Topic: CB 500 main bearings

[sgd37]

Hey,

Can anyone tell me if this misalignment between the oil hole and the main bearing in the top crankcase is normal. http://imgur.com/LxjL6BJ

Also should I be worried about these scuff marks on the top left of the bearings
http://imgur.com/NDqIrCG
http://imgur.com/ioBMEiX

Cheers

[sgd37]

Why so quiet? If it's a stupid question tell me but otherwise Id really appreciate some input. Someone must know if these bearings are good to reuse.

Thanks

[flybox1]

I would reuse those bearings.
I think you're ok as long as its not fully blocking the oil passage.

[sgd37]

Great thanks for the reply

[Ridem32]

I would not reuse them. The scuff marks look bad to me. And the oil hole should line up.  You can get new bearings from David silver spares.  Do they still have the color mark on them?


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[HondaMan]

The best way to test them (and the only method I use) is to Plastigage them. This will tell you if the clearances are correct. This engine runs well with clearances out to 0.0028", beyond that you must use heavier oils or newer bearings.

To Plastigage this engine, you lay the crankshaft in the upper case, lay the Plastigage along each crank journal (about 3/4" of it is enough) and then close up the bottom case and torque the 10 bolts down to 18 ft-lbs. Then open it back up and measure how far the Plastigage spread, using the gages printed on the Plastigage sleeve. Then clean it all off with a rag or fingernail, re-oil everything if good, and reassemble it all.

[Ridem32]

I agree about the plastigage. But looking at those bearings I would replace them now while you have the motor down. I would never use a scuffed up bearing. JMO


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[sgd37]

Thank you hondaman for the advice. I did plastigage them as you said and they are all around 0.002" or less. The scuff marks are a worry but can anyone give me an explanation as to why they shouldn't be used. As far as I can tell they haven't cut through the white metal.

On another note I was thinking of mixing up my own assembly grease as a mixture of oil, molly and 400 mesh graphite. Alternatively I could fortify some assembly oil/grease with graphite. Any thoughts on that? 

Much appreciated as always.

[Ridem32]

Use white grease on your build.  Again: I would install new bearings. Good luck with it


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[flybox1]

Thank you hondaman for the advice. I did plastigage them as you said and they are all around 0.002" or less. The scuff marks are a worry but can anyone give me an explanation as to why they shouldn't be used. As far as I can tell they haven't cut through the white metal.

On another note I was thinking of mixing up my own assembly grease as a mixture of oil, molly and 400 mesh graphite. Alternatively I could fortify some assembly oil/grease with graphite. Any thoughts on that? 

Much appreciated as always.

Those are within tolerances, and could be reused.  Up to you.
Redline Assembly Lube is also good.

[HondaMan]

I use 20w50 oil for assembly lube, lavishly. It washes out immediately upon oil-up, which I do with the electric start (and no sparkplugs installed) on these engines.

Scuffs: I have disassembled these engines (high mileage) to find such things as GROOVES carved into the bearings by some casting flash that made its way into the bearings right after the engine was started (new), leaving the aluminum buried in the soft bearing. And yet, the engine went many tens of thousands (even over 100,000) of miles in this condition with no ill effect. When you realize these bearings are as wide as the ones in my old Ford 390 V8, 400 HP engine's rod bearings, which ran well over 250k miles before I lost the car (to my brother wrecking it) with half the oil PSI of these engines, well...it is hard to imagine that a scuff like this would be significant?

These engines are seriously overbuilt for the power they generate.

[sgd37]

Thanks HondaMan you're my hero

Do you think it would be ok to run 15w40 at average temperatures?

[HondaMan]

Thanks HondaMan you're my hero

Do you think it would be ok to run 15w40 at average temperatures?

Sure, in this engine. In the 750, that's getting pretty light. Just be sure to use oil that has little (or NO) detergent, and if it doesn't have zinc, add some. You can find ZDDP additive in little 4 ounce bottles: use 1/2 bottle at each oil change, that's enough.

If you decide to tour Arizona in August (like my brother and I did in 1978), maybe think about getting 20w50 in it before that trip: his 500 got so hot (using 20w40) it temporarily seized and stalled when we pulled off the hiway to a stoplight in 110 degree weather, and we had to cool it down about 10 minutes before the pistons stopped dragging enough to let it idle again. We changed it to 20w50 the next day and it was fine after that for the rest of the trip.

[sgd37]

Interesting. Are you saying that the filter on the 500 cant handle the load, otherwise why would i want sludge in the engine?

[HondaMan]

Interesting. Are you saying that the filter on the 500 cant handle the load, otherwise why would i want sludge in the engine?

Well, in these engines you need low-detergent oils because it foams when whipped by high-speed parts. In the 750 this is due to the crankshaft weights: in the smaller Fours it is because the tranny gears are sitting right in it. That whips it into a foam. This reduces the oil effectiveness and lowers the oil pressure. Also, you need zinc in the oil (specifically for the rocker arms and the clutch), which often is not found in automotive oils today. The EPA outlawed it in 2002 to protect certain catalytic convertors on certain imported cars, now it is real hard to find oils with zinc. Usually they are labelled as "offroad use only" today, but they are still around, so read the labels carefully, or do some website research. Oils we know that work are Bel-Ray's Mineral EXL type, Spectro (Golden), and some of the diesel-rated oils.