engine rebuild advice...

[reyb]

I'm rebuilding a '96 Kawasaki 750 jetski motor because the rings on one of the pistons seized and basically broke the piston. While taking the motor apart I noticed that one of the exhaust port got damaged on the lower part of the port(see example image attachment). I'm thinking that since the damage is on the lower part of the port, then I can't really see what effect it would have, but I'm not sure, so I'm hoping someone here can give me some advice. Is it ok? Should I resleeve?

Thanks,

Rey


Ooops, I think I posted in the wrong area.

 

[aussie]

that will put out your intake timing it may not push intake gases from the crank case to the cylinder bore and the rings may not go completely past the hole so i would say its junk

 

[reyb]

Thanks Aussie.

 

[aussie]

i was hopeing someone else would make a comment too but do it rite from the start it always cost alot to do it that way but in the end its cheaper than doing it twice

 

[spareparts]

I'd figure Skools would chime in on this thread, he's the resident PWC guy

 

[reyb]

Doing some research right now and one of the hurdles is the resleeving. There are some articles about putting the head in the oven(400 degrees) and pressing out the sleeve and then pressing in the frozen new sleeve in. Some people say its' relatively easy and some don't. I'm currently look at around $200 for a new top end kit(2 pistons and gaskets), $65/sleeve and $225 to install the new sleeves and bore.

 

[Richie Rich]

thats a cheap price for peace of mind.....i wouldnt chance it for that price...add another zero, maybe....not that

 

[Skools Out]

if it is like that the motor won't run if you reuse that sleeve, that sets to lower end timing on a piston port Kaw motor. i have ground them before to adjust the timing for different HP curve, you could do that but it's a ton of machine work and requires different piston timings as well. my old JS440 i have done all that to, it took about a yr to get it rebuild with all the timing working, but it's now bored to a 575 plus the compression will change alot doing that mine went from factory 90 psi to now 225 psi which then requires the crank plates to be welded or it will twist the crank. i would have the crank welded either way, if you raise the compression alot you'll need a goki hp starter to turn it over. i changed the head on mine as well which you should do while it's apart find either a Westcoast or PJS or JetSport HP head. if you do all that you will have to convert to the twin carb setup from JetSport perf parts. that's what i had to do, i went from a single 38mm carb to twin 46 mm carbs now but if you do that it requires the exhaust timing to be fixed and you must run the PJS twin 6 inch exhaust which is what mine now has. but they will fly if you do all this. mine went from a factory WOT @ 9k rpm @ 24 mph to now WOT @ 19k rpm and 87 mph, the coast gaurd clocked me whoops in a no wake zone 2 summers ago. your best plan is look on ebay and buy a used but good set of 750 juggs with some good pistons, i do have 40 or 50 sets of kaw pistons if you know what MM your bore is let me know i may have a set. as for the head change if you only change to an aftermarket head no twin carb change required, if ya need something let me know.

 

[Skools Out]

here's best deals for ya

http://cgi.ebay.com/ebaymotors/KAWA...Personal_Watercraft_Parts&hash=item4aaae86bc1

i would do this while apart for sure

http://cgi.ebay.com/ebaymotors/Kawa...Personal_Watercraft_Parts&hash=item256375f34d

http://cgi.ebay.com/ebaymotors/KAWA...Personal_Watercraft_Parts&hash=item2a102f6f7e

http://cgi.ebay.com/ebaymotors/Comp...Personal_Watercraft_Parts&hash=item45fa6d2721

or consider this upgrade

http://cgi.ebay.com/ebaymotors/KAWA...Personal_Watercraft_Parts&hash=item4aaae86bc5

http://cgi.ebay.com/ebaymotors/kawa...Personal_Watercraft_Parts&hash=item27bab3c63c

 

[reyb]

Wow, where to begin ... That's some good info you shared and thanks for the links too. I did look at ebay but I'm reluctant to buy a used engine only because I have no idea what condition they're really in. I currently have two '96 Kawasaki STS jetskis and the one I'm rebuilding the engine and both of them will require carb rebuilds and primer pumps replaced. I was reading up on those aftermarket heads and they're not cheap. That one link you had seemed reasonable, but I gather that the aftermarket heads need to be matched with the compression reading of the engine. I'll probably just stay the stock route. However, I do have some questions for you if you don't mind

o I'll resleeve the one cylinder, but should I resleeve both?
o I've seen articles on the web about do-it-yourself resleeving...baking the cylinder
at 400 degrees, pushing out the old sleeve and with a sleeve kept in a freezer, then
press it in. Have you done this before? If so, did you need to use a press?
o One of the jetskis, when it was running, would gradually cut out while running. We
would ride for an hour or so and then the engine would gradually cut out more and
more. I"m hoping that a carb rebuild will fix that problem, but the cutting out doesn't
happen in the beginning. Any ideas what it could be? electrical?

Thanks Skools!

Rey

 

[Skools Out]

Wow, where to begin ... That's some good info you shared and thanks for the links too. I did look at ebay but I'm reluctant to buy a used engine only because I have no idea what condition they're really in. I currently have two '96 Kawasaki STS jetskis and the one I'm rebuilding the engine and both of them will require carb rebuilds and primer pumps replaced. I was reading up on those aftermarket heads and they're not cheap. That one link you had seemed reasonable, but I gather that the aftermarket heads need to be matched with the compression reading of the engine. I'll probably just stay the stock route. However, I do have some questions for you if you don't mind

o I'll resleeve the one cylinder, but should I resleeve both?
o I've seen articles on the web about do-it-yourself resleeving...baking the cylinder
at 400 degrees, pushing out the old sleeve and with a sleeve kept in a freezer, then
press it in. Have you done this before? If so, did you need to use a press?
o One of the jetskis, when it was running, would gradually cut out while running. We
would ride for an hour or so and then the engine would gradually cut out more and
more. I"m hoping that a carb rebuild will fix that problem, but the cutting out doesn't
happen in the beginning. Any ideas what it could be? electrical?

Thanks Skools!

Rey

first the aftermarket heads don't change anything but raise your compression it will work fine on your motors

second no you don't want to put the sleeve in as they have to be lazer set for timing reasons to line up all the ports

third that sounds like a bad stator in the cutting out or it's getting wet while riding in the flywheel area.