440/750 swap help

[bobby.b.440]

Hey all new guy to the forum, I'm doing a 440/750 swap and would appreciate some advice! I'm starting with an 81 js440 that has basically no hours. I started off by just porting it 135/189, drying out the pipe, cut head, bored the nozzle, 38sbn, Kerker shorty. So after ~ 20 hours of working that 440 IRON cylinder over to perfection (worst OEM porting/port matching I've ever seen, I've ported more than a few engines in my day) I was a bit underwhelmed lol! My little 440 still planes out slow as hell (I'm 195lbs) terrible throttle response everywhere, solid 46MPH GPS it revs to the moon. so I got a 96 750 something or other on craigslist for $250 and I'm done with the 440.

First off can someone ID this engine, title says 96, should be the BIG PIN right? case is grey, cylinder black, red head, dual keihn 40s, the pipe is green. Im thinking maybe someone slapped a 650 top on it? Will this drive coupler work and who has the best adapter plates, ebay or what?

I have a spare 550 pump but I wanted to use the 440 pump since its mint, already have a brace. the 550 stator i have is beat up. Can the rev limiter be removed? can I use the 440 ignition stuff? Im gonna probably port it, run a short pipe and rev it out so the 440 pump makes sense. could care less about top speed, was thinking iether a 13/18 or a 15.5 with a scoop grate, any input on pump/prop selection is welcome.

 

[papadon]

That is a 750 engine. Check intake manifold side, if there are 10 studs it is small pin, if 12 big pin. Any compression readings?
Looks like someone did a really sloppy job putting this back together.
If I were in your shoes, I would fully dismantle the engine, replace gaskets and crank seals and measure everything just to be on the safe side.
15.5 pitch will be very low on a 750 engine. On my last 650 conversion with a slightly ported engine, pipe, carb and 550sx pump I was running a solas 17 pitch and it needed more pitch for good top end.

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[bobby.b.440]

130 on each hole. I'm definitely gonna tear the top end off and port it, new gaskets, maybe cut the head... it looks super sloppy with blue rtv smeared everywhere lol. should I worry about too small of a prop cavitating or is that just some internet myth? I ride salt water in the gulf so the top end doesn't matter its rarely calm enough to go better than 40.

 

[papadon]

When I tried the 550sx/650 first time with the stock prop( I don't know pitch ) it was really cavitating out of the hole.
With the 17 there was no cavitation and had good bottom end, but it was like having the ski in low gear.


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[bobby.b.440]

I got 10 bolts on the intake, so that makes it a small pin in 96??

 

[bandit88]

96 should be a big pin. What is the serial number on the crank cases? Very possible that is not the original motor, defiantly not the original paint.

 

[bobby.b.440]

0H750BE012354

 

[bobby.b.440]

I'm thinking it's a small pin 750 that someone slapped a 650 top end on at some point. I'm doing the carbs now, I'll take it out on the weekend and see if it runs worth a poop before I do anything. If it runs good I'll use it, if it's got lots of problems I'll flip it and find another doner.

 

[bobby.b.440]

I got Franken engine running but it sounds like it's on the rev limit and won't break 4k, starts and idles good. New carb kits, new plugs, 130psi both holes. Probably an ignition problem? Broken Reed? What's common on these turds I know nothin about kawis.

 

[bobby.b.440]

Never mind guys that was a tough one, unplugged the temp sensor runs like a champ lol.

 

[bobby.b.440]

 

[bobby.b.440]

Hit the saltwater today got a solid 35mph lol trim stuck down full of water ect.. bore measures just under 84mm. Small pin bottom with a max bored 650 top (tall exh port) this bitch is over 800cc lol it hits the pipe hard as licorice and runs out of steam by 6500 the tune up is garbage the pipe is waayyyy too long. Lots of potential here I think.