Thread: slt750 #3 piston deto.
10-16-2009, 10:07 PM #1
slt750 #3 piston deto.
New to the polaris brand ,but not to pwc have a couple kawis, any way I have been able to access great Info & resources. this slt w/#3 piston Deto. Ive done a leakdown held just fine, going two sizes up on the main jet & installing restrictor. former owner had low speed screwed all the way in,funny thing is the motor & gaskets look almost new,as if someone was in there recently! Im going to reassemble very carefully & hopefully I can cure the problem hoping to make this a dependable boat for wife. Thanks to all. & could someone explain what the fuji motor is compared to all others. Thanks Again Brian
10-16-2009, 10:23 PM #2
There are a few updates that are recommended for this ski. The gas cap cracks and is a possible source of trouble, fuel lines deteriorate in the tank. check them.! and it's recommended to upgrade to a mikni triple outlet pump, axe the auto-cock. and change all the fuel lines. And rebuild the carbs if it's been sitting for a while. keep the restrictor in the return line if changing lines, it's about 1/2 inch from the return line off the carbs with a black tie-wrap around it. It's a small brass insert for fuel pressure.
It's a fun ski to own I have one myself. Let others chime in on this subject. They all know far more where to point ya than myself. Read some of the tech tips and how to's in here. There great and very informative.
10-16-2009, 10:28 PM #3
- Join Date
- Jul 2007
- near Toronto, Canada
Are you sure the PTO piston (#3) was damaged by detonation?
What model year is your SLT 750?
If the original fuel and oil lines are still in there, now would be a good time to replace them all, including any found inside the fuel tank.
Not sure what you mean by explain the Fuji motor
For the first few model years, starting in 1992-1995, Polaris contracted with Fuji Heavy Industries to provide engines for the newly formed Polaris watercraft division.
First year was only the blue painted 650cc model, 1993 saw the 750cc introduced. The largest 'regular' Fuji was the 780cc (1995-97), and starting in 1997 the race tuned Pro 785 version.
In 1996, Polaris began using their own 'domestic' red engine design, and quickly phased out the Fuji engines, but the Pro 785 was sold until 2000.
Have you seen this link?
Polaris Fuji (blue) engine
10-16-2009, 10:50 PM #4
The hole in the piston,looks like a lean cond or deto. As far as oil & gas still in boat was pumped out,Im going from the fuel tank to carbs R$R
what is needed, like I said slow & methodical, I want a reliable boat fpr wife. As far as fuji you answered my question Thank You
Last edited by blegan; 10-16-2009 at 10:58 PM. Reason: insuffiecent
10-16-2009, 11:07 PM #5
- Join Date
- Jul 2007
- near Toronto, Canada
Usually caused by clogged carbs, weak fuel pump, old and failing fuel lines, aged fuel selector valve, or missing fuel return line flow restrictor (if you model had one).
If your engine still has the small auto-cock device mounted near the fuel pump, delete it, and cap off the vacuum port at the carbs.
Another possible cause for lean operation is a leaky crank shaft seal at the PTO shaft. Examine the seal carefully for signs of damage or wear.
When the engine is back to running condition, you can monitor the piston wash for signs of lean, and/or use ether engine starting spray to identify a leaking seal or gasket.
Be sure to rebuild the carbs with genuine Mikuni parts, and go through the rest of the fuel system thoroughly.
A common upgrade is to install anew three outlet Mikuni fuel pump, which ensures sufficient fuel flow, even as the pump ages.
Were the carb needles damaged by the previous owner tightening them too far in?
If you rebuild the carbs and fuel system properly, there should be no need to change the carb jetting.
Use the correct spark plus, and trim the ends of the ignition wires a little to ensure solid wire to cap connections.
10-17-2009, 11:06 AM #6
The restrictor should had been inside the return line already. Not there huh? Replace the one way air check valve at the fuel tank also. They wear out by not holding pressure and by clogging up. Clogging up will cause a lean condition too. Your boat has the fuel pump high at carb rail rack. Replace the fuel pump with the Mikuni 3 outlet pump and run a line to each carburetor fuel inlet and relocate the fuel pump so that it is low inside the right hand hull close to the engine block pulse line fitting. The pulse line needs to be as short as possible but the fuel pump needs to be just higher than the BLOCK pulse line exit nipple in order for the line not to get clogged with premix.
There is also a one way air check valve at the oil tank too. Replace that too.. It'll be like trying to suck a bowling ball through a garden hose. Grease often that fitting at the drive shaft coupler. Take out the thermostat but keep the spring and plunger in. Always clean the exhaust water inlet screen water inlet screen at the pump and also there is a screen at the exhaust pipe that you unscrew and pull out.
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