I have a set of 4.065 cp pistons ,the instructions with the pistons say to gap the top compression ring at bore x .005 and the 2nd compression ring at bore x .006 this is for motorcycles and atv's,this seems a little excessive to me was wondering what the engine builders on this site are gapping there cp pistons at? and also what the negative if any conseqences of excessive ring gap are.

 

The negative of excessive ring end-gap is far less damaging than the negative of not enough end gap.....

.005 x 4.065 doesn't sound like too much to me.

 

The negative of excessive ring end-gap is far less damaging than the negative of not enough end gap.....

.005 x 4.065 doesn't sound like too much to me.

 

anyone else

 

that sounds right to me.

I did my C/Ps at 18 and 20 on my 95 ci.

 

OK thanks for the replies ,I just thought that maybe the piston manufacturers might put this spec. in there instructions to be on the safe side and avoid customer complaints if rings are gapped to narrow resulting in piston failure ,so I thought I would throw it out there and see what others have gapped there rings at,because I didn't want to have an oil burner when I put it back together,so yes I guess I shouldn't be trying to re invent the wheel and go by the instructions that came with the product they know it best.

 

Most customers aren't DIYers. They are actual trained professionals, who know what they are doing.

 

no doubt in my mind,thanks for the help.

 

CDN. RG: The gaps are norm for these kind of aircooled setups. Ever wonder why the second ring has more gap than the top. Well, I did and found this expanation that I thought I'd pass along to those interested.

Thinking on piston ring gaps has also changed. In the old days, second ring gap specs were tighter than those for top rings because they didn’t see as much heat. But this didn’t account for inter-ring gas-pressure buildup between the top and second rings. If the pressure between these rings equals or exceeds the pressure above the top ring, it can cause the top ring to lift off the bottom of the piston ring groove and lose contact with the sealing surfaces. It also inhibits the ring’s ability to transfer heat from the piston. To keep inter-ring pressure from becoming a problem, the current trend is to create an easy escape path for the built-up pressure by gapping the second ring larger than the top ring. Another benefit is that because gas pressure is now directed downward towards the sump, any oil that has collected in the ring pack areas will go with it.
Ron

 

Thanks for the explanation Ron very informative.