Hey all, ive hit a wall with this machine. 1996 GSX 787. It would run pretty good but idle low in the water at about 1K RPM. Wide ipen around 7K. but intermittently would bog and die and sometimes take a very long time to restart. So I replaced the old grey lines apart from the 2 directly on the carbs, but did make sure they were clean and clear. Removed, cleaned and installed both rave valves. and cleaned both carbs and reinstalled back on the ski. I did not mess with any linkage adjustments, idle screw, or high and low speed screws. Took it to the water and got it running but wouldn’t do more than idle or it would die. After a while it became harder and harder to get it going until it just wouldn’t start at all. Killed the battery trying. Got it home, disconnected and charged the battery. It starts with choke and gas well enough Then idles but both in and out of the water it dies with even a tiny amount of throttle movement. I checked the low speed screws on both carbs, they were 2 turns out, I turned them both in 3/4 turn. Popped the tops off the high speed screws and they were both fully closed, left them at fully closed for now—-where should the high speed screws be from factory?——and noticed the idle screw wasn’t even touching the stop at rest, turned it in until the plate moved, started it and it idled at 4K on trailer with flush kit and adjusted it back until about 2500-3K. It’s got spark through both plugs. The plugs were new last year and have seen less than 12 hours of use. Still dies when you give it any amount of throttle. Carb sync issue? Needle tab(s) bent? Weak spark? Timing issue?
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1996 GSX dies under any load
- Thread starter Niro
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noviceskier
Active Member
Carbs should've been rebuilt rather than cleaned, go through them with genuine mikuni kits, follow the sticky on the thread to the tee. While you're going through the fuel system, now'd be the time to replace the fuel selector valve and fuel filter too in my opinion.
the carbs were assembled with all new gaskets, internal filters and 0-rings as well as the clear plastic deals
noviceskier
Active Member
Which kit did you use?
couldnt say my father-in-law ordered the kits per recommendation from a friend thats worked on seadoo's since the 90's. everything matched up. the mylar pieces were clear as they should be. i have checked out the carb rebuild sticky. as far as assembling the carbs go, all i can think of is that the needle tab got bent and its flooding? or a piece of junk from the old gray lines plugged something up immediately upon first startup? im under the impression that the linkage adjustment can stay the same since it ran well enough before i tore the carbs down.
can you please elaborate? the mylars were clear and the diaphrams have the red studs. for arguments sake lets just say they for sure were mikuni, i cleaned and assembled the carbs per the sticky, what possible reasons are there that would cause it to hard start, and die when given any throttle?
Unfortunately the clear mylars and red stud are no longer proof it is Genuine Mikuni.
Hard start and stalling with throttle could be plugged transition circuits, leaking needles and seats, diaphragm too stiff, wrong spring, air leaks, etc........
Without going back to basics and verifying parts are Genuine Mikuni we are just guessing.
Unless the parts were in the actual Mikuni package or bought individually from someone trusted like OSD or Westside Powersports then there is a very high chance they are not Genuine.
Hard start and stalling with throttle could be plugged transition circuits, leaking needles and seats, diaphragm too stiff, wrong spring, air leaks, etc........
Without going back to basics and verifying parts are Genuine Mikuni we are just guessing.
Unless the parts were in the actual Mikuni package or bought individually from someone trusted like OSD or Westside Powersports then there is a very high chance they are not Genuine.
GGuillot
Well-Known Member
Ditto on all the recommendations above. I have a 96' GSX, if you do the carbs in detail, rebuild with genuine oem kits, sync everything, adjust everything, stock needle settings it will/should run fine. If steps are skipped (no pop off ck), non genuine kits, skipping new oem needle/seats, and a partial effort is put into the carbs, you'll get problems and be right back at pulling them off again.
Details count, take your time, there's very little room for error and doubt with the carbs. If it's right, you'll be rewarded with trouble free riding for yrs to come.
Not a good assumption, you need to readjust everything, and ck the oil and choke cables while you're at it.
Details count, take your time, there's very little room for error and doubt with the carbs. If it's right, you'll be rewarded with trouble free riding for yrs to come.
Not a good assumption, you need to readjust everything, and ck the oil and choke cables while you're at it.
Mikuni carb kit installed, pop it test on both carbs is about 32-35, Cables all adjusted, low speed 1 turn out and high speed closed. she starts good, idles at 1500RPM in the water and still falls on its face if you gun it, or try to go past 3K RPM. an improvement from before when it would die with any throttle at all. After a while at 3K you can very slowly get it up to 4K and once she hits 4500 it’s like you flipped a switch and she goes like crazy. If you stay at or above 4500 it’s got immediate response and fast acceleration. With the throttle pinned it “hunts” or surges a little between 5500 and 6500(maybe adjusted throttle cable a bit too tight?)
After running it 20 minutes or so in the water I started to play with the low speed screws 1/4 turn at a time both in and out and turned the rave valves in a full turn, no change on the low end issue.
After running it 20 minutes or so in the water I started to play with the low speed screws 1/4 turn at a time both in and out and turned the rave valves in a full turn, no change on the low end issue.
GGuillot
Well-Known Member
1 turn out on the lows is good, but it sounds lean, and I don't think it would fix your mid level transition, but I don't have the HS needles completely closed on either of my 787 skis. I run them at 1/8 to 1/4 out....but that's me.
Next, I'd do a fuel bypass of the fuel selector and fuel strainer under the steering, narrow it down and see if you have an air leak getting in the fuel line to the carbs.
Next, I'd do a fuel bypass of the fuel selector and fuel strainer under the steering, narrow it down and see if you have an air leak getting in the fuel line to the carbs.
I did the bypass with the ends zip tied and went straight from the “on” outlet of the baffle to the mag carb. No change. I tried the HS 1/8, 1/4, and 1/2 turns out. Each HS adjustment I tried the LS at 1 1/4-2 turns out in 1/4 turn increments. Still no change. None of this was in the water just on the trailer with flush kit.
dr00andrew
Well-Known Member
did you spray carb cleaner into the pilot jet and watch it come out 3 little holes in the carb barrell? if you are struggling in the off idle-4k rpms or so, those holes may be clogged up and you are not getting good fuel flow to your engine in that range.
GGuillot
Well-Known Member
Your chasing your tail if you can't confirm the carbs were rebuilt with genuine oem kits, which run about $125 for a dual carb setup. 'Mikuni' kit means nothing, where were they purchased from?
The 4 little holes need to be flowing well, should have been sprayed out with brake or carb cleaner and highly compressed air. Repeat this several times. The pilot and main jets should be removed and blown out.
You can't half ass on the carbs, they need to be perfect. Your problem still points to carb issues.
The 4 little holes need to be flowing well, should have been sprayed out with brake or carb cleaner and highly compressed air. Repeat this several times. The pilot and main jets should be removed and blown out.
You can't half ass on the carbs, they need to be perfect. Your problem still points to carb issues.
As I said, the original Mikuni kits were ordered and installed. The holes were thoroughly cleaned and blown out with my compressor. Tail chasing I am not. And the kits were about $50 each plus shipping. To repeat. OEM kits were used. Carbs were thoroughly cleaned and blown dry. All per the sticky. It’s all fresh gas with new black fuel line.
Not trying to tune it in, just figure out why it’s starving of fuel and dies mid range
dr00andrew
Well-Known Member
there could be an air leak of some sort in your fuel system. did you replace the fuel selector switch and the o-ring and strainer in the fuel/water separator? when you buy a used sea-doo you have to re-do the entire fuel system and that means every single thing that fuel passed through. If possible, send a link to the site of where you bought the carb kits from.
i also didnt see anywhere on this post that you replaced your float needle and seats. thats a critical step of carb rebuilding. you should have new1.5 needles and seats in there
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