Well, the problem is that I think I have a broken ring on my AC 454.It smokes a little bit when first starting and Has some blow by around the plug. There is a small weep hole on the left side of the head ,suposed to be to drain water out from area around spark plug, mine is oily. Does this sound like brpoken ring? Also will a 500cc piston fit if I bore mine out or do I have to replace head ? Mine still runs great and has plenty of power.Thanks
Keith
98 AC 454 4x4 2000lb Warn
http://photos.yahoo.com/keith_rndmt

 

If you are getting a little smoke only at start up the problem is more likely a valve seal or valve guide problem. If it is a broken ring you would have a drop in compression and a probable loss of some power. A compression test could verify this. As far as the oil in the plug hole I would have to speculate that it is coming from above (maybe the valve cover gasket or o-ring)and running down into the plug area.
If you should find that you have a broken ring and decide to replace the piston I would stick with the first oversize of the stock piston that the cylinder will clean up at.
Oversizing a cylinder any more than necessary results in a loss of reliability due to increased inabilty to disipate heat. This is more of a concern with a utility quad than a sport quad because of the heavy work situations they are put in.

 

Trailboss is right, If you lost a ring you would loose all of you compression. And it does sound like a valve guide. You can drop a bigger piston in. Its the same block as the 500, SO I wouldnt worry
matty

 

Yea, just order a sleeve and piston from a 500 and have the sleeve pressed in after you rebore the jug.