Carb tuning question for Stock Superjet 701 - Dual 38mm

[jetskee]

A few questions....I have a single 46mm Mikuni on my Kawi, so the whole
dual carb thing is new to me. I have the stock dual 38mm on my new stock
2000 superjet. It was running like crap today, and I'm not sure if it is lean
or rich. If I'm giving about 1/4 to 1/3 throttle, it runs ok. I can then go
up to about 3/4 throttle and it takes off great, but if I hold it there,
it started to bog down then almost dies. If I let off the gas and
feather the throttle a bit, it stays running and is back to normal
in a few seconds.

From idle, then pulling it to WOT, it hesitates for just a second then
goes pretty strong.

Would you say this is a lean or rich condition?

I was trying to play around with tuning and found that the adjusters between
the two carbs are damn near impossible to reach and turn effectively.
You can't get a screwdriver in there, and you can't turn them with your
fingers.

So, when I got home, I took the carbs off just to verify what jets were in them and to verify for sure where my adjuster settings were after I
messed with them.

This is what I found:
Front carb
- High adjuster : 1 turn out
- Low adjuster : 1 1/8 turn out
- High jet : 130
- Low jet : 70
- Spring : 115 gram (gold)
- Needle/Seat : not sure how to determine, but should be whatever is stock

Rear carb
- High adjuster : 1 turn out
- Low adjuster : 2 3/4 turns out
- High jet : 130
- Low jet : 70
- Spring : 115 gram (gold)
- Needle/Seat : not sure, probably whatever is stock.

I'm not sure how that one low speed adjuster got SO far out of whack
from the rest of them. I sure don't remember turning it that much.
I assume that could have contributed to my problems?

So, two things:

1. I want to put this back to factory settings, since it's a stock boat,
and proceed from there on my next ride.
I don't yet have a shop manual, so can anyone tell me what ARE the stock recommended jets/screw adjustments?

2. Any tricks to make the two adjusters between the carbs a little
more accessible for tuning when at the lake? Any cool modifications people have made ? I thought about cutting off part of a paper clip and JB
Welding it in the adjusters, so I had a T-handle on there to adjust with.
Any ideas are appreciated.
http://www.blowsion.com/detail.asp?PRODUCT_ID=01-02-891
And I know Blowsion has these replacements, but $52 freaking bucks???:bigeyes:

Thanks.

 

[Matt_E]

Yeah, those adjusters are that expensive.

IMHO, you don't need them. Stock 38's do not need to be messed with once they are tuned.

It sounds to me like your fuel filters (or lines, or reserve switch) needs to be cleaned out. What you are describing sounds like it's running out of fuel.

 

[jetskee]

1. I want to put this back to factory settings, since it's a stock boat,
and proceed from there on my next ride.
I don't yet have a shop manual, so can anyone tell me what ARE the stock recommended jets/screw adjustments?

Never mind...I found it:

For future reference, shop manual settings are :
High Jet : 130 Low Jet : 70
Front High Speed Screw : 1 1/8 (+ or - 1/4)
Rear High Speed Screw: 1 1/2 (+ or - 1/4)
Low Speed Screws(both) : 7/8 (+ or - 1/4)

 

[jetskee]

Yeah, those adjusters are that expensive.

IMHO, you don't need them. Stock 38's do not need to be messed with once they are tuned.

It sounds to me like your fuel filters (or lines, or reserve switch) needs to be cleaned out. What you are describing sounds like it's running out of fuel.

Yeah, that's what I was kinda thinking, too. The way it is acting seems
pretty drastic to just be a tuning thing. And this started all at once.
I just got it in March, and it had nearly a full tank of gas.
It was running great, then when I ran out that tank of gas and refilled it,
it started running like crap.

I thought maybe I got some bad gas, so I siphoned the tank dry and
put in some fresh gas from another station, but no change.

So, how do you check the fuel filter. I pulled it off the ski and
dumped out the gas that was in the bottom of it. It looks like a
sealed unit that you can't take apart to check.

Just looking into the ends, it doesn't look clogged or dirty.

 

[Matt_E]

There is one filter in each carb. (Maybe not on 38's...check both of them though)
Remove the square cover (fuel pump side) There should be a cylinder with black plastic rim in the carb body. Pull that out and clean.

 

[Gainera2582]

I use a dime to adjust my highs on my 38s. Works like a charm.

 

[freestylegeek]

Skee,
I went through the hassle of drilling my adjuster screws, and pressing roll-pins into them. It worked great, but man was it a hassle! The next best thing is a looooooong shaft, 3/16 small flat head screwdriver (craftsman #41248 Q PR). You end up going in at a 30 deg. angle, but you CAN get to the inner adjustment screws. The screwdriver is too long to use on the 'outer' screws, but you shouldn't have any trouble reaching those with a standard flat head screwdriver.

Also, with those stock carb settings (115g spring and 1.5 n/s = 55psi) make sure you leave all three screens in the flame arresters. If you end up pulling out two of them, you'll probably have to drop to a 95g spring to eliminate your hesitation.

 

[jetskee]

The dime sounds like a darn good idea....never thought of that, plus it's easy to carry around.

BTW, I found my problem....you guys are gonna love this one....

The one-way valve on the gas tank that allows air to flow in but still keeps the tank pressurized.....it was backwards.....

So, the harder I rode, the more suction got created in the tank (since no new air could flow in) and eventually it got to the point that the engine couldn't overcome the suction and I ran out of gas.

Flipped that around the right way, and things are now fine.

It was a problem all along, but since the tank was mostly empty on the first ride, and I didn't do much WOT running, I don't think I ever got the suction in the tank so bad that it stopped the flow of fuel.

When I refilled the tank fully with gas, and the air pocket in the tank was smaller and compressed more quickly, the problem became apparent and
caused the stalling out during a WOT run that I was seeing.

I took the ski out today, got the carbs tuned pretty good, and I'm happy now!
:arms:

 

[Jumper]

If the dime will fit you could JB Weld that in. Instant easy adjuster.

 

[Matt_E]

If the dime will fit you could JB Weld that in. Instant easy adjuster.

It will come off, it's only a matter of time. :arms:

Besides, there is no need to constantly adjust those carbs. Is there? :dunno:

 

[2lick]

i kinda went throught that last year.... i had clear fuel lines what it turned out to be was lack of fuel when it was trying to suck a lot at hight rpm... when i primer mylines i still had bubbles in them..... so it wsnt getting a full line of gas when it needed it....

maybe this helps?

 

[jetskee]

i kinda went throught that last year.... i had clear fuel lines what it turned out to be was lack of fuel when it was trying to suck a lot at hight rpm... when i primer mylines i still had bubbles in them..... so it wsnt getting a full line of gas when it needed it....

maybe this helps?

Thanks for the suggestion...but I already found the problem (see my previous post).

The one-way valve on the gas tank that allows air to flow in but still keeps the tank pressurized.....it was backwards.....

 

[Vumad]

Never mind...I found it:

For future reference, shop manual settings are :
High Jet : 130 Low Jet : 70
Front High Speed Screw : 1 1/8 (+ or - 1/4)
Rear High Speed Screw: 1 1/2 (+ or - 1/4)
Low Speed Screws(both) : 7/8 (+ or - 1/4)

I know I'm bumping a very old thread. I just found this thread on google.

I just rebuilt my carbs and removed the brass screw covers (newer sj have screws blocked) and replaced them with t-screws from jet maniac.

My ski would not even run with those screw settings. It would just sputter and die and never grt going. My stock screws were closer to that but the new screws aren't close to that.

I'm still trying to get it dialed in, but I'm pretty close right now with both lows at 1.75 and the highs at front 1.5 rear 2.0. Not exactly that but pretty close. Anything less my plugs were turning out white.

If you don't remember what your screws are, or if you replace the screws, don't go by the stock screw settings.

 

[Collussus]

ancient thread update 2020

bone stock 96 SJ, only mod is chokes removed - primer
Same as Vumad. My 1996 SJ shop manual confirms the above settings.

Also, the ski runs like crap on them. I arrived at the 1 1/2 low and 1 1/2 front and 1 7/8 rear by beachside screwdriver time. Pretty close to above.