Js550 Carb/Tuning Help

Joined
May 15, 2018
Likes
3
Location
Rhode Island
#1
Trying to figure out how to setup my carbs.

Been working on this budget js550 that I got for $180 and I just rebuilt the top end/did a bunch of stuff to the ski including paint/turf/new throttle etc. Right now she runs off of starter fluid but not off of gas. I've got the left nozzle hooked up to an empty slot on the gas tank and the middle one hooked up to the reserve slot on the gas tank with an inline fuel filter in the line.

Not sure what this extra nozzle on the right side of the carb is? is that return or something?

Pretty sure this carb is a bn44 right?

InkedIMG_20180515_164244_LI.jpg

IMG_20180515_164240.jpg

Here's what she looks like now.


IMG_20180515_164356.jpg

IMG_20180515_164402.jpg
 
Joined
Jun 28, 2017
Likes
7
Location
Michigan
#2
Yes its an bn 44 carb, stock on all 440 and 550's, I believe.

There is an extra inlet nozzle for the bn's for a rev limiter input. Hard to tell from pic's but it kind of looks like it's been removed. If it was there it's bolted to the side of the hull under the mount for the stock fuel filter, which also appears to be removed.

You should have a pulse line, fuel in line, return line (restricted if no rev limiter), and a rev limiter in (which can be capped if you don't want it or have it).

The rev limiter is done by tripping a solenoid based on a a voltage level at high rpms. The solenoid opens and lets fuel back into the carb inlet from the return line causing the ski to bog down.

 
Joined
Jun 28, 2017
Likes
7
Location
Michigan
#5
Yep, your right about the size being 38 instead of 44. Still operates the same with the rev limiter inlet though.

Just block it of but you’ll need to put some sort of restriction in the return line. Some people us a carb jet or others use a nylon spacer.
 
Joined
Jun 28, 2017
Likes
7
Location
Michigan
#8
The inlet should be completely capped, Its there to pump extra fuel into the carb at high rpm to bog the ski down. Rubber cap and zip tie or something. The return line needs to be restricted to .030 to keep fuel from running directly back out to the gas tank instead of into the rest of the carb. The rev limiter circuit is the restrictor before it was removed.
 
Joined
May 15, 2018
Likes
3
Location
Rhode Island
#9
Pretty sure this carbs junk. Was opening them up and it looks like there is a screw broken off at the bottom. Gas was just dripping out of the bottom instead of going to the engine.

Should i go with a different carb or stick with thebn 38?
 
Joined
Jun 28, 2017
Likes
7
Location
Michigan
#11
I think the broken stud is the least of your problems, that thing is pretty crusty in there. That thing is going to get all plugged up.

A lot of people switch to the square body sbn carb but not really nessary unless your doing engine upgrades, they are a little easier to tune for upgrades. For all stock the stock bn carb works just fine. But that carb needs a serious cleaning. I’d consider just buying a clean used one one eBay.
 
Joined
Jun 28, 2017
Likes
7
Location
Michigan
#12
Another nice thing if switching to sbn carb is no messing around with cap for rev limiter inlet or restrictor in return line. There is no extra inlet and the return line restriction is built into the carb. However you have more tinkering with jet, needle, seat and spring sizes to get it tuned properly.
 
Joined
Jan 27, 2012
Likes
29
Location
3 stacks and a rock, California
#17
You will probably break the kill switch if you drill the screws out. I would look for another? Are you doing lanyard mod??? I would only do that on a lake ski. I have been wrecked in surf because of those stupid things
 
Joined
Jun 28, 2017
Likes
7
Location
Michigan
#20
All years with stock intake manifold, there are a few aftermarket intakes with the space built in but any stock intake manifold will not have the clearance for the fuel pump of the sbn carb.
 
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