zmaniv

The machine shop I took the crank to wants to know what the journal sizes are supposed to be.
I cant find it in the manual all I can find is the oil clearance.
Anyone have the main journals and connecting rod size?

RCVTR

Don't do any machining on the crank. The wear on the crank will be immeasurable in the life of the engine. Every one I've measured was perfectly round and not tapered. That's why Honda doesn't publish wear specs.

Just replace the bearings according to the codes on the crank, rods and cases, then measure clearance with a plastigage, to be sure the bearings are correct.

Take your crank from him and don't let him touch it!!! Rods too!! Although you may want to measure rod twist.

RCVTR

On another note.

If you are going to have a machine shop hone your cylinders, you will most likely end up with too much skirt clearance on your pistons. It's already going to be on the high side.

I would recommend a light deglazing with a ball hone or 800 grit sandpaper on a sanding pad with WD40. This will give you a light crosshatch for oil retention and ring break in.

zmaniv

What about the scorched area on the crank pin journal?
Would you recommend a light polish?

RCVTR

Do you have some scoring? I'm not sure what you mean by scorched.

You can do some polishing with fine crocus cloth. I've even done a lap with a leather strap. But I wouldn't worry too much about a mild scoring. If there were any impurities in the oil, they should have imbedded in the bearing babbit and damage should be very minimal.

If you have a damaged crank, you will have to replace it. I don't think you'll find OS bearings.

zmaniv

scorched crank pin

Hawkrider

Here's my recommendation: Look at the bearing. If the crank wore all the way through the soft bearing material (babbit, copper, or whatever) and into the harder base metal then there's probably damage and you should replace the crank. If the heat discoloration is consistent all the way around the bearing then that is probably a sign that it's not out of round.

RCVTR is pretty knowledgeable about these motors. Take his advice for sure.

gboezio

Damn, I'm pretty sure that to clear this out, you will need undersize bearings,
I just checked and yes there are many thickness available, there is a color code on the rod bearings, just order a thicker bearing, just polish the crank until it's clean, measure the difference and select the proper bearing thickness to match what you removed.

RCVTR

Ouch. That was hot. Probably wanted to spin the bearing.

I would measure the journal near both ends carefully with a micrometer (don't use a caliper!)

Measure in 2-3 places around the journal at both ends (scorched and non-scorched) and in the middle-take a bunch of measurements. If you can't measure a difference, it's probably ok. The one side looks fine.

Polish the surface with some very fine crocus cloth, by hoding both ends of a long strip and pull it back-and-forth shoeshine style.

Put it together. check the bearing clearances (use the old rod bolts for this!) Put new rod bolts in. Torque them to spec. and run it with confidence.

It looks like the main journals could use some polishing as well. It will remove negligible material from the journals

zmaniv

Thanks everyone.

Here is what I got from Roger Ditchfield

Dear Martin,
You were correct about the manual only giving clearances and not dimensions.Ihave spoken toHonda Technical and they do nothave the info either. Therefore you are going to have to determine whether the crank etc is salvageable by using the following procedure.Please do not think I am insulting you or your engineer by giving you this procedure.
1) Clean the shell material off the crank journal.As this is soft metal itwill come off turned slowly in a lathe with Emery paper or metal scraper
2) Measure with micometer across four axis to determine that it is still round
3) Clean the soft shell material from the con rod
4) Measure across four axis to deternime it is still round - you can compare the other journal and rod to give you a clue
5) If all is well then using the manual procedure to determine what shells should be used as standard and purchase them
6) Follow the Plastagauge procedure to determine if oversize shells will bring it back to tolerance

Worst way you waste a set of shells
You must check the other rod and journal
What caused the shell to spin in the first place?

Hope this helps

Regards
Roger


Should we add this to the knowledge database?

RCVTR

Also...

I would be investigating to try and determine what caused the problem. Something was going seriously wrong.
Was it run out of oil?
What does the wear pattern on the main and rod bearings look like?
I doubt the rod is bent, but I would check it.
How do the cam bearings look? Check the clearance on them as well.
Might as well measure the cam lobes, too.
If it had a lubrication problem, look for other signs of damage, especially in the top end.

RCVTR

No insult here!
It's good to see feedback from a pro.

hawxter996

zmaniv has another post on this forum where he purchased this engine.
i do believe it was run low on oil.

gboezio

That would explain such damage.

A bent rod will cause damage to the outer portion of the bearing, it's riding sideways, pushing one edge on one side and the other edge on the other side.

zmaniv

The cam bearings look great as well as the lobes.

zmaniv

I posted the same question several places. I wanted to get a response sooner rather than later.

hawxter996

thats great! hope you get it together soon.

RCVTR

You might want to check the lofter clearance and bore surfaces too.

the easy way to check them is to slide the clean lifter into the bore, grab the top and move it front to back and side to side. it should be free but not sloppy - the same in both directions.

Good lifter bores:

Hawkrider

You mean "valve guides"?

RCVTR

Nope. Valve guides aren't visible.

Lifter bores are probably ok. they don't see the loads that the main and rod bearings do.

RCVTR

I'm not as knowledgable as some. I've been through them (or RC51) 3 times and paid attention to details.

If you can put the crank in a lathe with a live center at the outboard end, you should get a more consistent polish on the journal. Turn it prety slow, because it will shake like a motha.