97' GS 720 cant figure out what is wrong

[SilverXP02]

Okay I bought the ski with a blown motor...the famous oil pump went out and it threw a rod. Got the engine rebuilt with new cases, put on a oil injection block off plate and completely removed the oil tank. Only other mods are a K&N air filter. Heres whats going on, It ran fine for about 10-15 mins, then it just quit, acted like the kill switch fell off. I reset the kill switch and took off again it quit again and never restarted. Took it home, took off the carb nothing clogged....checked the spark...has spark....I can spray starting fluid in the carb pour gas do whatever it will not fire. I have never seen a motor that wont do nothing with ether sparying it in.... checked all the fuses and still nothing I can find wrong. I have seized motors before and it has not siezed, though I have yet to check compression.... Someone please shed some light on me....thanks alot

 

[Dr Honda]

Removed the oil tank??

Did you do something else to lube your rotary valve gears?? If not, that's going to be your problem.

 

[SilverXP02]

the oil mixed in the gas dont lube it??

 

[Dennis]

I'm gonna let you tell him Dr Honda.

DAWG

 

[Dr Honda]

I'm gonna let you tell him Dr Honda.

DAWG

Thanks.

the oil mixed in the gas dont lube it??

No.

Most of the Seadoo Rotax engines use a rotary valve. That valve is spun using a set of gears between the 2 halves of the engine. Those gears need an oil supply. The 2 extra hoses on your oil tank keep those gears covered in oil. When you removed the tank... you removed the oil from them... and I'm very positive you will find that your valve is no longer spinning, and the gears have gone to a better place. (ie, they're dead)

 

[SilverXP02]

yep took the intake off and the valve is not spinning.... what I dont understand is why do you block off the oil pump if you gotta have it to pump oil to those gears.....So ur tellin me I gotta go buy a new oil tank, oil pump and then replace the gears in the case..:banghead:

 

[SilverXP02]

so my question is can I even block off the oil injection and how do I make all this work???

 

[Bills86e]

Sorry, you should remove the engine and disassemble (split the cases) to see if
the crank is damaged or not. Clean out all the shards (brass, metal bits) and see if the RV shaft is bent. Ect ect. Go from there. Bill

 

[SilverXP02]

So how do you run without the oil injection?? Why do they make block off kits if it screws up the motor :banghead:

 

[Bills86e]

Most rebuilders agree the only advantage is the span between carb rebuilds is less
as the oil helps prevent aluminum oxidation permiation thru the walls into the fuel circulatory. That after 3-4 years the small oil injection lines become brittle and can break, and motors can fail from no lubrication. Block off plates simply delete the use of these two oil lines. Most Racers will remove the tank & oil pump to conserver a few Oz of weight, and use heavy gear oil in the oil bath cavity, and tie together the old tank supply & return lines as a circulatory for the RV gear bath with a cap-able Tee fitting for adding any gear lub. Bills86e

 

[Dr Honda]

So how do you run without the oil injection?? Why do they make block off kits if it screws up the motor :banghead:

First... I'm a manufacture. I make parts that are (IMO) bad... and I make a few parts that are illegal as far as the DOT is concerned. (Vertical license plate mount is one of them)

Just because a part is made, doesn't mean you should use it.


OK... with that out of the way... if you want to go pre-mix, then what you do is remove the oil injection pump, and the big hose feeding it. Then cover the hole in the engine with the block-off plate. (you will also need to cap off the 2 nipples on the intake manifold) BUT... you still leave the tank in the hull, and the 2 hoses going into the engine. Then, you will want to leave about 1/2 gal of oil in the tank to keep the gears lubed.

What bill suggested is a RACE ONLY thing. First of all, the center crank seals leak, and gear lube is not compatible with our 2-stroke oils. So... when they start leaking, and you burn the oil in the gears... you won't know it until the gears fail. If you hook up the tank with 2-stroke oil in it, you can keep an eye on the oil level, and when it starts dropping... you know your crank seals are starting to leak.


But yes... the engine needs to be disassembled.


Personally, the failure rate on the SeaDoo oil injectors is very low, and most of the time the failures can be traced back to poor maintenance. (Cracked hoses, gelled oil from mixing brands, or a plugged filter) I recommend using it.

 

[SilverXP02]

Ok thanks alot for the info guys.... So the oil will just feed In the crank case without a pump? A new oil pump is only 55$ on eBay I might just go ahead and put it back on after I fix the gears...thanks agakn