1996 Magnum 425, Leak Down Test Fail

[bkhall]

Hi all,

I bought this ATV not running, and while doing the leak down test found air leaking from a hole above the exhaust port on the cylinder head. Does anyone know what this hole is connected to? I have a repair manual, but it does not state anything about it. Could it be a part of the auto compression release mechanism? Any help would be much appreciated.

Thanks.

[GEARHEAD01]

i would phone ask a polaris mechanic but it seems like you are on the right track.

[bkhall]

I went ahead and started taking the head apart yesterday and found that the hole is a drain for the spark plug recess. I pulled the cam and found the exhaust lobe to be gone. I think my leaking was the rings. Time to put some money into it. Thanks for the reply.

[DirtDemon]

If the air was escaping through the spark recess plug drain hole, then it seems to me that you were losing air past the spark plug, why elso would air be leaking out of that hole? I'm not trying to say that you aren't losing pressure past the rings, I am just pointing out that there is something else to look at here. Could have just been that the plug wasn't tight, but you may want to make sure the spark plug threads aren't damaged.

[bkhall]

I don't think the spark plug adapter was tight, I am not sure how the air was going out the drain hole. I was plugging everthing I could to find where I was losing pressure. In the end I was definetly losing air past the rings.