1972 CB350K Piston Rings

[Honda55]

I've been on and off working on rebuilding a 1972 CB350K motor. Just got the motor shell and pistons back from being cleaned and vapour blasted. Will have to replace the exhaust valves (unexpected) and piston rings (expected). I've ordered the piston rings, asking for standard rings (ie 64mm - 3pc oil rings, 2nd ring, and top ring), which I believe are spec for my Honda model.

While waiting for delivery, I removed the existing rings from one piston and discovered that the oil ring is a double layer ring with holes (see photo below) that looks nothing like those I've seen in pictures, and nothing like the ones I've ordered. There's no putting the ring back since it broke on removal.

I'm puzzled: did I order the wrong ones or were the wrongs ones put on my pistons by the previous owner or are the ones I ordered and the ones on my pistons interchangeable, i.e., one is OE and the other isn't? Suggestions and comments welcome.

 

[66Sprint]

The slotted one piece original oil rings are much more expensive to manufacture, so the three piece oil rings now commonly replace them......
Use what you get/have and they'll work fine if installed correctly.....Make sure the middle "expander" section butt joins rather than overlaps, and stagger the gaps in the "flat" top and bottom section rings away from the butt joint.......

 

[Honda55]

Thanks for this 66Sprint. I was getting confused. But I guess that's to be expected given an almost 50-year-old bike with numerous owners and an amateur mechanic. But I didn't know that the expander section "butt ends" rather than overlaps. Is there a formula for ensuring correct positioning and staggering of the gaps? When I get to that point, I'll search for piston ring installation videos as I'm sure there's a standard installation technique. FYI - I had considered over-boring the pistons, thinking it would give me a bit more power. But I was advised against that since the extra power would not be noticeable or worth the cost. So, I'll leave it as is and simply install the rings once they arrive. Again, thanks.

 

[ancientdad]

...I'll search for piston ring installation videos as I'm sure there's a standard installation technique.

Please do not search for a video, the first one you find will likely be a "common" place that misrepresents themselves as being experts. Ask here, it isn't a big deal, you just have to use caution. When I put rings on pistons, I go one ring land at a time (with the exception of the expander portion of the oil ring set, since it's very flexible). Many people try to put the second ring into the second land, or groove in the piston, immediately and sometimes break the second ring as a result. They are a bit brittle and need to be handled with caution, only expanded just enough to get them into a land, and then moved to the next land in the same manner. As for spacing, with the 3 piece oil ring set you'll have 2 more gaps to space (the center section "gap" is immaterial on the oil ring). Here's a decent guide. Note that you never want any gap on the forward, or thrust, side of the piston.

 

[Honda55]

This sounds like a good technique. And thanks for the pic on positioning the rings. I understand that the rings themselves, with the exception of the expanding oil ring, have an upside and downside. But which is which? I expect the receive the new rings today. I'll look to see if the sides are marked. Cheers.

 

[Ribrickulous]

Please do not search for a video, the first one you find will likely be a "common" place that misrepresents themselves as being experts.

We really need a bot on this thread that scans for the word “Video” in the comment and immediately responds with a picture of AD scowling... I feel like it could save him a lot of time [emoji14]

The top two piston rings have lettering/numbering/markings on them. When you see them, that is the “top” side. I believe there’s a chamfer on the top as well, but the markings are the sure indicator.


Ed
1972 Honda CL350

 

[Honda55]

I'll try to never ever use that word, though I'm sure to forget. Will look for the markings and the chamfer. Later.

 

[ancientdad]

We really need a bot on this thread that scans for the word “Video” in the comment and immediately responds with a picture of AD scowling... I feel like it could save him a lot of time

LOL... it really doesn't create angst for me, but it does cause discouragement when I think of the thousands of people who watch their videos daily and go right out to the garage and get their drill to lap their valves, their chisel to pull the cam bearings before even rotating the cams to a point where there's no valves open, and to throw their feeler gauges in the trash for setting points and just ignore the most basic aspects of mechanical knowledge that so many of us learned when we were young and starting out while listening to real mechanics who actually understood how engines work (and NOT to someone who somehow acquired the nickname "Honda Wizard" while instructing all of those bad habits to unsuspecting noobs).

 

[LongDistanceRider]

Pick the one you want to use

 

[ancientdad]

Obviously, the third one seems the most impressive... "I always wanted to work on a transmission boss..." while he plays with the spray nozzle on the garden hose (old AAMCO commercial)

Wait - I didn't see the one that says "Honda Wizard"

 

[DoctorRuckus]

There's no shame in a cheap pair of piston ring pliers.

[SUP]
Please don't ban me from the forum.[/SUP]

 

[Honda55]

There's no shame in a cheap pair of piston ring pliers.

[SUP]
Please don't ban me from the forum.[/SUP]

No shame indeed. Whatever gets the job done. Got the rings on.

Now, if I could only figure out the shift drum positioning. If it isn't one thing, it's another.