300/440/550 I purchased a JS300

[ib456]

Hi,

I just brought a JS300 (I believe), havent picked it up yet, but the hull is in good shape but it is missing the carb, jet unit and intake grate.

Now it only cost $150nzd so not much. It will be a project once i finish my motorbike.

If anyone knows does the 440 jet unit fit into the 300 or will i need to find one from a 300. as for the carb and intake grate i should be able to find those without too much trouble, but the jet i am a little more unsure of.
Are there any good info sites for the 300 as well? i have had a look but not found a great deal.. tho half the fun with stuff is working out how it goes and getting it running without a manual.

thanks

stuart

 

[Polish jet pilot]

Jet pump could be adapted from a 440 or 550. They differ in type of flow however. To be honest, think of swapping a 650 in there. Otherwise the power isn't there...

 

[WFO Speedracer]

440 pump is a direct swap,440 props are also the correct pitch for that and you can put a 38mm carb on it instead of the stock 34.

 

[restosud]

on pwctoday.com there's jetskiheaven who has a 300 js kerker or mariner pipe he might sell.that would be a nice addition to this boat along with a 440 pump and 15* impeller and the 38mm carb per wedo.

 

[ib456]

Thanks guys,

Thats good to know, as for a 650 transplant, they cost a huge amount here so it would be a waste of time doing that, would be better off just buying a 650 complete and ditch the 300. But as it is something i have always wanted and the fun part will be putting it back together and get it working if i can.. i will try to find a 38mm carb rather than the 34. As for the jet unit, will see what i can find, sounds like the 440 is the better pump to try and find.

Would the 550 pump fit in or would it just be a waste of time due to it being meant for a 550? If it would need an adapter plate that is no problem, can deal with that and there is a 550 pump for sale not far from where i live.


the hunt for parts will start shortly.

thanks

 

[orangefinger]

before you start any work please consider following things...

- What is your weight ? That 300 will be good for kids not for an adult
- Engine Motormounts are for a single 300cc engine, you will have to modify if you drop in anything bigger >> Add addtional engine mounts..

My strong advise...sell it !

 

[restosud]

550 pump will bolt up but you'll need the 550 driveshaft as well.get a 440 pump as they are better.
you can find 440/550 motors for little $$$$ also and drop one in.
i can hook you up with a complete 440 and electrics for $200 plus shipping.

 

[Motorheads5]

before you start any work please consider following things...

- What is your weight ? That 300 will be good for kids not for an adult
- Engine Motormounts are for a single 300cc engine, you will have to modify if you drop in anything bigger >> Add addtional engine mounts..

My strong advise...sell it !

I totally agree and as for a 440 pump they are total old school junk, bulkhead issues , no taper,hassle to change impeller's ect ect.

 

[Lakeman]

Don't waist your time or any more money on this ski. You will end up with $500 junk bucket that no body will want to buy.

 

[Crab]

Don't waist your time or any more money on this ski. You will end up with $500 junk bucket that no body will want to buy.

Best advise I have heard yet.:lmao:

 

[ib456]

550 pump will bolt up but you'll need the 550 driveshaft as well.get a 440 pump as they are better.
you can find 440/550 motors for little $$$$ also and drop one in.
i can hook you up with a complete 440 and electrics for $200 plus shipping.

Thanks for the offer but the cost of shipping would be at least $200 to get to New Zealand I would think. I will keep an eye out for a 440 pump and driveshaft, like i have mentioned its only a project to keep me entertained. If it goes and i keep it i might try to find a bigger motor for it at a later stage or if i manage to find one in New Zealand.

thanks

 

[ib456]

Well I have found the parts i am missing closer than the US so cheaper to ship, still havent picked the jet ski up yet but doing that this weekend, so will get it running as a 300. I have a 550 lined up for it as well, but wont do that until later, will get the motor but not put it in until i get a bit more room inthe garage.
So all up it shouldnt cost more than $465NZD.. which isnt much considering that the NZ dollar is only worth 62cents US at the moment...
filthy exchange rate..

 

[Motorheads5]

well that is good you are finding part's for the project. don't get discouraged from negative comment's about your 300 you might have alot of fun with it and I hope you do get it running and have alot of fun with it. one thing to keep in mind most of the guy's on this site are hardcore standup rider's and a js 300 is not a desirable ski for any of them. however that does not meen they will not be here to help you. good luck with the project I have about 6 js 550's. lol

 

[ArtMaybee]

Ok, I've seen the comments about the ski being junk. Although it's definitely not the most modern ski they can be fun. This is the Old School section of the forum after all.

The js300 hull is the exact same hull as the 440/550. The mounts in a js300 hull are the same. The differences are in the motor mounts/plates on the engines.

The 300 doesn't put out much power but comparing stock to stock in put out like 3hp more than the 440 did. You won't win any races with it and it takes longer to get the hull to plane out. It's still a fun ski if you've never ridden anything more powerful.

You can build this ski and have next to nothing invested in it. My first ski was a js300. I rode it twice with the 300 engine in it. It was a bit low on compression so not much power at all. I bought a somewhat beat up 550 for very little that had many mods and aftermarket parts (aluminum pole, pipe, prop, high compression head, etc.) I put the 550 parts on the 300 hull and had a very fun ski. The nice thing about js300s is they don't tend to be ridden as hard. Most of them I've seen were in really nice condition.

The thing about the old js skis... They are a bit more work to ride than the newer skis. And if you get good on a js, it will translate well to the newer larger models.

People who have spent some time on the older js skis usually remember them fondly.
a modded 550 can be a handful. After building my superjet, i can say that no, the 550 was nowhere near as fast as the SJ. But at the time... I had a LOT of fun for very little money.

I bought the js300 for like $150 and the well used and modded 550 for $200.
I had a ski that was a BLAST to ride for $350 plus my labor to put it together?
After I moved up to newer skis, i parted the 550 out made quite a bit more money than I'd spent on it.

I've had a js440s, a couple js550s, modded 650SXs, modded 750sxi, a few modded superjets. I had as much fun on the that first 550 as I've had on any of my skis.

We've all got to remember that not everyone has the money to invest thousands into a ski. But those same people can still have fun with a small investment.

 

[ib456]

I picked it up on the weekend, isnt too bad, dirty and needs a good clean, turns out i have about 1 1/2 motors which maybe handy, couple of starter motors and a pile of other bits and pieces.
It wont be fast but it is only something to learn the basic's of how they work and go together. I have a few friends that should be able to ride it in the 300 form.. but will get a 550 for it.
I have told my girlfriend she has to put it back together as it is all in parts, i will clean all the oil out but she has to mount the engine and do the wiring. Really simple from what i can tell, but it may stop her from pointing out that I shouldnt have spent the money as i have too many toys already.

Sould be a bit of fun anyway, at least my painting ability will get tested again and it is improving.

 

[Jawbreaker]

If your curious...

js300 = 31 hp

js440 = 27 hp (yes, it's less than the 300.)

js550 = 48 hp (I'm pretty sure)

650sx = 51 hp

 

[Polish jet pilot]

I'd say if you have some cash build a monster 300. Full exhaust, new reeds (yes it has them), port the cylinder, aftermarket head if you can find one, blueprinted pump and good prop, fs cone for bottom end or tune the pump for speed. Concentrate only on engine and pumpAnd see how it rides! Tubbies add great cornering ability and plane the ski faster - consider... I guess you are looking at about about 700 USD

 

[WFO Speedracer]

I wouldn't do any internal mods to a 300,bolt ons are ok,the starter clutches are weak and if you start porting and bumping compression the starter clutch will give you fits,build it ride it and when you want something bigger and faster sell it and buy something else.Now if it were a 300 sx that would be a whole different ball game lol :sneaky:

 

[ArtMaybee]

For reeds you can buy a set for a 650sx and have a spare.
I think the js300 I had used the same starter and bendix as the 650sx as well. But it's been too long since i had the 300 ( I could be wrong on the starter/bendix).

The pistons are also the same as 650sx if you need to replace one. If you can't find a performance head, you might be able to send the stock on off have it cut and the dome reshaped. I've heard you don't want to shave the 300/650 heads without reshaping the domes. Though I did have a shaved one on my 650sx for a while (180lbs compression) and never had issues with it. So you might be able to get away with shaving the head a little for higher compression.

It would be interesting to see what a 300 could to with a pipe, porting, compression, better carb, and a good prop. But man would it sound funny.

some people rag on the 300/440 pump but it's all they used in race boats back in the old days. 550 modified all used 440 pumps. Though they did reinforce the bulkhead.

 

[WFO Speedracer]

Defiantly wrong on the starter & bendix,the 300 starter and bendix differs from anything else.