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Rebuilding a XP 720 Motor

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Guyph_01

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Hi Guys,

I bought a 1995 XP 720 with the engine in bits. I'm gonna attempt to rebuild it.
I joined to learn more about them, the little tricks i can do to it while building it, get help and advice and by the looks of it, find parts for it:)

sdc19870.jpg


sdc19869.jpg


sdc19873.jpg


I had a quick look at it and i'm starting to gather info, manuals and costs.

I've noticed that the top 'outside' of the head, where the rubber seal for the rocker cover goes has its outside lip broken off where the rubber seal runs into. Is this fixable or is it better to get a another good head?

Also, This sounded very weird to me but the previous owner told me that he blocked off the oil pump and added 20:1 oil in the fuel. Is that Safe??? has anyone ever done that??

Will post more soon:)
 
Guyph_01 said:
Hi Guys,


Also, This sounded very weird to me but the previous owner told me that he blocked off the oil pump and added 20:1 oil in the fuel. Is that Safe??? has anyone ever done that??

Will post more soon:)
Click to expand...


Nope... and that's probably why the engine is in a box.


Here's the deal... unlike most 2 stroke engines... Seadoo uses a rotary valve. The Gear case in the Rotax engine is fed an oil bath via the oil tank. We see it several times, every year, where guys that don't really understand a Rotax engine, removes the oil injection system, and the center section of the engine eats it self.

If you want to go to a pre-mix on a 720 Rotax... you have to leave the oil tank in the hull, and hooked to the center section of the engine. Then... you just remove the pump, and seal up the hoses in the injection system ONLY. At that point, you run 40:1, and you still need to run an API-TC oil (TC-w3 oil will lead to a short engine life)

Last thing... the seadoo oil injection is SUPER reliable, and I don't know of a single ACTUAL pump failure. Most of the time when someone says "My engine died because of the stupid oil injection"... the reality of it is, the system had been neglected, and a hose broke, the filter was clogged, or the injection nipples were coked over.

Good luck with the engine build.
 
Hello and welcome.
You have come to the right place.

For parts we have a very good source with minnetonka4me or 99spxxx. You can pm either one for prices.
 
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Hi,

thx for the reply. I knew something was up with that oil pump thing. I don't see how someone can out smart seadoo engineerings by removing something as important as a oil pump and that it must have an essential role to play or else it would not have been there in the first place.

Thx for the names for parts, i'll try and pm them:)
 
Hi,

I think i was able to pm minnetonka4me but the forum says that 96spxxx was not found:S Is that the right name?
Thx
 
That should be Jess at 99spxx not 96....he and Minnetonka4me are brothers In very different locations of the USA.

what kind of shape are the motor parts in?
 
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Its ok, Like i said i think i need a new head, the bore looks ok, might need new rings maybe new pistons too. I think i'll either rebuilt the crank or just buy a rebuilt one to save the hassle and i need all the oil pump system gear. Quite a bit of work but i like it and keeps me busy:)

I've just spotted this
http://www.ebay.com/itm/sea-doo-720..._Watercraft_Parts&vxp=mtr&hash=item588d5d4705

Not too sure what he is covering with his hand but what do you guys think? Is that a reasonable price?

My main issue is i need to make sure that the parts will definitely fit my engine. Is there engines numbers and parts number that we can verify this when i buy new parts? As i will need the parts shipped to Australia and can't afford to ship the wrong parts.

Basically for now i need, and would anyone know where i can get:
A rebuilt XP720 crank incl bearings rods and seals
Head gasket kit
A head
Oil pump complete setup including tank lines, pump etc. (might be best to get a new pump or a recond one??)

Thx
 
:( 99spxxx has no more pm space. Anyway if anyone reads this and can help

Hi,

As above, I would need the parts shipped to Australia Perth WA. I was wandering if you can help me with either the new or used parts.

A rebuilt XP720 crank incl bearings rods and seals
Pistons and rings (new)
Head gasket kit (new)
A head (new or used)
Oil pump complete setup including tank lines, pump etc. (might be best to get a new pump or a recond one??)


Hopefully I can get a good price for you guys so postage doesn't kill it for me.

Awaiting your reply
Kind regards
Guy
 
Yup the S/H is going to suck and cost more than the part.

If 99 or minne has all the parts is may be worth to spend one shipping charge.

Another idea is find another engine that is bolt in ready? Then you can have spare parts. A rebuilt crank is $300-500. Pistons and hone/bore is $300 if you send cylinders to company in US.
The cyl head is another $50 bucks.
You can get another used engine with good compression for close to that.
 
That is a kit with bearings and rods.
You will need shop to rebuild crank.
Buy a new crank with rods already installed.
Those run close to 400 bucks.
Or google hotrod crank as other option
 
SBT has all the parts you need, I don't know if you will like the price, they also rebuild engines.

Lou
 
Lou - his hand is probably covering the maker of the rebuild kit (WSM). As "ocod" noticed this is just a rebuild kit and you would need a shop to press the crank together with these new parts. The part number 010-317 in the picture is for the WSM rebuild kit, that others on eBay sell for $199. I have had good success with some WSM parts, but the reason he is probably hiding the WSM logo is that they are pretty much the low end parts that are the cheapest. Probably best to get an already rebuilt crank, on eBay or SBT.
 
Yeah i'm trying to consider all my options:) I though of getting a rebuilt crank but postage to Australia will be a huge killer:(
On Monday i'll ring around Australia to the few SeaDoo shops and see what i can find:)

Also, i have one piston that has little holes on the top due to something getting in the cyl. Should i just get new pistons or can i try and get a second hand piston and only get new rings for them? I know new is always better but i'm trying to save costs:)

Anyone have some new parts they bought for a build similar to mine and never ended up using them? I'd be keen to buy them and hopefully save a bit that way:)
 
Also, i found a 717 manual. Is it the same and the 720 and i can use it to rebuild my 720engine? or will it be different with different specs etc?

Also, when looking at the Rivamotorsports parts page, why are the gaskets with either 0.3, 0.4, 0.5, 0.6, 0.7mm think to choose from?

And is there a seal kit for the axle shaft that turns the prop and prevents water from going in? what is it called?
 
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There are different thickness of base gaskets to get the squish right. Usually the kits come with one of each.

The pumps have rebuild kits with the seals, but you have to have the correct bearing/seal drivers.
 
I went though a very similar build on my 3D, getting parts to Perth sucks- long waits and heavy shipping.
I got Brendon at Seadoo Central in Ascot to do the actual build and he helped me out a lot with parts etc.
I highly recommend him, though right now its silly season down there so he is busy as.
Mine isnt an XP but if you want to check out what the 720 should look like in my HX fire me a PM
 
the 717 engine is the 720 engine ..... it really is a 717 from seadoo but most people i guess find it easier to say its a 720
 
Thx for the replies guys:)

Ok so, What does getting the right squish mean and how do i know what thickness gasket to use?

Also, i have one piston that has little holes on the top due to something getting in the cyl. Should i just get new pistons or can i try and get a second hand piston and only get new rings for them? I know new is always better but i'm trying to save costs
 
If the price difference between a used and new piston is small then go new but I'm sure if a used piston is in good shape you can get away with a used one

either way now tha ti think of it imo i would go new you want the motor to last and you get what you paid for from what i see around 50 bucks for a new piston kit id go new
 
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Ok and would i then be able to only buy new rings? as most of the kits i see come with both....

Also rings sizes, what and how do i know what i should get?

Sry if some of my question seem dumb but its my first engine rebuild:)
 
I'm going to be brutally honest here, I don't know how much you paid for the ski, but it looks to me pretty much of a basket case. Before you start any serious work on the ski you might want to consider your options. If I'm overstepping by bounds please let me know.

When you consider all of the costs, once you get the motor rebuilt or buy a rebuilt motor you really don't know about the condition of the rest of the ski, ie MPEM, pump, drive shaft, steering, starter, carbs., oil pump, etc., etc. Also you will need to either rent or buy an engine alignment tool. Plus you will have the added expense of shipping, and possibly customs. You could wind up spending a lot more money than the ski is worth.

You might be better off parting the ski you have, and buying a running ski. Like I said please don't take this as a criticism, I'm just trying to put myself in your place.

Lou
 
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