Freestyle Delete

[Seas2699]

I’m looking to do a freestyle build sometime next winter and I’m just not sure which route to take.

Kawasaki: my original idea was to find a 300sx and cut up the hull then glass in either a 750 pump tunnel or try and get my hands on a 144 pump. Rocker the nose and shorten up the hull then drop in a 750 bored out to close to 800 and stroker crank. Ported with some massive carbs and pipe. And try to do some other things like either total loss or lightened flywheel to get some more bottom end out of it. This is close to what my 750 stand up has in it now and it pulls hard but I’m not sure how the bottom end would be for this build. I’m thinking with the right porting the motor would hit just as hard as a 701 or 760.

Yamaha: another idea would be to find either a square nose or fx1 and do some similar things here. Change up the hull and boost up engine to try and get an assload of bottom end. That being said I’m not a Yamaha person when it comes to skis. All I’ve ever known is kawi so doing this way would definitely be a new experience

I’m honestly not seeing any advantages going either way. Both are gonna be a ton of work and gonna need some serious upgrades. Let me know what you guys think


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[Pro-pulsion]

My thoughts are a little bit of both experience of my own, experience from others and postings from more of the others...but before you do any major top end work to a 750 Kawi, do yourself a favor and don't. Search for topics such as 750sx or SX-R crankcases sawing themselves in half, I believe both models use the same crankcases and possibly crank shaft. I've seen it happen to one, the same owner had it happen to 3 in total and I have read about it a good few times. It has something to do with the length of the connecting rods already being too long to handle heavy mods for very long, then snapping apart just below the piston, seems to be more prevalent on the PTO side too where it trashes the starter when it goes. Group K also has some very good info regarding this. The other side of it is parts. There is probably a 30:1 ratio of Yamaha parts floating around vs. Kawi parts. The 750's had wonky electrics where Kawi used several different configurations of the same motor and electrics but under different applications. All of them can bolt up the same, but unless they were always a matched set such as CDI and flywheel, you were either going to encounter a time bomb or a nightmare to get running properly. Also, the 750's were notorious for destroying flywheels. The rivets would get loose which if I recall would allow the ring gear to break away. I have seen 750 flywheels go bad like that and heard about happening too. I helped a fella make the what he thought was a tough call to convert to a Yamaha motor for his EME hull, once we had him set up to run it he said couldn't believe he never went that way to begin with, not only for parts availability and ease of working on it, but he loved the power delivery much more than how the Kawi produced it.

 

[Seas2699]

I have a 750 currently that is built close to what I would do to this ski. I haven’t had any problems with crank or anything else but I might just be lucky. The only thing I don’t have is a stroker crank. Cylinders are bored to 84mm, all port Work dropped 4mm and has an ocean pro head with 26cc domes. Never had any reliability issues with my set up or had it grenade on me. I’m less worried about the engine having problems and more Interested in the performance differences between the two.


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[Quinc]

I’m thinking with the right porting the motor would hit just as hard as a 701 or 760.

If your goal is to make your 750 as a good as a 701/760, why not just start with a 701 or 760? You can pick them up cheap or find a cheap yamaha sit down and pull the engine out. Porting templates from @yamanube for 25$. Also check out the my ski and build forum. You will find dozens of threads of people with the same thoughts of chopping up a ski and doing this or that to it, only to end up being a longer and more difficult experience until the ski sits at 60% done until it is sold for pennies on the dollar. Pick up a used bob or eme, fix that up and save yourself the headache. Or take the 200+ hours you are going to spend doing the work and get a part time job to pay for a new hull.

 

[Seas2699]

If your goal is to make your 750 as a good as a 701/760, why not just start with a 701 or 760? You can pick them up cheap or find a cheap yamaha sit down and pull the engine out. Porting templates from @yamanube for 25$. Also check out the my ski and build forum. You will find dozens of threads of people with the same thoughts of chopping up a ski and doing this or that to it, only to end up being a longer and more difficult experience until the ski sits at 60% done until it is sold for pennies on the dollar. Pick up a used bob or eme, fix that up and save yourself the headache. Or take the 200+ hours you are going to spend doing the work and get a part time job to pay for a new hull.

I in no way meant a stock 701 or 760. And I’m definitely not trying to drop 3-5 grand into just a hull. I have no problem putting in man hours. I’ve spent the last 6 months building 750s from hull up.


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[Pro-pulsion]

It's awesome that you have been doing well with your current set up, but the next could be the money pit. I just thought I would toss these out as a food for thought seeing as the 750's and 800's use the same crank and cases. This will about wrap up my input here

http://www.x-h2o.com/index.php?threads/800-sxr-engine-in-superjet-hull.45257/page-2
http://www.pwctoday.com/showthread.php?t=477000
http://www.pwctoday.com/showthread.php?t=64300
http://www.pwctoday.com/showthread.php?t=287482

^^ Just a few, I know I read it on the Group K site before too but the reason is due to certain modifications which I thought were rev limit increases. Due to the current length of the rods in these engines they are at about the max limit of tensile strength under normal conditions. I tried to find it but to no success. Anywho, I hope things work out for ya. I started off with a Kawi JS 300 B and loved it. It was a single but so light, that was a fun hull to play and learn on. Kawi does have a lot of good, but where they fall short it seems to in some circumstances cost in a big way where with a Yamaha it wouldn't. This is just purely for informative purposes though so you have some insight as to what can happen. I'm outty y'all