717/ 720 Rotax complete rebuild recommendations

[chazmcgee12]

717 Rotax inner seals went and I am looking for recommendations for rebuild kits and parts. Hear some bad things about sbt and wsw but I’m having trouble finding oem parts. I want to rebuild the whole engine at this point so I need a crankshaft piston rigs rv shaft and gasket. 2002 gti so leaning on reliability… for the most part.

Swallowed a bolt from the carb plate and I think the brass rv shaft shredded and then just ate the seal.

Deleting oil injection and going with dual carbs

 

[mikidymac]

No reason to delete the oil injection or go dual carbs.

WSM parts are perfectly fine and better than SBT. You just need a reliable shop to bore the cylinders for the new pistons like Group K. Pro-X pistons are very good and probably the best aftermarket, just below OEM.

 

[Bacardi]

Get a new crank, new complete gasket kit, use 5 hole gasket on cylinders base, rebuild the carbs with OEM mikuni to factory specs or slightly enrichment on high speed screw, put Prox pistons, torque everything to spec, do not use loctite 518 on crank cases, instead use any good silicone sealant resistent to gas, use loctite 243 on the bolts that need it, check the clearence on the rotary valve (this is important).
Do not delete oil injection, put new hoses, and new clamps alignment the put correctly and use only a good Api Tc 2 Stroke oil, i use Castrol Power 1 Ultimate 2T (may not be available in your country, if not, Amsoil Interceptor.
On the first tank, you should add oil to the fuel, 50/60:1 is good if the runing the oil pump at the same time, this prevents the initial start, if the oil pump is not correctly bleeded.
You will have an engine good for many many hours.

Cylinder to piston wall, minimum is 0.10mm max is 0.20mm, set them to 0.12/0.13mm, they will be slightly "loose", but you will have a lot less chances of cold seizure, because marine engines are always on throttle and our engines run on open loop cooling the pistons will expand more than the cylinders.
Any doubts, just ask.

 

[chazmcgee12]

No reason to delete the oil injection or go dual carbs.

WSM parts are perfectly fine and better than SBT. You just need a reliable shop to bore the cylinders for the new pistons like Group K. Pro-X pistons are very good and probably the best aftermarket, just below OEM.

Yeah I emailed group k a couple weeks ago still haven’t heard anything. Heard they’re the best

 

[chazmcgee12]

Get a new crank, new complete gasket kit, use 5 hole gasket on cylinders base, rebuild the carbs with OEM mikuni to factory specs or slightly enrichment on high speed screw, put Prox pistons, torque everything to spec, do not use loctite 518 on crank cases, instead use any good silicone sealant resistent to gas, use loctite 243 on the bolts that need it, check the clearence on the rotary valve (this is important).
Do not delete oil injection, put new hoses, and new clamps alignment the put correctly and use only a good Api Tc 2 Stroke oil, i use Castrol Power 1 Ultimate 2T (may not be available in your country, if not, Amsoil Interceptor.
On the first tank, you should add oil to the fuel, 50/60:1 is good if the runing the oil pump at the same time, this prevents the initial start, if the oil pump is not correctly bleeded.
You will have an engine good for many many hours.

Cylinder to piston wall, minimum is 0.10mm max is 0.20mm, set them to 0.12/0.13mm, they will be slightly "loose", but you will have a lot less chances of cold seizure, because marine engines are always on throttle and our engines run on open loop cooling the pistons will expand more than the cylinders.
Any doubts, just ask.

Awesome thank you i appreciate it.

Get a new crank, new complete gasket kit, use 5 hole gasket on cylinders base, rebuild the carbs with OEM mikuni to factory specs or slightly enrichment on high speed screw, put Prox pistons, torque everything to spec, do not use loctite 518 on crank cases, instead use any good silicone sealant resistent to gas, use loctite 243 on the bolts that need it, check the clearence on the rotary valve (this is important).
Do not delete oil injection, put new hoses, and new clamps alignment the put correctly and use only a good Api Tc 2 Stroke oil, i use Castrol Power 1 Ultimate 2T (may not be available in your country, if not, Amsoil Interceptor.
On the first tank, you should add oil to the fuel, 50/60:1 is good if the runing the oil pump at the same time, this prevents the initial start, if the oil pump is not correctly bleeded.
You will have an engine good for many many hours.

Cylinder to piston wall, minimum is 0.10mm max is 0.20mm, set them to 0.12/0.13mm, they will be slightly "loose", but you will have a lot less chances of cold seizure, because marine engines are always on throttle and our engines run on open loop cooling the pistons will expand more than the cylinders.
Any doubts, just ask.

Awesome, thank you i appreciated it! Already rebuilt my carbs just trying to find the best guy to rebuild crank and bore cylinder

 

[chazmcgee12]

Just curious because I saw this on other forums too. Why are people against premix. I definitely would feel more comfortable blocking the oil pump off due to a blown mercury 200 that blew due to an oil line failure. I run pre mix in that and have no issues

 

[mikidymac]

On these you still have to supply the rotary gear with oil so you still need an oil tank or a connected hose to keep checking th eoil level on.
Also these oil pumps just don't fail. The only thing that can fail is the small 3/32" oil lines from the pump to the intake but they last 20+ years so just change them every 20 years to be safe.

These are also a variable rate oil injection pump that isn't related to rpm so at idle they provide almost no oil which is good to prevent fouling plugs and more than premix at wide open throttle so you will use less oil and get as good or better engine oil than premix.

I would call Group K, I haven't had much luck with email, they are old-school.

 

[chazmcgee12]

I just checked my cylinder to see if they were in spec of the wear limits because if I don’t have to bore it I’d rather not due to how clean they are. They are within limits (82.03<81.96) before honing but the only thing that I’m worried about is the diameter of the pro X pistons if anyone knows the exact size of them because I was reading it has to be a specific clearance piston to cylinder.

I know the pistons are not going to be exactly 82 mm and I think it’s a .10 clearance if anyone out there has the standard pro x size it’ll save me some time. thank u

 

[mikidymac]

If there is nothing wrong with the cylinder or pistons then why replace them? If everything is perfect run it.

 

[chazmcgee12]

Before, when it was running it was at 125 lbs each cylinder and to my knowledge it’s the original piston with new rings. I just figured if I’m already tore apart mine as well replace and rebuild the whole motor. Unless u guys suggest otherwise.

 

[mikidymac]

No, 125 is low. I am surprised that you are showing that low of compression and the cylinders are still within spec.
Did you use a bore gauge and check multiple places for taper too?

 

[chazmcgee12]

No, 125 is low. I am surprised that you are showing that low of compression and the cylinders are still within spec.
Did you use a bore gauge and check multiple places for taper too?

Yea, my guess is the rings they didn’t look the best. To my knowledge my friend had this ski and just honed the cylinder put the same pistons in and either used different rings or bought new ones.

 

[mikidymac]

Then the compression should be good if he put in new rings and the cylinders are within spec.
If it was mine I would bore to 0.25 over and be done with it for years. Typically just new pistons and rings in std bore don not yield lasting compression numbers.

But if you really want to do just pistons and rings get STD Pro-X.

 

[chazmcgee12]

I’ll take ur advice and bore it, rather safe then sorry

 

[mikidymac]

I think Group K still is the most reasonable for boring but you have to ship. He does chamfer the ports perfectly and is exact on his clearances. He can also supply pistons.