never been opened before. I bought the bike from a friend who bought it from the original owner.Both are reliable in telling me it's never been apart. So I should be able to use the factory markings and install bearings according to those. If not,I'm open to any and all ideas.

May case is marked : BBBBB
Crank (thanks branden!) is marked: AAAAA 4444
My rods are marked:
Rod #1-1
Rod#2-3
Rod#3-3
Rod#4-2

Not trying to get ya'll to do my homework for me. But if anyone would like to check behind me I'd greatly appreciate it

[bryanj]

Table is in the parts book i have but it shows the crank mains(5) as numbers not letters and big ends (4) as letters not numbers also biggest number is 3 so i am confused

[shinyribs]

What parts book would that be? I have a pdf of the Factory Service Manual,but I didn't see it in there.