Topic: Brown, Green & Yellow Bearing Marks...........wtf??

[rhos1355]

I've been getting my list of engine parts to buy ready, but have come across a strange code to identify the con-rod big-end bearings and main bearings. They're described as either Green, Brown or Yellow. I have no idea what this means so I looked up the parts book and lo and behold I found this:




and now I'm even more confused. Can somebody explain to 'ol thicko here what I should order.
The crankshaft journals are well within wear tolerance and do not require grinding so I wanted to just replace the old ones with standard new ones.

cheers

[HondaMan]

Well..."Standard new ones" were Yellow, Green, Brown or Black (in declining clearance values), depending on the crankshaft pin size and the bore size for the rods and crankcases. The old ones will have the color on the sides of the bearings, and the engine cases will show the bore sizes, while the rods and crankshaft will show their related hole/pin sizes, too. Then you look those up, cross reference from the chart, multiply by 10 if you have Honda's original (and erroneous) service manuals, and then select the bearing size.

The bearings in these engines, unless physically damaged, last a LONG time. Honda's service limit is .0032", stock new ones, properly selected against their holes & pins, were .0008" to .0012" when new.

If yours are less than .0022" clearance, I would recommend using the ones you have. Once they wear past about .0025" clearance, the oil flow to the top end begins to drop off because of the leakage in these bearings. These engines run smoothest, and with the most midrange power, when the original bearings have worn themselves in to about .0018" clearance because they have aligned themselves with the twisting and angles of the original crankcases. This was a point that was never taken lightly by roadracers in the day: engine builders today have the advantage of being able to align-bore the cases a few tenths of thousandths to make this happen at startup: in those days you had to just "ride it in" to loosen them up. 

[rhos1355]

Cheers Hondaman, I'll check the info on the crankcases etc tonight when I get home from work. No doubt I'll be back with more questions.

[CB750F2]

On the crankshaft adjacent to the primary chain sprocket there are some numbers and letters. So for the crankpins you should see something like L:3343. This means that the number for No 3 crank pin is 4 and the rest are 3. On each connecting rod bearing cap you should see a number like 1 or 2 or 3. So if you wanted to know what bearing colour to use for No3 crank pin and the number on the connnecting rod bearing cap was 2 then using your chart a green bearing would be selected. There is also a chart for the main bearings. This chart uses letters. Again these letters are marked on the crankshaft and on the crankcases. The crankcase letters are marked on the front left of the upper crankcase and if the motor is still installed in the bike you need to lie down under the bike a look up - a torch would be handy. The service manual should show you this. Once you know what letters you have then use the chart in the service manual. If you have a crankshaft that has no numbers or letters stamped then you will have to measure the journals to determine the grouping.
          I suggest that you simply inspect the bearings and journals and if they appear to be in good condition check clearance using plastic gauge. If the clearance is well within the service limit reuse. Even if you use the chart and replace all bearings I would still use the plastic gauge to check the clearances.
          There is also a letter painted on the connecting rod bearing cap. This is a weight indictor. The letter should be the same for all connecting rods. Pat

[Bill/BentON Racing]

You guys nailed it,clearances OK,not at upper limits,put that baby back together.I replaced mine originally,plastigage,manuals are wrong @ times,plastigage doesn't lie.Ran 3 seasons w/this bottom end ,had it apart once again(fix tranny)It looked and measured fine.Ran 13,000+ with this set up.Bill

[HondaMan]

You guys nailed it,clearances OK,not at upper limits,put that baby back together.I replaced mine originally,plastigage,manuals are wrong @ times,plastigage doesn't lie.Ran 3 seasons w/this bottom end ,had it apart once again(fix tranny)It looked and measured fine.Ran 13,000+ with this set up.Bill

Similar:
In 1980 I measured mine at .0016" clearance average, with 55k miles on the engine, so I just reassembled it. In 2005 I tore it down for another look, found the worst one to be .0019" clearance at 128,000 miles, reassembled again. I bought a full set of bearings, next step down (they come in steps of .0004" smaller diameter), and when I reach my (personal) limit of .0020" I'll install the new ones, which will take them back to about .0016" again.

[NickC]

Its good to know these bearings last. I'm replacing two of them with small knicks (crank is ok) So for the crank bearings, i just go off the letters stamped on the back of the case?

[rhos1355]

Sorry guys, just to get me on the same hymn page as you:

Pin = Journal?
Crank pin = Con-rod Big end (crankshaft end)?
Main Bearing = Crankcase bearing?

If I'm getting any of these arse-about-face let me know.

[MCRider]

Sorry guys, just to get me on the same hymn page as you:

Pin = Journal?
Crank pin = Con-rod Big end (crankshaft end)?
Main Bearing = Crankcase bearing?

If I'm getting any of these arse-about-face let me know.

that's about it. Wickipedia to the rescue:
http://en.wikipedia.org/wiki/Crankpin
http://en.wikipedia.org/wiki/Main_bearing

[MCRider]

Its good to know these bearings last. I'm replacing two of them with small knicks (crank is ok) So for the crank bearings, i just go off the letters stamped on the back of the case?

Can't go by those alone, need the codes onthe crankweitght and the chart in the manual. IF you're OK with dimensions, just use the color on the side of the shell.

[rhos1355]

On the crankshaft adjacent to the primary chain sprocket there are some numbers and letters. So for the crankpins you should see something like L:3343. This means that the number for No 3 crank pin is 4 and the rest are 3. On each connecting rod bearing cap you should see a number like 1 or 2 or 3. So if you wanted to know what bearing colour to use for No3 crank pin and the number on the connnecting rod bearing cap was 2 then using your chart a green bearing would be selected. There is also a chart for the main bearings. This chart uses letters. Again these letters are marked on the crankshaft and on the crankcases. The crankcase letters are marked on the front left of the upper crankcase and if the motor is still installed in the bike you need to lie down under the bike a look up - a torch would be handy. The service manual should show you this. Once you know what letters you have then use the chart in the service manual. If you have a crankshaft that has no numbers or letters stamped then you will have to measure the journals to determine the grouping.
          I suggest that you simply inspect the bearings and journals and if they appear to be in good condition check clearance using plastic gauge. If the clearance is well within the service limit reuse. Even if you use the chart and replace all bearings I would still use the plastic gauge to check the clearances.
          There is also a letter painted on the connecting rod bearing cap. This is a weight indictor. The letter should be the same for all connecting rods. Pat

Chhers, Pat. I checked out all the numbers & letters stamped or engreaved on the crankcase, con-rods and crankshaft, cross referenced them on the 2 tables in the parts manual and came up with Green. Unfortunately I'm at work right now but I'll post tonite showing all the letters etc jus t to see if you come to the same conclusion as I did. Rob

[Bill/BentON Racing]

Sounds like you have it figured out,this used to stump most techs in the shop.Follow Pat's advice ,if you replace check em,takes a little longer,but worth it.Bill

[MRieck]

On the crankshaft adjacent to the primary chain sprocket there are some numbers and letters. So for the crankpins you should see something like L:3343. This means that the number for No 3 crank pin is 4 and the rest are 3. On each connecting rod bearing cap you should see a number like 1 or 2 or 3. So if you wanted to know what bearing colour to use for No3 crank pin and the number on the connnecting rod bearing cap was 2 then using your chart a green bearing would be selected. There is also a chart for the main bearings. This chart uses letters. Again these letters are marked on the crankshaft and on the crankcases. The crankcase letters are marked on the front left of the upper crankcase and if the motor is still installed in the bike you need to lie down under the bike a look up - a torch would be handy. The service manual should show you this. Once you know what letters you have then use the chart in the service manual. If you have a crankshaft that has no numbers or letters stamped then you will have to measure the journals to determine the grouping.
          I suggest that you simply inspect the bearings and journals and if they appear to be in good condition check clearance using plastic gauge. If the clearance is well within the service limit reuse. Even if you use the chart and replace all bearings I would still use the plastic gauge to check the clearances.
          There is also a letter painted on the connecting rod bearing cap. This is a weight indictor. The letter should be the same for all connecting rods. Pat

Chhers, Pat. I checked out all the numbers & letters stamped or engreaved on the crankcase, con-rods and crankshaft, cross referenced them on the 2 tables in the parts manual and came up with Green. Unfortunately I'm at work right now but I'll post tonite showing all the letters etc jus t to see if you come to the same conclusion as I did. Rob

I use  greens for mains and rods 90% of the time.

[Bill/BentON Racing]

MR nails it again!! Green by far most commonly used.Bill

[MRieck]

MR nails it again!! Green by far most commonly used.Bill

Thanks Bill. I have had to use yellows with Carrillo rods as they are manufactured with the absolute minimum big end ID....that is common for all Carrillo bike rods(at least that's what I've found). Hondaman's post sum it up well in regards to main bearing clearance numbers. I like to have bearings on the loose side as it will pass more oil and keep the bearing cooler. Cooler bearings last longer and you don't drive the oil pump so hard. I'm not so worried about loosing pressure to the top end....you'd need a pretty good size drop in pressure to screw the top end pooch.

[Jerry Rxman Griffin aka MuthaF'er]

It's just SOOOOOOOO refreshing to see someone find and read the engraving on a crank right off the bat   

[rhos1355]

It's just SOOOOOOOO refreshing to see someone find and read the engraving on a crank right off the bat   

You kidding? Took me 1½ last night fiddling around with the flashlight etc. Take my glasses on, put them back on again, shine the light this way, then that way. In the end I spread some talcum powder on it and that enhanced the engravings abit.
Found the crankcase stamps almost by accident, just picked the first one up and hey presto, there's BBBB   B  stamped on it. Figured this is what the lads are telling me about. Then I had to fish out the con-rods from all the crates of spares. Check the numbers, put everything back again. Who said this sohc-4 disease is easy

[MCRider]

It's just SOOOOOOOO refreshing to see someone find and read the engraving on a crank right off the bat   

You kidding? Took me 1½ last night fiddling around with the flashlight etc. Take my glasses on, put them back on again, shine the light this way, then that way. In the end I spread some talcum powder on it and that enhanced the engravings abit.
Found the crankcase stamps almost by accident, just picked the first one up and hey presto, there's BBBB   B  stamped on it. Figured this is what the lads are telling me about. Then I had to fish out the con-rods from all the crates of spares. Check the numbers, put everything back again. Who said this sohc-4 disease is easy

At least yours were there. Mine, and many others, are long gone with the machinists tool from lightening the flyweights. Hence the reliance on plasti gauge and the colors on the existing bearings.

[rhos1355]

Right, here's the numbers/letters I fished out last night from all the bits;

Crankshaft =  J L AAAAA    P L3443

On Crankcase = BBB B B

On Conrods = 2 (all of them)


So looking at the Con rod Table


and at the Crankcase bearing table


I deduct I require Greens for all bearings.

Correct?

[CB750F2]

I agree with GREEN but make sure you use the plasti gauge to confirm that your clearances are within specs. For new bearings I like to aim for 0.0015" and for used bearings 0.002". I also suggest that you re-read Hondaman's reply to your post. Pat

[754]

The manuals give a pretty clear explanation where to look.

I dont think anyone should be attempting bearing replacement, without reading (As many times as it takes) & UNDERSTANDING how these are graded and what the  marks tell you to use.

[Bill/BentON Racing]

Amen brother,way too much invested to guess,take your time it will work out,like MC said you still got your markings!Bill

[NickC]

Anyone have a source for the main bearings?

[MCRider]

Anyone have a source for the main bearings?

I got mine at BikeBandit.com. Paid too much.

Hondaparts-direct is/was cheapest but is "closed" and not taking orders. Could be a connection there.

Motogrid.com has them at reasonable prices, lower than bikebandit.

[rhos1355]

Right folks, I've measured the con-rod and main bearing clearances and found them to be 0.002" which according to the book is within tolerances. But the 3rd main bearing is well scoured. Maybe some detritus left in the oil over its 30+ year history.
So I've bitten the bullet and ordered as much stuff as I could afford to start rebuilding the engine. I feel a little queasy at this point. Mainly because of the amount (£360+) but also because comparing last year's prices, when I should have ordered them, they've gone up approx 10-15%!
Anyway, I wish to thank you all learned folks for all the very usefull input and information you've given me on this issue. Many thanks.


Rob.