Rotax 720 rebuild

[Tyler08]

Hello!

So I recently acquired a 2001 Seadoo GTI. The previous owner didn't want to pay to have it repaired in the shop so it was given to me to play around with. Upon receiving it, most of the motor was apart, I removed the engine from the ski and striped the rest down to see what kind of damage I was dealing with.

It would appear that a bearing went in a connecting rod and sent fragments of metal and debris everywhere. Heavy scoring, and chunks missing from the cylinder sleeve l, pistons fubar, brass rotary gear stripped, rotary plate scuffed up, and small cracks in the lower crank case.

So I'd like to rebuild this thing but looking for any tips, advice, and if anyone can't point me in the best direction for parts! This project is a first for me but I'm a learn as you go kinda guy. I'll continue to post the progress here. Thanks.

 

[benjilafouine]

These guys are here in Canada: http://www.cvtech-aab.com/en/

I bought an engine from them last year (same ski as yours I believe) and it has been working flawlessly since then. I believe they also sell parts. You can also order in the US but because of our low exchange rate, you may consider finding the parts in Canada.

Benji.

 

[jcleary93]

With your rotary valve, rotary plate and engine cases all damaged your looking at much more than just a new crank and top end kit. You're much better off sending the engine off as a core and getting a rebuilt one in exchange

 

[96spxpos]

I was going to recommend the same thing... by the time you buy new cases, a crank, jugs, pistons, RV gear, etc...you'll be paying for a new one.. Id bolt it back together as best you can and use it as a core and go with a company like SBT..with the no fault warranty..itll run you about 7-800$ with the core. not sure on the shipping rates back and forth to Canada though. im sure theres a similar company up by you who does the core exchange program..
Only reason I said bolt it back together is because ive never heard of one of those companies taking a core back that's in pieces.. they might, but ive never heard of them doing so...

 

[Tyler08]

Update:

The crank shaft looks to be undamaged, along with the tubs. I figure I can buy a new cylinder sleeve to replace the cracked one, and have them both bored out. As far as I know they're able to be replaced. I priced out everything on eBay and I'm looking at around $500 for a top end rebuild kit, brass gear, cylinder sleeve, and used crank case. My question is, are all 720 crank cases the same? So if I get a 95 will it fit 2001 parts?

 

[jcleary93]

Yes I'm pretty sure they're all the same

 

[Matt Braley]

Yes sleeves can be replaced but it's not often worth it. My local machine shop charges $75 to replace a sleeve and $75 to bore one. No way am I gonna be in a common 720 jug for a hundred and fifty before ever buying a pistons and gaskets/seals for it!

As the guys above have said... I don't think your gonna come out ahead unless you can perform the machine shop work yourself.

Plus you want a rebuilt crank, not a used one. Check out those inner bearings on that 720 crank... I bet they are "chattery", they always are. Those are big pistons for that size crank and it has no counter balancer to help.

 

[Tyler08]

Did you have to send a core to be refurbished? Didn't see any completed motors on their site. Definitely interested.