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Discussion Starter · #1 ·
I have a 1999 Kawasaki STX 1100. I noticed during disassembly & cleaning that after I removed the needle & seat in all 3 carburetors that the front carb did not have an orifice/nozzle under the seat while the middle & rear carb did. Is this factory normal ??? The carb is the furthest from the fuel pump.
 

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That is a return line jet. Watercraft use a fuel line that "returns" fuel back
to the fuel tank only at an ~idle. If there was no return line, the fuel pressure will
cause the engine to run rich at an idle. After the idle, and as rpm increases,
the return line is less effective because the engine is consuming nearly all
the fuel from the fuel pump.

On carb racks with only one fuel pump, it is common for the carb closest
to the pump to have no return line jet. In this configuration, only the last carb
needs the return line jet.

Fuel comes into the fuel pump and is pressurized, and supplied to the nearest
needle and seat. The fuel is then supplied to the next needle and seat through
a passage way or connecting hose, and the process can repeat until the last
carb (where the return line (hose) attaches to the carb). The last carb will
have the return line jet. This configuration supplies the same pressure to
all carbs.

If there is no return line jet, and fuel is allowed to flow back to the fuel tank;
there is no fuel pressure, and the engine does not start.

Look at your carb rack, fuel should enter the fuel pump and then be distributed
in series (1, 2, 3) and then restricted and returned. Either there is a logical supply
and return network, or a restrictor is missing, or the carb rack was disassembled,
and reassembled in the wrong order.


Bill M.

Sorry I can't do better, I have not worked on stx since ~2005. But all the CV
carbs for the 1100 had problems starting after sitting for a week or so. Many
were always hard to start.
 

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Discussion Starter · #5 ·
I rebuilt all the carbs. The carb furthest (front of jetski) from the fuel pump is the one without the restriction.They don't look like they were ever disassembled from the original configuration. In any case if I install them and find that I have a problem can I install a restriction in the return hose. If I can what size orifice should I start with (like a .030)?
If the carb is missing the part I'll probably never find one !!!😂
 

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A 30 to 40 (.3mm to .4mm)(.012" to .016") pilot jet is closer to normal
for a Kawasaki. .

Yamaha uses a .5mm return line orifice, and Sea-Doo uses a large
.6mm return line.

But Sea-Doo runs really rich pilot circuits, so they need a larger return
line orifice to reduce the tendency of loading up in a 5mph zone.

A 35 to 40 pilot jet from a motorcycle carb should get you close.

We used to use 30 to 35 pilot jets from a Mikuni VM round slide
carb for old 440 and 550's.


Bill M.
 

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Or if you had a set of #61 thru #80 drill bits, you could measure the
hole. Convert to mm's (and keep in mind .35mm is a 35 pilot jet)
and purchase the appropriate sized pilot jet from a motorcycle.
Maybe Yamaha or Suzuki. Honda used to have a bunch of weird
carbs, and Kawasaki used other brands after1980.

But Chinese replacement parts should work fine.

Bill M.
 

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Discussion Starter · #8 ·
Thanks for your help. I have the carbs all back together and will keep this info in mind. I upgraded the slow jet #50 with a 1/4 turn out as prescribed by Shade Tree. I was looking at the fuel and return lines and it looks as if it might feed the carb furthest from the pump(front of jet ski) first and flow back toward the pump to the other 2 carbs and drop through the existing orifice to the return line.If it does my problem is solved . Its difficult to chase the internal lines with the carbs back together. I guess I'll find out when I reinstall them in spring.
Thanks for your help and incite. By the way don't buy from Marine Parts Guys it's a scam website !! I got burned for $20..
 

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The most common problem with all the Keihin carbs (CV or Normal) is hard starting
when cold (after sitting for a week. The engine should start within 1 minute using the
choke.

A simple fix for most people is making their own .040" thick carb base gaskets. I have
a how to and sheet gasket part #'s if you need it later on.

If you disassembled the rack, there is a procedure for decreasing the possibility of
making a hard starting.

A fuel primer is an easy way to help it start when cold, but it doesn't actually fix the
problems cause. In the future the problem may cause the engine to die while idling
(at a normal Kawasaki low idle rpm.


Good Luck.

Bill M.
 

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Sorry I have not posted it yet. I am in the process of editing several
versions into one document.

Bill M.

The choke is more reliable, and there is a starting procedure that
works for all carburated watercraft.
 
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