Replace piston rings?

[Johnny K]

82' 850GZ. I have a project coming up when I get garage space that a friend/mechanic is going to let me use. I am going to replace the valve, head and base gaskets. I have the vesrah gasket kit. I was just wondering if I should order piston rings where as I will be able to replace them if need be. Any suggestions and places/websites that people have bought them from. Thanks again. -John-.

[mark]

How many miles on your bike?

If I was doing this, I would wait to order new rings until you have your motor apart and the cylinders have been inspected and measured for proper clearance. If the cylinders are out of spec. you might want to go with a re-bore and oversized pistons in which case your stock rings wouldn't work.

It seems to me you're on the right track though with new rings. Even if everything is within spec. new rings and a cylinder honing seems basic as long as you have it all apart.

I like to order my stuff here, because you talk with people who know what they are talking about. http://www.z1enterprises.com/

[chef1366]

Don't you use the oversized rings in the stock pistons?

[Nessism]

Don't you use the oversized rings in the stock pistons?

Oversized rings go on oversized pistons and require a bore job. There are some exception to this rule in the old time automotive world but not for motorcycles.

[mark]

Don't you use the oversized rings in the stock pistons?

I don't get what you mean. Are you saying that the rings for both stock and oversized pistons are the same? Maybe I'm wrong, I assumed they were different.......maybe I'm misunderstanding what you're asking.

My oversized pistons and rings were sold as a set with a single part number, so it would be hard for me to check.

[rphillips]

The stock pistons use stock rings. The oversized pistons use oversized rings. Figure this way. If your pistons are 2mm larger than stock pistons, Your rings will be 2mm larger than the stock rings

[rphillips]

Oh yeah, I forgot. While it's apart, Replacing 25 yr old valve seals & lapping the valves probably wouldn't hurt a thing. Some will not like lapping valves, but surely nobody would disagree on the seals.

[Johnny K]

I have 22K on my bike Mark. So the consensus is order new rings?? How do you "lap" a valve?

[mark]

I think the consensus would be to put in new rings and hone the cylinders as long as your bores are within specification. But again, I think I would wait until you check your cylinders before you order the rings.....if you need to go oversized pistons, then you'll need oversized rings.

In other words, rings are a great idea, but check your bores first before ordering them.

Valve lapping? I've never done it....when I rebuilt my head, I just had the valves and valve seats taken care of at a machine shop. What it is, is taking each valve with a little valve grinding compound and spinning (lapping) the valve in the valve seat.

Here's a thread arguing the pros and cons.

http://www.thegsresources.com/_forum/showthread.php?t=84587&highlight=%22valve+lapping%22

[chef1366]

I was asking because I did not know. I've only gone from 72mm to 75mm so there was a change in the piston size no doubt. In my line of thinking the ring inner diameter was the same but the surface was larger since we are only talking about .5mm. I'm not always the sharpest tool in the shed. ;-)

[Johnny K]

Thanks for that thread about lapping. A little over my head but its okay. Probably a smart move to wait and see if I need rings or not.