Another piston ring question

[webbie]

Hi all, I know from a forum search that piston rings are the source of some confusion - e.g. installation order, the fit of various brands, etc.

I'm rebuilding my '82 with a set of Cruzinimage pistons, 447 type, 1mm oversize.

I understand that stock rings will be stamped with "R##" to differentiate the compression and wiper rings. I also understand that the compression and wiper rings are different thicknesses, and should only fit in the correct order.

However, that's not the case with these. The two thickest rings are stamped with "STD," and appear to have identical thicknesses - both rings fit into both grooves, regardless of the order (see pics).

The rings are differentiated on the following base:
Ring #1: Silver (chrome) finish on the outer edge. Beveled on the outer edge.
Ring #2: All black. Appears to have a perfectly rectangular cross section.

From what I've learned, I THINK the chrome-plated + beveled ring is the top compression ring, but I wanted to make sure I'm not off-base. Can anybody confirm the installation order for the rings that ship with the Cruzinimage pistons?



Stamped with "STD"


Chrome plated on left, black finish (cast iron?) on right


Rings fit in grooves in either order

 

[B Burdine97]

Alot of people have been having confusion with cruzinimage's piston kits and which ring goes where, including myself. On the stock yamaha Pistons the top compression ring is 1.2mm thick and the bottom compression ring is 1.5mm thick. The rings that come in cruzinimage's piston kits are both 1.5mm thick, and he includes no instructions as to which compression ring goes where. The top compression ring is the silver edged one, and the next compression ring is the black edged one. I will attach a photo of cruzinimages direct response after I emailed him asking which ring goes where. The English isn't the best... Haha. But you get the point. I was going to start a thread describing all of this for other peoples future reference, but I guess it'll be in this thread.

 

[B Burdine97]

Here is the email from cruzinimage.

 

[5twins]

That matches up with what the shop manual says. The top ring has the chrome plated edge so it's more heat resistant. The second ring is cast iron .....

 

[webbie]

Yep, that's what I thought. The chrome finish was the clue for me. However, the lack of a lip/ledge on the wiper ring threw me off a bit.

Thanks!

 

[5twins]

One more thing - here's a Yamaha tech bulletin showing the recommended end gap spacing .....

 

[B Burdine97]

There are so many different orientations for 4 stroke piston ring end gap positions. I used this one, straight out of the manual. Worked just fine.

 

[5twins]

Yes, there are many different recommendations. Basically, you just need to space them so they're not in line and not place any over the piston pin. This is for the initial start-up mostly because once you're running the engine, the rings will slowly move around.

 

[webbie]

Excellent info, thanks all.

Unfortunately, I screwed up the ring installation and broke a ring...

I messaged Mitsuo through ebay to see if he sells replacement rings for his pistons. I'm my own worst enemy on this rebuild.

 

[B Burdine97]

Damn! Im sorry to hear about that man. Im sure he will sell replacement rings for cheap, the shipping is what will get you though. The use of a piston ring expander pliers helps to ensure that you wont break them. Good luck sir!

 

[TLCbobber]

Alot of people have been having confusion with cruzinimage's piston kits and which ring goes where, including myself. On the stock yamaha Pistons the top compression ring is 1.2mm thick and the bottom compression ring is 1.5mm thick. The rings that come in cruzinimage's piston kits are both 1.5mm thick, and he includes no instructions as to which compression ring goes where. The top compression ring is the silver edged one, and the next compression ring is the black edged one. I will attach a photo of cruzinimages direct response after I emailed him asking which ring goes where. The English isn't the best... Haha. But you get the point. I was going to start a thread describing all of this for other peoples future reference, but I guess it'll be in this thread.

found this thread whilst looking up end gap for my new pistons and rings. as it happens I've also bought from cruzinimage in Japan, but my experience has been very good. bought 78mm pistons and the rings are as you would expect and quite easy to identify which goes where, thinner top ring, thicker bottom ring... they'll only go one way... two if you count upside down but the marking will avoid that. the search for end gap numbers continues.

 

[TwoManyXS1Bs]

... the search for end gap numbers continues...

http://www.xs650.com/threads/where-did-it-go-im-am-worried.48861/page-4#post-498445

 

[TLCbobber]

http://www.xs650.com/threads/where-did-it-go-im-am-worried.48861/page-4#post-498445

Thanks 2M, I sent cruzinimage a message asking for recommendations on ring end gap since it was remarked elsewhere that end gap should be determined by ring manufacturer...
Here's the reply:
Thank you for your message. regarding clearance.
I asked my supplier about clearance.the clearance is 0.035-0.045mm
and regarding other measurement. my supplier have not detail of specification.
So, They can't confirm how many size.
sorry.
Best regards,
mitsuo

accounting for language barrier I'm assuming 0.035 - 0.045mm refers to piston/cylinder clearance as it equates to 0.00137 - 0.00177" which wouldn't be enough for end gap.

Thanks for the link, trying to filter out what I need.

 

[Paul Sutton]

I just looked back at Entry 1: It refers to 1mm oversize pistons with rings marked "STD". Seems very unusual! My pistons from Cruzinimage were 0.50mm oversize and the rings were marked "50". I used the Yamaha recommended end gaps for all rings. The only bit I did not like about the pistons were the very thin circlips. The stock Yamaha circlips were thicker.

 

[xjwmx]

The use of a piston ring expander pliers helps to ensure that you wont break them. Good luck sir!

It does, but you can do the same thing as the pliers with your fingers just as effectively. Put your thumbnails in the gap, and steady the ring with your forefingers and expand it the same way the pliers do, just enough to slip it over the piston. They're so brittle I wouldn't try it any other way.

 

[xjwmx]

The rings I got from cruzinimage were different from what you guys are describing. The top and middle rings were identical; same thickness, same profile, apparently same material, and no markings. Simplifies things quite a bit

 

[IllusiveJack]

I have a question, the compression ring has the chrome plating and the scraper ring is just one shade of black, when I look at the ring ends with a watchmakers eyeglass, the scraper ring has beveled edges the same as the compression ring, what's odd is I have another set of 1.0 oversize and the black ring has the correct shape to scrape! Looks like I got some weird scraper rings?

I just read another post about old and new rings and seems the new scraper rings have beveled edges :/

 

[TwoManyXS1Bs]

Yup, the "scraper" edge of the 2nd ring was removed around 1973-1974. Doesn't seem to be an issue...