Piston problem with my SL750 Polaris Personal Watercraft

I am in the process of replacing my third piston and cylinder on my
1995 Polaris PWC SL750. When I bought I suspect it had this problem.
#3 piston burns a hole in the top after only a short full throttle
run. the problem only happens in the reay piston. I am going on the
assumption that the rear piston and cylinder is running lean and
overheating the piston. I have pressure tested the crankcase for
vacuum leaks and found no leaks. I have rebuilt the rear #3 carburetor
twice and found no fuel restrictions or anything out of place. I have
disassembled and inspected the fuel pump. With no specs regarding
pressure and volume, I can only assume that if it looks good and
functions the way is was designed that it is supplying enough fuel.
Replaced all the fuel lines, removed the inline filter to increase
fuel flow. replaired the fuel pickup to make sure there are no vacuum
leaks.
The most recent piston lasted maybe 4 minutes at full throttle before
failing.
I have set the carburetors to the factory settings.
Is there a problem this I have missed that Polairs PWS have?
Is there something I may have missed?
Is there a way to test the soon to be replacement piston and whatevery
I may try to fix without burning it up? Is there another website that
I may visit to help me sort this out?
any thoughts?
thanks
Howard

I would check the crank index or the rear seal having an air leak.
Come on over to www.greenhulk.net and go to the Polaris section. We
have lots of info and help available there.

On Tue, 18 Sep 2007 18:23:56 -0700, Howard <hcrittenden.DeleteThis@sbcglobal.net>
wrote:

>I am in the process of replacing my third piston and cylinder on my
>1995 Polaris PWC SL750. When I bought I suspect it had this problem.
>#3 piston burns a hole in the top after only a short full throttle
>run. the problem only happens in the reay piston. I am going on the
>assumption that the rear piston and cylinder is running lean and
>overheating the piston. I have pressure tested the crankcase for
>vacuum leaks and found no leaks. I have rebuilt the rear #3 carburetor
>twice and found no fuel restrictions or anything out of place. I have
>disassembled and inspected the fuel pump. With no specs regarding
>pressure and volume, I can only assume that if it looks good and
>functions the way is was designed that it is supplying enough fuel.
>Replaced all the fuel lines, removed the inline filter to increase
>fuel flow. replaired the fuel pickup to make sure there are no vacuum
>leaks.
>The most recent piston lasted maybe 4 minutes at full throttle before
>failing.
>I have set the carburetors to the factory settings.
>Is there a problem this I have missed that Polairs PWS have?
>Is there something I may have missed?
>Is there a way to test the soon to be replacement piston and whatevery
>I may try to fix without burning it up? Is there another website that
>I may visit to help me sort this out?
>any thoughts?
>thanks
>Howard