[echo80]

Hi,
I've been working on my 78 CB400T2 and recently had the valves re-seated and cylinders honed. I got the pistons all cleaned up and as I was putting the new piston rings on, one of them broke. It was the middle ring. For now, I used the old piston ring as a substitute, as it was still within the specification threshold. I haven't put everything back together yet, so before I do I want to get a sense if it's okay using one old ring, or if all my work will be for nothing if I do this. I know ideally I would order new rings (again) since all the other rings are new and the pistons are freshly honed. But what happens if I don't take the ideal route?

Thanks

 

[apdaniel]

I could not live with myself always wondering one way or the other. So I would order new and know I have a fresh ring to seat.

 

[J-T]

Using the old ring will not cause a catastrophic failure (well, probably won't anyway).

Cost of rings verses peace of mind.

 

[blu3fan]

not worth it. buy new rings.

 

[dtsmjr8dan]

+1 on new rings for that piston. After all the $$$ you've already laid out to get to this point, get a new set and ride knowing it's ALL done right.

 

[echo80]

I let the frustration settle, went to bed, and woke up with better intentions. You're all right. I've ordered another set of piston rings to finish the job properly. Thanks.

 

[DD23]

Is the engine in the frame?

If not, is the engine assembled, with just the cylinder and head to refit?

You are aware of the con rod oil hole and its relationship with the piston, as well as the big end cap bearing notch locations?

You are also aware of the ring "marks" , spacings and the 3 piece oil control ring fitment, the "expander" butts up against its ends.

From memory a 400 con rod will pass thru the cyl bore.

For a total engine reassembly job, I fit the prepared piston and rods into the cylinders, via the taper, on the "bench" , and offer the "unit" to the upper c/case, with gaskets etc, and hold in place with some spare main bearing casting bolts ( 2 are sufficient, one outer front and one outer rear ) so I don't run the risk of ring breakage when fitting the cylinders to the pistons. The crank can then be fitted, b/end caps and balance chain/slipper etc. with ease, and finally the main bearings and casting etc.

I use ring clamps ( rigid plastic pipe with a slit ) for easy piston fitting when engine in situ. There is a generous "taper" at the cyl bore mouth but trying to align 2 pistons and rings at the same time single handed can be "tense".