1st oversize piston ring question

**Crazcnuk** · 05-25-2009, 11:52 AM

I just put 1st over in my 80G engine (probably the other post you read).

Unfortunately, I haven't finished it yet, so don't know how well it will work.

I used 1st over compression rings, and had to file them to get the proper (minimum) gap. Just follow the procedure in the manual. I used a bench grinder (very carefully) to 'file' the rings, then used a flat file to remove any rough edges.

I couldn't use the 1st over oil rings (as someone suggested in the other thread) because the radius they are made for is too large, ie the expander holds the rails out too far.

So I used the old oil rings and they were still very snug.

I went with 1st over because, before honing, a NEW standard top compression ring was at the maximum factory gap. (Not the max service limit) With the 1st over rings I could put them at the minimum(ish) factory assembly gap.

I am also lapping the valves, and putting in new viton valve seals, new gaskets and a new cam chain.

The funny part is the piston to wall clearances, etc. were all within spec, albeit on the loose side.

**TopCatGr58** · 05-25-2009, 03:34 PM

Hey JF,

There was a recent thread, might have been the one CrazCnuk posted, but a search for Piston Rings should reveal it. There was a reference of a company that sells generic piston rings, but "we" didn't know what the width of the actual ring was, as well as it's height, so try to match it up with ones that they offer. Since you have your rings out, if you have a micrometer you could measure the rings and figure out what size would be a match for the stock sizes that they offer, and get them a bit cheaper than Yamaha OEM!!
T.C.

PS, would you mind posting your measurements for the rings, so others could possibly benefit from a possible source of cheaper OEM sized rings?

**jfmerk** · 05-25-2009, 05:25 PM

TC,
I found the thread your speaking of and I'll post my piston ring dimensions there. I am not real sure about how to measure the oil control ring but I'll attempt to measure it as if it were "in the groove", and I'll need to borrow a caliper with ground ends to measure the groove diameters of the piston.

**Shappers** · 05-25-2009, 11:56 PM

It is quite normal to do as you suggest, if the original pistons and bore still measure within specifications then it is OK to fit 1st oversize rings with the end gaps filed down to the correct end gap.

I thought that original sized rings are impossible to come by now whereas 1st oversize ring sets do appear on ebay from time to time. I paid only $35 for the last complete set (pattern rings).

**Crazcnuk** · 05-26-2009, 01:32 AM

The 'new' rings I got were not chamfered at all. They are just square. I installed them with the markings 'up' as per the manual.

**TADracer** · 05-26-2009, 06:35 AM

Unless I missed something, why are your original rings no longer useable? Is it the end gap?

If one is bent or broken it would probably show up on your cylinder walls or on your piston as streaks and scoreing or on your piston as excessive ring groove wear. But your machinist says your pistons and cylinders are OK which makes me think it would only be wear that makes him recommend new rings. So, did YOU measure the gap or are you relying on what your machinist told you?

True, the rings are the intended wear part of the piston/cylinder combination. If it is just the ring gap and you are still within a MM or two of the factory range then I dont know if I would spend the $ for new rings for a street motor. Reason I say this is that over the years I have done a deglaze hone twice and then remeasured the cylinder in several places. A light honing removes no measurable material. I reused the original rings both times even though the ring gap was on the wide end of the range. My compression is very good, I do not burn any oil and my piston/cylinder wall cearances are still within factory spec.

**Crazcnuk** · 05-26-2009, 11:36 AM

You mean like mine where the gap, on the compression rings, was over .084" ?

**jfmerk** · 05-26-2009, 06:18 PM

Originally posted by TADracer

Unless I missed something, why are your original rings no longer useable? Is it the end gap?

If one is bent or broken it would probably show up on your cylinder walls or on your piston as streaks and scoreing or on your piston as excessive ring groove wear. But your machinist says your pistons and cylinders are OK which makes me think it would only be wear that makes him recommend new rings. So, did YOU measure the gap or are you relying on what your machinist told you?

True, the rings are the intended wear part of the piston/cylinder combination. If it is just the ring gap and you are still within a MM or two of the factory range then I dont know if I would spend the $ for new rings for a street motor. Reason I say this is that over the years I have done a deglaze hone twice and then remeasured the cylinder in several places. A light honing removes no measurable material. I reused the original rings both times even though the ring gap was on the wide end of the range. My compression is very good, I do not burn any oil and my piston/cylinder wall cearances are still within factory spec.

I didn't quite give all of the information

You see, being that this is my first motorcycle restoration (I restored a '83 Venture but this was mostly cosmetic repairs) with a complete engine overhaul, I didn't extend a great deal of care trying to dig out the rings from the piston grooves. I thought I'll be replacing them anyway... without researching their cost or availability! Lesson learned! These rings where seriously packed in with what I believe was hard burnt oil / carbon. In the process of digging them out, several broke but I do have one good set that have a gap measurement within the range. I posted the ring dimensions on another thread. The cylinder bores all measure 2.815"~2.816" with very clean cylinder walls. Oh and the broken rings made a great tool to clean the grooves out!

Does anyone know how the first and second rings are constructed? To me they look like cast iron with a chrome OD? True???

**TADracer** · 05-27-2009, 06:58 AM

Originally posted by Crazcnuk

You mean like mine where the gap, on the compression rings, was over .084" ?

Sorry, I meant a .mm or two in my writing, not a MM or two. And yes, .084 is a bit much, IMHO. I dont have my book in front of me but isn't the ring gap spec on the two compressions something like .2 to .4 mm or about .008" to .015". .084 is a bit wide, I would think.

1st Oversize rings should be good to use with some gap filing. But the point of my comment is that for a street machine, even if your ring gap is a bit wider than the service specifications (a 'bit' being defined as a couple of thousandths) you should still get good performance and it might not be worth the high dollars to replace a set of rings like that.

**Shappers** · 05-27-2009, 11:53 PM

The pattern rings that I have are just as you describe, two-tone with a chrome outer ring. The original Yamaha ring set that I have are all one colour.

**Crazcnuk** · 05-28-2009, 12:02 AM

The ones I took out looked like cast iron top ring with a Chrome/Moly 2nd ring.

The new ones are hard to say, but they were all the same color.

**randy** · 05-28-2009, 02:27 PM

NOS 1st oversize rings on E-bay

If you really want original oversize rings, they are on Ebay right now!

Item # 200347162428

**Crazcnuk** · 06-01-2009, 03:25 AM

Fired the rebuild up today, purrs like it should.

Discovered I have a major valve cover leak and my silicone tensioner gasket didn't work... but it runs nicely, so far.

1st oversize piston ring question

1st oversize piston ring question

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