1996 gsx pto piston

[bmcgee7469]

I have rebuilt the top end twice last year with WSM Platinum pistons only to have the pto side piston get ruined. The first rebuild lasted about 4 times out on the water and the second rebuild lasted only about a 1/2 hour hearing it starting to knock and losing power. Pressure testing the motor after rebuilds have shown no leakage and held pressures according to the shop manual.
The cylinders are 1mm over stock and aqre in good shape. Luckily for the pto side, trailered before damage was done to the cylinder. I am considering a set of wiseco's.... Any advice would be helpful!

 

[bmcgee7469]

I have rebuilt the top end twice last year with WSM Platinum pistons only to have the pto side piston get ruined. The first rebuild lasted about 4 times out on the water and the second rebuild lasted only about a 1/2 hour hearing it starting to knock and losing power. Pressure testing the motor after rebuilds have shown no leakage and held pressures according to the shop manual.
The cylinders are 1mm over stock and aqre in good shape. Luckily for the pto side, trailered before damage was done to the cylinder. I am considering a set of wiseco's.... Any advice would be helpful!


I'm sorry for not posting that it is the 787 motor.

 

[Bills86e]

A guess is that the Mag carb has an Aluminum Oxide & oil mineral clog (like liquid steel) and the pto carb suffers a lean condition. 99% of seadoo probs are a fuel
circulatory issue. Mikuni even states a warning of the effect, and suggests when
rebuilding to paint. We techs also GREASE all carb exteriors, linkages ect, and aluminum selector valves as once gas leaves the tank and enters the bafel, its a
recirculated fuel mix that will grab moisture thru any aluminum wall and pulls the
oxide into the circulatory. Its like adding hardener to Bondo resin! Bills86e

 

[voodoo]

The burnt cyls is the effect, the cause is lean-out or oil problem which can be as easy as flushing the oil system with kerosene while using premix 40-1 until you know for sure it is drinking, the fuel problems can be grey lines dissolved and clogged carb filters, clean out the steel gas can trash and make sure there are no air leaks causing fuel lean-out.

 

[seadooya]

have yuo gone thru the carbs? Did you replacethe grey fuel lines? Did you install an aftermarket impellor? If you wentthru the carbs, are the lsa/hsa settings correct?

 

[bmcgee7469]

The fuel lines were replaced and the carbs were rebuilt. everything checked in spec. Everything is stock besides the bore. Could it still be a carb issue? Does the coolant system flow through the cylinders and down through the lower case at all?

 

[bmcgee7469]

Every thing checked out ok. hsa/isa were adjusted properly and oil pump was aligned properly. Carbs were rebuilt but not repainted or coated with grease.

 

[Bills86e]

Water can get in gas from the suppier tanks, so do a pre-ride dump-out of the fuel
bowl (water separator/filter) as a heads-up to gas contamination. A water molecule
is much larger than gas, so it has a hard time exiting the carbs, also it blocks gas flow and has been cause of many of engine failures. Add a drier/disipator to fuel system when water is detected. It is heavier than gas and lays in tank bottom when sitting. Bills86e

 

[bmcgee7469]

Thanks for your help...Keep cool this summer!