sparks timing key Qs and confusion

[bry14661]

ok so i have my motor apart right now replacing a valve guide seal that was pouring oil into my motor. Well im going high compression with a new piston and a stage 1 or 2 cam. plus i have the 450r carb. will it be safe still to do a sparks timing key. From what ive herd it makes the motor run as if its higher compression. Would i be to high of compression with both and start blowing gaskets? any proven info would be awesome.

[tri5ron]

as long as your new piston is BELOW a 12:1, and you stay 426 or less, the sparks key will work fine.

Compression, or bore, any higher than that, is not recommended to use the advance key.

here's a link to my pictorial installation....

http://www.exriders.com/vbb/showthread.php?s=&threadid=349499&highlight=sparks

[drew416ex]

How come sparks says anything over stock compression will make too much heat with the key? I thought of putting it in mine but sparks says not to.