300/440/550 Mod a 38mm carb?

[delagem]

I'm converting a 89 JS440 to a JS550 due to finding a crack in the 440 cylinder. Figured since I needed to replace the cylinder anyways, I'd just go ahead and upgrade.

The one remaining thing I am struggling with is "rejetting" the 38mm carb. It doesn't have jets, more like a freeze plug with a hole drilled in it. I have read that GroupK and a few other shops will "modify" this carb to work with the JS550. Mostly that's drilling the hole a little bigger.

I don't wanna pay GroupK $95 to drill a hole! Does anybody know what size to drill the hole to for this swap?

 

[WFO Speedracer]

I believe we drilled them about .080".The 38 carb actually works pretty good on that ski set up properly as long as you don't have too many mods ,the 44bn is a pile don't even think of going there.

 

[D-Roc]

,the 44bn is a pile don't even think of going there.

Word!!!:biggrin:

 

[delagem]

Wow, .080! That's huge! I took the smallest drill I've got, a #60, which is .040, and it won't fit the stock hole.

 

[WFO Speedracer]

Actually unless you have it modded out it will work as is,I have an 86 with a 38 carb ,flame arrestor and a kerker pipe it works fine and the main has not been touched.

 

[delagem]

Oh, that's good to hear! I was kinda leaning that way, unless I get an exact # of how much to safely drill, I was just going to turn out the hs needle a turn and to test it. Bring some tools and pull the head after a min or 2 to check the piston wash.

 

[kurtwolff]

Hop on ebay and pick up a carb, I just saw one sell for .99 plus $6 shipping. Can't beat that! I think I might have a few around if you are interested, let me know. -Kurt

 

[delagem]

Some of you guys may know Randy from www.watcon.com He's one of the foremost Polaris guys in the country, and he has built more than a few Kawasaki racing 440 and 550's. Here's what he sent me:

Michael,
The 44mm carb is better, but the 38 is okay for now.. You will need to drill the high speed circuit out to .038” and most likely will need to update the needle and seat with the newer “Viton” tip. I have them for approx $25.00. The carb should hold approx 14lbs Pop-off pressure without leaking.

Now where the heck do I get a .038 drill?

 

[steve802cc]

I've got a brand new Mikuni 38mm SBN that I could sell you.

 

[WFO Speedracer]

I don't think that sbn will fit on his manifold without hitting the cylinder ,same deal as with the sbn 44 carb.

 

[steve802cc]

Ya good point, it would likely have to use a spacer but will still be a much nicer carb than the stock one.
Steve

 

[Mark Gomez]

Carb for sale

ive got a 38 mm carb from my 1994 550sx with the manifold and Hot products Flame arrestor the pictures are in my gallery im selling the whole kit for 75 bucks
thats a steal i bought it nearly untouched like 3 hours on the ski and i rebuilt the carb used it for a month or two before i upgraded to a 44 mikuni blackjack.

 

[D-Roc]

i switched my old 550's carb this past summer to a superjet stocker 44mm SBN, WOW!!! The ski has never ran so good, its the piston port motor and used to be a stubborn ski to start, even when warmed up, now it starts, idles, and revs smooth. i used the spacer plate and longer bolts and two studs to install it and it was worth it. http://www.northwetpowersports.com/index.php?module=pncommerce&func=itemview&ItemID=524

 

[Mark Gomez]

Carb Pics




75 bucks for the whole enchilada

 

[WFO Speedracer]

Dude I hate to be the one to burst your bubble but( POP) that won't fit his boat.He has a piston port motor,yours is a reed valve and never the twain shall meet.

 

[Mark Gomez]

i know i know im sure the carb could though im just trying to sell the thing. the pics i have are included with manafold and at 75 bucks with all of that is cheaper then the $99 carbs on ebay my boss is selling lol

 

[WFO Speedracer]

No the carb won't fit either,the bolt patterns on Kehins and Mikuni's are totally different,they did make an adaptor for this years back,I am not sure who has one now though.

 

[Mark Gomez]

aww shoot yeah it bugged me and i went out and looked at dead motor i have in the back and realized that i just excited to sell it when i saw 38mm.
yep thanks my bad