Oversize piston rings

[chuck hahn]

So ive got to take the top end off the burgundy 1000C at some point to see why it has started to smoke rather heavily. So in anticipation of possibly some bore damage i was looking at the service manual. It says oversize rings are in two sizes. .5 and 1 over. Seeing ive not yet had to have a set of cylinders bored, my question is do they just bore them and i put oversize rings on the stock pistons or do i need oversize pistons too?

 

[GregT]

Pistons and rings. There's a good chance that the rings aren;t too bad - but the ring grooves wear. Excessive side clearance will make smoke.

Many possible reasons for smoking as you know. Valve stem seals are the point to start looking.

 

[Suzukian]

As stated, look at the valve stems first. Re ringing works, but you have to take the cylinder head off, or at least the head, and have a good look at the cross hatching to see if they are worn smooth. Personally, If I was going through all that trouble, I'd buy a set of 1st over pistons with rings, refresh the cylinder head (new stem seals, valve guides, polish valves with rouge) and you will have essentially a new motor that you won't have to mess with a long time. You will have to replace the gaskets to check everything anyways, your major expensive will be buying the pistons bored and honed by a shop.

Start at the valve stems first though. They can shoot out a lot of oil when bad. It could save you a lot of money.

 

[zed1015]

If the bores are just glazed and a hone leaves the piston/bore clearance within spec you would re-use your pistons and just fit new rings of the same size.
If the bores are worn and the clearance too wide to take a hone you would need a rebore and fit new pistons and rings of the next available oversize.
Chances are though that the recent smoking is due to worn valve stem seals and possibly guides.

 

[rphillips]

Stock pistons use stock rings, 0.5 over rings go on 0.5 over pistons. etc

 

[uk gs nut]

My GS1000 had a smoke and oil burn problem. I fitted viton stem seals using the rope trick down plug hole. Seems to of done the trick, I've not had to top oil up in 1000 miles. It would have been on lowest mark before seals fitted.

 

[bwringer]

Yup, you need the matching OS pistons.

Availability can be a problem; it has become very difficult to order these parts from Suzuki. Cruznimage has OS sets, though.

 

[Suzukian]

No matter what you end up doing, you do have to check the end gap on the rings.