SX/SXi/SXi Pro Big pin, little pin 750 sxi questions

[ski_crazy]

What is the facts about "big pin" and "little pin" motors? I have a 96' 750 sxi. How do I tell the difference in the two and find out which one I have. I'm clueless about this subject. Thanks for any help.

 

[Crab]

small pin 10 intake bolts, 12 on big pin.

 

[ski_crazy]

Thanks crab.

What does the "pin" refer to?

 

[john zigler]

"big pin" is in reference to the size of the crank pins.

they really are two completely different motors though. port timming is different between the two, cases, cyls, pistons, head, ect, are all different.

your 96 SXI should have the "big pin" motor, unless some one switched it.

all "small pin" motors were single carb motors, and crab is correct, only had 10 intake mount bolts.

hope this helps.

zig

 

[ski_crazy]

Mine only has 10 bolts on the intake manifold. It is a dual carb with R&D intake though.

 

[Crab]

Small pins have the best freeride porting.

 

[djkorn1]

Someone changed it to duallys. It is a small pin...

 

[sflsurfrider]

"big pin" is in reference to the size of the crank pins.

they really are two completely different motors though. port timming is different between the two, cases, cyls, pistons, head, ect, are all different.

your 96 SXI should have the "big pin" motor, unless some one switched it.

all "small pin" motors were single carb motors, and crab is correct, only had 10 intake mount bolts.

hope this helps.

zig

good thread... im a bit clueless on these crazy ever-changing kawis too.

of the cases, cyls, pistons, cranks, heads, etc..... which parts are interchangable?

are all kawi 750 flywheels, stators and electrics interchangable?

 

[ski_crazy]

Is one better than the other? Is there anything I should change? The motor is pulled and sitting on my work bench. Now would be a good time to change anything that needs it. Specs are, Ocean Pro f/a's, R&D intake, R&D head, Factory Pipe exhaust manifold and full Factory Pipe.

Also I pulled the spark plugs after a four hour ride, they were brand new, and the back cylinder plug was covered in what looked like car motor oil and the front plug was spotless. Why? Is there something wrong? the ski ran flawless and had no problems.

 

[Crab]

Not that simple, the small pin and big pin cases are different, the cylinders are different also. You can put a small pin cylinder on a big pin case, but not reccomended by group K, and vice versa. They made like 5 different 750 heads, with different CC's depending on model and year. The small and big cranks use different pistons, due to the pin size. The PTO thread size is different on the 2 cranks as well. I use 650 electrics on mine as its simpler and mostly reliable, the 750 electrics seem to go wacky for no reason, but there are A/M ignitions that will work with them including enhancers or Advent. When they came out with the SXR, they kept the big pin design, added more CC, but lowered port timings that the SXIpro had and beefed up the cases, however I still like my small pin for the great bottom end and under 7000 rpm.

 

[sflsurfrider]

why cant kawi just be like yami?!?!?!

 

[Scorn800]

Big pin is 22mm wrist pins- small is 20mm
all 750 flywheels are the same except i believe 92sx. I was told different taper.
750 electric's are better. Digital CDI & on 04 sxr's DC CDI
750 stator's are know to go bad

 

[john zigler]

Big pin is 22mm wrist pins- small is 20mm
all 750 flywheels are the same except i believe 92sx. I was told different taper.
750 electric's are better. Digital CDI & on 04 sxr's DC CDI
750 stator's are know to go bad

the way i remember it, the small pin, and big pin cranks had different tapers on the flywheel end.

electrics are different between the two motors as well. stator coil assy timing is different to match the different motors. CDI's have different timming curves, and rev limits to match different motors.

the early 750 stator's had week grounds, and are known for going bad.

crab said it pretty good. don't forget the 750 small pin piston's have a posrtion of the piston skirt cut higher, and the big pin pistons do not have this.

also, ( again the way i remember it) the later small pin motors, have the same larger PTO threads, so you cannot go by this alone.

i have heard of guys running the big pin lower with a small pin cyl, and i though it was supposed to work well. ( again going by memory). i have a friend who is redoing his big pin 750 X-2 as we speak, and i know he is going to build his motor like this, so i guess we'll see. basically he is going to cut his piston's like the small pin ones, and run a small pin cyl.


ski crazy;
what color is your motor? a 96 750 should be green. if yours is silver, someone may have changed your motor. you have an aftermarket intake and lots of other bolt ons. like i said earlier, a big pin motor has 12 intake stud holes.

the debate between the two motors has gone on for a long time.

basically, the "big pin" has a "stronger" bottom end, and crank. it has taller port timming, which leads to making more hp in the upper RPM's. these were kind a "turd" on the low end, but pulled hard up high. good for racing, poor for freestyle.

the "small pin" motors have lower port timming, and make MUCH more power on the bottom end. but, they have a weaker crank, and bottom end. ( not that this can't be fixed up). these make much better free style motors, and generally are funner to ride.

zig

 

[john zigler]

why cant kawi just be like yami?!?!?!

charlie, i honestly laughed out loud when i read this. i have worked on may yamaha's over the years, but i have NOT had the chance to do alot of interchangeing of parts, ski's, motors, ect. everything i have done here in the shop is simply replace, rebuild, repair, ect, so i do NOT claim to be a yami expert by any means.

personally, i consider myself a kawi guy, just because that's what i have always had. back in the day, when we started jetskiing, that's all there was. i have always just stayed with kawis. i started with an 82 550, went to an 89 550, then put a 750 motor in it, then went to a 750SX, then a SXi pro, and now SXR's. (not that i don't like the SJ's, infact, i think i want a round nose).

anyway, long story short, i think that same thing whenever we are messing with yamaha parts, 61X, 62T, 62T cases, with 61X cyls, ect. man, just the different mid shaft bearing assemblies alone confuse me. so to me, i always think, "why can't yamaha be more like kawi?"

now after all this typing / reading about the kawi's, i could see how someone could be confused. i just guess i never think about it, and it is more of what you know, and are comfortable with.


zig.

 

[djkorn1]

Zig, you took the words out of my mouth with the Kawi/Yam thing.

At least Kawi motors have been updated after 1996. Thats why a stock SXR blows a stock SJ out of the water.

*Flywheels: Different taper for big/small pin (not interchangable)
*Cases: Big pin can be used on small pin, but not the other way around unless you grind the hell out of em.
*Cyllinders are interchangeable, but have different porting
*Heads are interchangable but all have different cc's, so different psi.
*Pistons are not interchangeable due to pin size.

BTW:

Small pin 750 motors: Better low end hit
Big pin 750 motors: Tough to get low end out of them
Big pin SXR motors: Hit WAYYY harder on top and bottom. (must be the porting and extra cc. Maybe diff electronics too.

 

[Scorn800]

The 750 flywheel's are all the same from 93 & up. I know I've tried them.
All 750 stator's will work with 03 and under cdi's. I know I've tried them.

 

[dbrutherford]

A few things i can add.

I once had a 92 750 SS engine I put in a 650SX. Well the 92 750's had a "bastardized" crank as RAD told me. Supposedly they used 650 rods that a different size pin size. Can't fully remember the details but just that they couldn't rebuilt them because there weren't rods available.

Another note about the early snall pin 750's were that they had the through the cases hole for 650 style stator wires. They just used a little plug that was screwed in place. On later big pin engines this was never machined. So to run 650 electrics, you have to drill the center hole out, then also drill/tap the two screw holes. All 650 cases had this done from the factory.

I think I am going to buy a set of 800 SXR cases & cylinder from Kawie. If I can get them at the dealer's cost then I will be making out. Then just buy a Hot Rods crank, Pro-X pistons, ADA head, R&D intake... ect and build up the engine. Otherwise I plan to buy an 800 SXR just to pull the engine, pump and electrics out of it. I just can't seem to find a decent 750 engine that won't need a bunch of $$ to fix. Plus crank rebuilds are expensive and you can't buy a new small pin crank.

 

[Crab]

If I do another, I may go 800 and drop the cylinder right down on the cases like my current motor, no base gasket only 1211.

 

[Scorn800]

If I do another, I may go 800 and drop the cylinder right down on the cases like my current motor, no base gasket only 1211.

Hey that's a stock class secret. shh. shh, shh:sneaky:

 

[Scorn800]

I'm with dbuherford
I've been told 92 750 cranks were odd balls. I was told it has the same flywheel taper as a 650 crank. I've never owned 1 so I don't know for sure.