Riddle me this…

[B_Stew]

Purchased a set of 98 GS 717 motor. Owner stated one was winterized incorrectly and was taking on water in the cylinder. No problem top end rebuild/winter project. The price was right.

Took it to the water just to observe for myself what was going on. Could clearly see water coming from between the crank case and the jug. Did a compression test. “Bad” cylinder 130 other cylinder 135.

Started tearing down the top end this evening only to find two of the bolts holding the jug down were just resting in place. They were also on the side I observed water coming out. What would cause these bolts to unthread? I was able to thread them back in and torque them down. I’m still disassembling at this point. It just didn’t seem like the motor had been opened up prior to this either. Found it kind of odd.

 

[mikidymac]

Never seen that.

Someone had to do it. Install a new base gasket and follow the manual for torque and thread locker and run it.

 

[AKnarrowback]

Agreed. Never have seen that.

 

[B_Stew]

Never seen that.

Someone had to do it. Install a new base gasket and follow the manual for torque and thread locker and run it.

Full rebuild?

 

[AKnarrowback]

Full rebuild?View attachment 56760

Take pictures of the piston sides/skirts. They look scored in the shot you have there.

 

[B_Stew]

I was more worried about the moisture in the crankcase then the top end. Top end is an easier fix.

 

[etemplet]

Do the top end. Too cheap not too once you open it up.

As for the bolts... someone left them loose or didn't torque properly. They probably forgot.

I'd clean the bottom end up as well, flush it, blow it out and put a level of oil in there and let it soak. Good Luck !!

 

[B_Stew]

Do the top end. Too cheap not too once you open it up.

As for the bolts... someone left them loose or didn't torque properly. They probably forgot.

I'd clean the bottom end up as well, flush it, blow it out and put a level of oil in there and let it soak. Good Luck !!

What’s the best method to flush it?

 

[etemplet]

What’s the best method to flush it?

Well I'm sure some won't agree but gas or diesel... You are just giving it a rinse. Pour the contents into a clean container and see what came out. Should be discolored but not full of particles especially heavy ones. I blow it with air and get it is dry as I can then I pour injection system lube in there, turn it and listen and feel the bearings. If it all feels good, I'll let that oil sit in the casing till I'm ready to assemble the engine.

It's just an extra measure that I do when I'm not replacing the crank. It isn't meant to fix anything just filter out whatever junk accumulated over the years like cleaning the fuel tank. Good Luck .

 

[mikidymac]

IF you have rust on the crank it is done and the bearings are done. I would at minimum split the cases and inspect the crank for any rust and new outer crank seals.

 

[B_Stew]

Well I'm sure some won't agree but gas or diesel... You are just giving it a rinse. Pour the contents into a clean container and see what came out. Should be discolored but not full of particles especially heavy ones. I blow it with air and get it is dry as I can then I pour injection system lube in there, turn it and listen and feel the bearings. If it all feels good, I'll let that oil sit in the casing till I'm ready to assemble the engine.

It's just an extra measure that I do when I'm not replacing the crank. It isn't meant to fix anything just filter out whatever junk accumulated over the years like cleaning the fuel tank. Good Luck .

Ohh boy. So I’ll need to pull the engine to flush it correctly or at least make it a lot easier process. I do enjoy the simplicity of the two stroke. The 454 I rebuilt in my boat wasn’t so easy to work on.

 

[etemplet]

Nah, you don't need to pull the engine that just makes for extra work. From my experience, the engine probably isn't aligned worth a crap. LOL Give the motor mounts a strong pull. Make sure it's all tight.

 

[B_Stew]

Nah, you don't need to pull the engine that just makes for extra work. From my experience, the engine probably isn't aligned worth a crap. LOL Give the motor mounts a strong pull. Make sure it's all tight.

The motor is actually nice and tight on the mounts!
Also if there was actual water in the crank case wouldn’t there be signs of water in the oil system since the crankcase is recirculating oil?

 

[mikidymac]

The motor is actually nice and tight on the mounts!
Also if there was actual water in the crank case wouldn’t there be signs of water in the oil system since the crankcase is recirculating oil?

No they are separate.

If there was any water sitting in the crankcase the crank has a 99.9% chance of having rust.

 

[Notoriousscottyb]

Purchased a set of 98 GS 717 motor. Owner stated one was winterized incorrectly and was taking on water in the cylinder. No problem top end rebuild/winter project. The price was right.

Took it to the water just to observe for myself what was going on. Could clearly see water coming from between the crank case and the jug. Did a compression test. “Bad” cylinder 130 other cylinder 135.

Started tearing down the top end this evening only to find two of the bolts holding the jug down were just resting in place. They were also on the side I observed water coming out. What would cause these bolts to unthread? I was able to thread them back in and torque them down. I’m still disassembling at this point. It just didn’t seem like the motor had been opened up prior to this either. Found it kind of odd. View attachment 56726
View attachment 56727
View attachment 56728

Too much beer not enough blow

 

[B_Stew]

No they are separate.

If there was any water sitting in the crankcase the crank has a 99.9% chance of having rust.

On the 717 the crankcase oil is separate from the injection oil? I’m most certain crankcase is a free flowing loop back to the revisor.

 

[themk]

The 717 doesn't have a counterbalance, and so there is no oil held in the engine. The crankcase is lubricated (like in all small 2-strokes) from the oil/fuel mixture (which is injected). No oil is returned back to the oil tank, it's all combusted as part of the combustion process.

If there is water down in the crankcase then the engine needs a complete bottom end repair too.

On a 2-stroke the crankcase is used to compress the air/fuel mixture before it goes up to the cylinder via the intake port. That is how those pieces are lubricated.

 

[mikidymac]

The 717 doesn't have a counterbalance, and so there is no oil held in the engine. The crankcase is lubricated (like in all small 2-strokes) from the oil/fuel mixture (which is injected). No oil is returned back to the oil tank, it's all combusted as part of the combustion process.

If there is water down in the crankcase then the engine needs a complete bottom end repair too.

On a 2-stroke the crankcase is used to compress the air/fuel mixture before it goes up to the cylinder via the intake port. That is how those pieces are lubricated.

This is not true.

The 787 and smaller engines like 720 all have a rotary gear that is in an oil flooded chamber supplied by the oil tank. It is separate from the oil that lubricates the crank and pistons from the oil injection or premix. This rotary chamber is supplied by the oil tank but it is just gravity fed and doesn’t circulate.

Even converting to premix which isn’t recommended you still have to supply oil to the rotary gear chamber.

 

[themk]

You are correct, I had forgotten about the rotary valve oil. Thank you for clarifying.

 

[B_Stew]

This is not true.

The 787 and smaller engines like 720 all have a rotary gear that is in an oil flooded chamber supplied by the oil tank. It is separate from the oil that lubricates the crank and pistons from the oil injection or premix. This rotary chamber is supplied by the oil tank but it is just gravity fed and doesn’t circulate.

Even converting to premix which isn’t recommended you still have to supply oil to the rotary gear chamber.

Okay so the top line and bottom line are both feed lines and Just supply oil when need?

 

[mikidymac]

Okay so the top line and bottom line are both feed lines and Just supply oil when need?

Bottom is the feed top is just the air vent. So gravity will fill the cavity to the level of oil in the tank.

 

[1of500]

That crank IS DONE!