06-18-2011, 11:42 PM #1
96 GTX Seized the PTO piston WHY is the big question ?
The ski is bone stock.
Complete engine rebuild with rebuilt crank and counterbalancer shaft, bored with new ProX pistons and OEM gasket kit, .055 squish. Fuel tank removed and cleaned, pickup screen cleaned, new fuel lines, separator cleaned, carbs rebuilt with Mikuni kits.
First ride about 2 hours no problems and I ran some oil premixed with the first tank of fuel. Second ride about 1.5 hours with some full throttle for a few seconds heading back to the ramp at about 3/4 throttle it died. Fired right up then died a few seconds later.
After tear down the PTO piston had seized. The only reason I could find is the manual calls for the high speed screws to be closed on the MAG and 1/2 open on the PTO, I had them both closed. I can fix the damage where do I go to find the cause ? Would the closed high speed screw do this ?
I'll post some pics tomorrow when the jugs come off.
06-18-2011, 11:51 PM #2
The Infamous "lean" 3/4 throttle phomeonon strikes again..
06-19-2011, 12:10 AM #3
06-19-2011, 12:17 AM #4
i dont know,i've read and heard of this for years,Theres and article on SEA-DOO.net site.PPG performance talks of it.
06-19-2011, 02:31 PM #5
06-20-2011, 08:50 PM #6
Oil pump has been tested and works fine, using Amsoil Interceptor.
Carbs have been apart again and are spotless nothing in the filters and the pop off is 28 psi on both carbs.
Looking at the jetting specs and settings in the manual the 96 specs show both HS screws closed and the 97 specs show closed on the mag and 1/2 open on the PTO. Interesting since the 96 and 97 are mechanically identical machines. I'm going with 1/2 on the mag and 3/4 on the pto as I would rather be fat and happy rather than sticking pistons every second ride. After a few tanks I can do some plug chops and slowly close the highs.
Engine will get pressure tested once assembled.
Any other advise or input much appreciated.
06-21-2011, 07:04 AM #7
- Join Date
- Sep 2008
Doesn't look like it was getting much oil. What do the tops of the pistons look like? Plug color? Compression before it seized?
06-21-2011, 01:26 PM #8
Right is MAG
The PTO cylinder had more residual oil in it than the Mag cylinder.
Sorry no pics of the piston tops as they are already at the machine shop. The MAG piston had a normal looking brown wash on top the PTO piston was black and oily.
No compression numbers, it only had 3 1/2 to 4 hours run time on new ProX pistons.
06-21-2011, 03:43 PM #9
- Join Date
- Sep 2008
Were the carb filters cleaned?
06-21-2011, 04:13 PM #10
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