What size rings?

Hutzpah · Posted: May 13, 2009, 3:12 am Post subject: What size rings?

It shouldn't be long before we in Perth see some rain and as I've been riding the bike through summer I felt it would be a good time to deal with
the excessive oil being used.
As I'm a work from the manual mechanic some advice would be much appreciated.

I measured up last night I think I need 1st over sized rings and pistons
or can I use 1st over sized rings in the standard pistons which are in good shape?

Here's the info I've gather so far-

Pistons 969
left skirt 74.9 right skirt 74.9
left cylinder top ring 1.14 middle ring 0.55
Right cylinder top ring 0.97 middle ring 0.53

What do I do about boring it out as its over the 1mm maximum?
I have but rings in car before but to be honest not sure whats next.

thanks Hutzpah

(1979 xs650 special)

cpotts454 · Posted: May 13, 2009, 7:32 am Post subject: Re: What size rings?

Here are two choices, buy the big bore kit from Mikes XS, or buy a new jug from ebay and bore. I am not sure about boring over 1mm so thats the only two options I know of.

yamaman · Posted: May 13, 2009, 8:04 am Post subject: Re: What size rings?

Hutzpah wrote:

What do I do about boring it out as its over the 1mm maximum?

(1979 xs650 special)

How do you figure that? To detimine what/if rebore is needed (if there is no scoring ect), you need to take the cyls to a machinist & have him measure the bore & pistons for you.

Ray Easson in Bayswater is very good at this! You could also take him your head while your at it & he might even look at that for you!

Cheers

Retiredgentleman · Posted: May 13, 2009, 11:28 am Post subject: Re: What size rings?

The Yamaha service manual at www.biker.net gives the specs for cylinders, pistons, valves, valve guides etc.

Hutzpah · Posted: May 14, 2009, 4:45 am Post subject: Re: What size rings?

Sorry about the confusion what I meant by

"What do I do about boring it out as its over the 1mm maximum?"

was the ring gap is over 1mm max on standard rings.
Anyway I went to a local bike shop near work and they sent me to a machinist(as yamaman said)
For a $150 dollars he can bore and hone to take 0.25mm oversize rings but will need the over sized pistons when he does it.

Thanks for your posts
The picture is starting to get clearer.

Hutzpah

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Yamaha xs650