Topic: 78 CB 550K motor rebuild

[flatlander]

I only know of a measurement to be used for warp. Didn't see anything about the thickness in the manuals I looked in.

i don't remember them giving a thickness for the steel discs. which makes sense as the friction plates are softer and wear earlier.

this thread is about a modified clutch but may include some useful info for you: http://forums.sohc4.net/index.php/topic,145565.0.html

[AlekStooge]

Thanks for the link. Comparing the manual to CMSNL I realized the top disc is supposed to be stock then all the other discs. The manual makes no mention of it.

[AlekStooge]

Installing the cylinder studs. I was going to ask should I use some Loctite....but this apparently says use a bit of oil. Is oil the way to go?

http://forums.sohc4.net/index.php?topic=81179.0

Also, for the torque spec can I just tighten the double nut?

[AlekStooge]

I need a little help installing my pistons. I learned a little bit in the class I took.

First, lets make sure I understand which rings go where and how.


The first ring on the left is the oil ring expander that goes on the bottom grove. I'm not sure what the next two rings are? The ones on the far left are the oil rails that go above and below the oil ring expander, right?

I don't really see any kind of markings or bevel like the instructions that came with the ring mentioned. So I'm assuming I can install them either way up or down? When I took the class I was told there might be an R on one of the rings indicating which way it goes but the only thing I see is N100 on the ring next to the expander. I'm guessing that is just a manufacture code.

I learned the rings should be staggered like a Y, and none of the gaps facing the exhaust side. The manual says stagger them 120 degrees and none at 90 degrees from the wrist pin. Is this correct and is it only referring to the top and second ring or all?

Will I absolutely need a ring expander tool?

Once I have them installed I'll start with lowering the block on piston 2 and 3 first.

[AlekStooge]

These questions are particularly directed toward Cal.

Are the cylinders tapered? Did you fit the rings and measure the ring end gap? I'm guessing you did since you had them on hand.

[AlekStooge]

Ok will do. So are the cylinders tapered?

[DaveBarbier]

Regarding the piston rings, I believe you have, in order from left to right: Oil expander, top ring, second ring, oil rings. Any marks on the rings face up. Usually, the chrome edged ring is the top ring. The oil rings are also chrome edged, but it's easier to tell that they're oil rings because they're thinner and there are two of them.

Would be good to get a confirmation from others before you assemble.

[DaveBarbier]

Also, it's not required to get a ring expander, but rings are hard and therefore, brittle. Too much flexing and they can snap. Also, they can gouge the aluminum piston if you scrape it as you try to get them on.

[AlekStooge]

Was I on point with the staggering of the rings? Don't have the rings at 90 ° of the wrist pin and stagger the rings 120° apart? Again I'm guessing that is only for the top and second ring. Thanks guys.

[DaveBarbier]

It'll say all that in the Clymer or FSM.

[RAFster122s]

I am betting initial break-in it matters more than after break-in. The ring friction being higher I would expect them to not move as much.  But, it is difficult to determine exactly how much...it certainly would be bad to align the slots all in a row.

[AlekStooge]

I'll stagger them like I mentioned, because it won't hurt to do so. If they move they move there is nothing you can do to prevent them from moving. Thanks

[AlekStooge]

I noticed there is a gouge on the skirt of one of my pistons. Is that going to be a problem?



Some of the pistons have some smudges that I tried cleaning with acetone with no luck. Is there anything else that I can use?

[AlekStooge]

Couple questions, when I measure the ring end gap my .006 in feeler gauge (my smallest feeler gauge) barley slides in. My manual says replace if over .028 but does not give a range nor does the manual on the forum. There isn't even anything about the pistons it just cuts off at page 4! Does anyone know the range? I hope I don't have to file the rings.

What is this 4th grove towards the bottom of the piston? I second guessed my self and thought the oil ring expander goes there.

Regarding the piston rings, I believe you have, in order from left to right: Oil expander, top ring, second ring, oil rings. Any marks on the rings face up. Usually, the chrome edged ring is the top ring. The oil rings are also chrome edged, but it's easier to tell that they're oil rings because they're thinner and there are two of them.

Would be good to get a confirmation from others before you assemble.

Dave, by the way the second ring from the left is the second ring because it is thinner than the one in the middle and the 2nd grove on the piston is smaller...so that must be it.

[DaveBarbier]

I noticed there is a gouge on the skirt of one of my pistons. Is that going to be a problem?



Some of the pistons have some smudges that I tried cleaning with acetone with no luck. Is there anything else that I can use?

Not a problem regarding the scratch. Don't bother removing the smudges.

Couple questions, when I measure the ring end gap my .006 in feeler gauge (my smallest feeler gauge) barley slides in. My manual says replace if over .028 but does not give a range nor does the manual on the forum. There isn't even anything about the pistons it just cuts off at page 4! Does anyone know the range? I hope I don't have to file the rings.

What pistons did you get? A lot of them, like mine I got from Dynoman, come with a spec sheet with end gap measurements and such. If you're measuring properly it seems like you'll have to file them down. But would be nice to get an opinion from one of the others. Hopefully I've given you some bad advice somewhere here so Brent will pop in. Seems like when I give bad advice it's like the bat signal for Brent, haha

What is this 4th grove towards the bottom of the piston? I second guessed my self and thought the oil ring expander goes there.

That's the oil groove. Expander and the two oil rings go here.

Dave, by the way the second ring from the left is the second ring because it is thinner than the one in the middle and the 2nd grove on the piston is smaller...so that must be it.

I disagree.

[MRieck]

I noticed there is a gouge on the skirt of one of my pistons. Is that going to be a problem?



Some of the pistons have some smudges that I tried cleaning with acetone with no luck. Is there anything else that I can use?

No

[bwaller]

I think what you're calling a ring groove is actually what a piston manufacturer calls an oil accumulator groove....in your pic the one between the compression ring grooves Not sure what size those pistons are but just use 0.0045" per inch bore for ring end gaps. So for ex. top ring should be 0.010-0.012" minimum, 2nd ring - 0.012" min., oil rails - 0.010" minimum.  Make certain the oil expander ends are butted correctly with no overlap.

Dave, please don't think I'm following you around, and if so it's to see what cool thing you're up to next! More than ever I snoop around here for my entertainment. Race bike is under the microscope for ritual off season rebuild so I have time on my hands!

[DaveBarbier]

I think what you're calling a ring groove is actually what a piston manufacturer calls an oil accumulator groove....in your pic the one between the compression ring grooves Not sure what size those pistons are but just use 0.0045" per inch bore for ring end gaps. So for ex. top ring should be 0.010-0.012" minimum, 2nd ring - 0.012" min., oil rails - 0.010" minimum.  Make certain the oil expander ends are butted correctly with no overlap.

Dave, please don't think I'm following you around, and if so it's to see what cool thing you're up to next! More than ever I snoop around here for my entertainment. Race bike is under the microscope for ritual off season rebuild so I have time on my hands!

Haha, thanks, I'm just playing around I'd prefer you to be looming and ready to drop knowledge at any given moment. Cheers!

[AlekStooge]

Dave and Brent, If I understand you guys correctly nothing goes in the second grove from the top? The oil ring expander and oil rings go in the 4th groove from the top, the one I'm pointing to with the screwdriver.

Race bike is under the microscope for ritual off season rebuild so I have time on my hands!

Well then, you might as well pack an overnight bag and come on down and get to work on a few of the project bikes in my garage, Brent  Idle hands are the Devil's playground and what with Xmas looming, hate to think of you thwarting your own best interests-

Cal, when you measured the ring gap by any chance do you remember what you got? I thought you might have done this when you had the pistons on hand when boring.

[DaveBarbier]

The second groove shouldn't even be able to hold a ring properly.

This should clarify things.

[AlekStooge]

Thanks, Dave that's very helpful.

The ring end gap is almost non existent. Look like I'll have a lot of filing to do. Are you supposed to only file one side?

[AlekStooge]

Cal!  you bored my cylinders for 59mm pistons. You had the pistons on hand. Did you forget? 

Yes they are .50 overbore pistons.

I think I'm just going crazy or I'm missing something/measuring something wrong. Clymer's says replace pistons if the side clearance is 0.007 for top ring and 0.006 for second and bottom. My largest feeler gauge 0.026 feels loose on all of them. I don't know if I have the wrong pistons or what?

[AlekStooge]

Alright, well I trust you more than myself. I measured two inches below from the top like you said, as well as a little bit higher.

[AlekStooge]

That's the .010

[AlekStooge]

I got a Honda manual for myself. It looks like the piston ring end gap should be between 0.005-0.013 Wouldn't it make sense to file less off and increase the longevity of my rings than to file to 0.010-0.012?

How are these tolerances determined, just curious?