300/440/550 550/750 conversion ?

[screaming440]

i am working on the 550 conversion and got a few questions.

i got the motor sitting in the ski on the 550 bed and JRE convertion plate.
it is sitting back with the motor mount holes covered by about an inch of the bed. is this normal or do i need to change something to get it to fit?

also what do i need to hookup the throttle cable?


Thanks

 

[Motorheads5]

ok well did you read much about how to do a conversion before you started ?
first of all you need to run the 550 drive coupler it is longer and that will allow you to align the bed plate holes with the motor mount's.
I suggest you go to pwctoday.com and study laserman's build thread's that's what I was able to do and that guy really is a wealth of knowledge on this issue and I would like to say do alot of searching and reading in the vintage section if needed send me a pm and I can help you . good luck. you will love the ski.

 

[screaming440]

yeah i been reading a lot but i just didn't understand the coupler thing.

i guess the reason i was having trouble understanding this is that the motors i have have press fit couplers that would not work on a 750 but last night i looked around and found that one of the motors i have has a threaded coupler.

 

[Crab]

550 coupler is longer

 

[tnj4life]

I had to switch my throttle cable on my 440/750 conversion from the stock straight cable to a 650sx or 750sx throttle cable which has the ball on the end of it for the carb. The 440/550 cable is a straight end. A sj cable may work as well.

 

[jetsport484]

Hey there Screaming, If you could keep us posted on what issues you run into. As I plan on doing this project Myself come Jan after Daytona, Looks like a fun build and the bennifits should be awesome! Good Luck!!




Hey crab your lookin better today. Looks like your up and walkin again.

 

[Conquistador]

If the 550 coupler doesn't directly fit on your 750 (didn't on my big pin), then you will have to bore & re tap the coupler. That's what I did & it's been great so far.

the throttle cable bracket is a pain & I was reminded of that this weekend when I broke my cable. I'll get pics when I can, but it may take a while as I don't have a camera readily available.

 

[screaming440]

thanks guys for the input.

i am still not sure what i need for a throttle cable. i called a dealer and they told me there are 4 different cables for a 750 sx.

anyone know difference between the 4 cables the dealer has listed?

tnj4life are you using a 1 or 2 carb motor?

as far as this build is going i am lerning there is a lot more to it than i understood when i started. there is a bunch of bits and pieces info around but a lot of it you must read between the lines to understand.

so for anyone reading that may be starting this project i will try and summarize what i have learned.

so far what i have learned as far as the coupler goes you must use a threaded 550 coupler on the 750 or the motor will sit back too far. The instructions i recieved with the bed plate said to use a 440/550 coupler. however, a lot of the old 440s have press fit couplers that will not work. i allso found out that the 550 coupler fits the small pin 750 but the big pin motor has a larger shaft. to make the coupler fit the big pin motor the coupler has to be machined.

 

[Conquistador]

you're on the right track!

I'm using a 550 throttle cable. no complaints here. Mine broke b/c I bent it instead of replacing it when it needed to be. I have no one to blame but myself, but I'd do it again if it last as long as this one has since I screwed it up. :icon16:
EDIT: after reading one of your previous posts, I noticed that your 440 cable is different than the 550 one. I have a 94 550 & it has the ball on the end for the carb.

Also, I recommend single carb. A dual carb motor simply won't fit. if you run duals, you'd have to remove the carbs & intake manifold just to remove/replace the battery. On top of that, I have to remove the battery just to get to anything behind the motor anyway b/c it takes up so much more room than the 550 motor. Single carb is simpler to troubleshoot also imho.

BTW the 550 coupler WILL fit a small pin 750. The small pin shaft is 19mm & the big pin is 22mm.

 

[screaming440]

yeah the old 38mm carbs used a cable without an end on them. the 38mm was used on a 550 till about 86. this is an 83 my friend got when it was new and we did a bunch of mods to it years ago. The 38mm whas replaced with a 44mm as was the cable.

so the cable has the right end on it but the problem i have is the sleve end on the cable is curved and i need one with a straight end.

 

[screaming440]

yeah that kinda sucks that the battery wont come out without removing the motor (and good to know. thanks!) but i can take the motor out of one of these in my sleep so i am still going with the twin carbs.

i was a the lake this weekend and took a look at the throttle cable on my 750sx. it has the same curved end on the cable housing that my 550 has.

anyone have a two carb 750 stand up they can look at and tell me what the cable looks like?

 

[Conquistador]

yeah that kinda sucks that the battery wont come out without removing the motor (and good to know. thanks!) but i can take the motor out of one of these in my sleep so i am still going with the twin carbs.

i was a the lake this weekend and took a look at the throttle cable on my 750sx. it has the same curved end on the cable housing that my 550 has.

anyone have a two carb 750 stand up they can look at and tell me what the cable looks like?

the 550 cable should work fine. that's what I'm running.

 

[Motorheads5]

How's thing's going on the build ?

 

[tnj4life]

thanks guys for the input.

i am still not sure what i need for a throttle cable. i called a dealer and they told me there are 4 different cables for a 750 sx.

anyone know difference between the 4 cables the dealer has listed?

tnj4life are you using a 1 or 2 carb motor?

as far as this build is going i am lerning there is a lot more to it than i understood when i started. there is a bunch of bits and pieces info around but a lot of it you must read between the lines to understand.

so for anyone reading that may be starting this project i will try and summarize what i have learned.

so far what i have learned as far as the coupler goes you must use a threaded 550 coupler on the 750 or the motor will sit back too far. The instructions i recieved with the bed plate said to use a 440/550 coupler. however, a lot of the old 440s have press fit couplers that will not work. i allso found out that the 550 coupler fits the small pin 750 but the big pin motor has a larger shaft. to make the coupler fit the big pin motor the coupler has to be machined.

My 750sx cable is a bent one on the end. Im running a single carb and the cable mounts to the manifold bracket, works great.

 

[Midlake Crisis]

For those who have completed this kind of deal, how does a 550 with a 750 in it perform compared to a 701 in a Superjet?

 

[orangefinger]

what pump ? what pitch impeller ? that would be my question if any...

 

[tnj4life]

My conversion ski was my first ski. It started as a 84 440, but that didnt last long. It runs MUCH better than a 440 or 550, much more power all around. I have a 550 pump with a 17 jetlyne impeller. The ski is very squirrly, slides alot. I haven't even upgraded my intake grate or ride plate, my grate is center cut though. I need an extended plate and scoop grate. You have to get down as low as possible to keep your balance while running wot or you'll eat it. I also have a 90 sn sj and a 94 fx1. I havent ridden the fx1 enough to compare, but its a bit unfair to compare the js to my sn cause the sn has a pipe, milled head, and a 701! My 750 is bone stock and a little low on the compression. I do know that theres no comparison on low end compared to the sj. My sj stretchs my arms like gumby:Banane09:. The js doesnt jump out till a little later in the powerband, thats kawis for you, the 701 is right off idle. The conversion ski is a much better jumper though if you time the power band right, its much lighter. Its alot like a fx1 with a little less hit. I still love my conversion ski, its what got me started in this mess! They are a great ski for someone on a budget. You could build a stock one for less than $800 if you shop around.

 

[tnj4life]

Heres a pic of the ski. Yes, its got eyes. My wife loves this ski. Its a great flatwater ski. My sn kills it bottom to top in power. Very flickable.

 

[BlueBreadTruck]

i did a 650 swap in mine. its great, but the real limit is the pump. you simply wont get great low end like a 144 or 140 mm pump in other skis!

 

[screaming440]

sorry i hadn't updated. i am kinda at a stand still till i get the parts i need.

i am still stuck on the throttle cable. i got an sx cable and like my 550 cable it is about 1/2 inch too short. it is the cable it self not the housing that is too short.

i attached some pics of what i have. the cable housing in the pic with the straight end is off the XI the motor came from. it has the end i need but its housing is too short.