97 gtx not running over 5k rpm

[97 gtx]

someone help
Got this seadoo gtx ive been fighting to get running
Would not start at first I replaced two grounds and got it to crank but wouldn’t run right so we cleaned the gas tank and carbs put back together and would jump to 5k bog down to 4K and stall out I assumed it could’ve been the magneto which looked horrible but I just put a used one in it so I’m thinking on just ordering a new one so I know it is working properly but while I was in there I noticed only half of the grey fuel lines have been changed but there’s still some grey hose in the ski so I’m thinking there’s still trash in the fuel system.
So a new magneto and pickup coil and mikuni rebuild kit with new jets along with all new fuel lines hopefully should run fine after that but I believe the reason it isn’t running over 5k is due to improper spark or fuel mixed too Rich there is a black soot on the spark plugs but not really no oil so I’m stumped I work on cars and Diesel engines this 2 stroke is all new to me and is a budget build for the family
If anyone is familiar with these 787 engines please chime in and throw me some advice please

 

[97 gtx]

Oil pump was new but I bypassed it to pre mix the fuel
Fuel pump is new
Half the fuel lines are automotive but half are grey
Filters are new
Impeller is new
Wear ring
Plugs and ignition
Battery
New carbs
Cleaned race valves
It only has 43 hr on it but original owners never rode it second owner did but let it sit up for 2 years now I’m trying to get it back in it’s glory
Next job will be changing out the fuel petcock and all new fuel lines along with carb rebuilt and cleaning again

 

[mikidymac]

What fuel pump do you have if you haven't rebuilt the carbs?
No reason to go premix on these.

 

[97 gtx]

The carbs we’re supposed to be new when I got it so I just cleaned them I only switched to pre mix because 3 people told me to do it incase the oil pump ever give out but the oil pump was supposed to be new also

 

[97 gtx]

No idea on the fuel pump I’ll have to look back at the owners receipts to see if he had that changed too or not it’s a 787 motor

 

[mikidymac]

Those 3 people don't know Seadoos.
Every "expert" thinks oil injection is bad and will kill an engine.

The reality is the seadoo system is dead reliable and will save you a ton in oil. The only thing that fails are the little 3/32" oil lines from the pump to the manifold and should be replaced every 10 years.

 

[97 gtx]

Ok well I will take the block off plate when I get home then.
This is my first 2 stroke I’ve had I’ve always worked on 4 stroke outboards diesels and car/trucks jet ski stuff is all new to me

 

[97 gtx]

The ski fires up fine and will run but before with the old magneto it would pulse almost like jump out to 7k bog to 4-5k sputter and cut off have to choke to start back but any joke will kill and flood the engine. With the new magneto”used” it won’t go over 5k rpm but it’s not throwing the 12v low on the gauge anymore however I would feel better to replace the magnet and coil with brand new parts if I can source them right

 

[Lothsahn]

Try unplugging the red wire on the inverter (also known as a rectifier). If that prevents the 4-5k sputter, you know the problem is a bad inverter or bad coil. If unplugging the red wire doesn't change the symptoms, then you have a problem elsewhere.

Disconnecting the red wire completely disconnects the coil & rectifier from the battery, so your battery will stop charging. You can run a ski on a battery for a long time--this is just a diagnostic step to find the problem, not a long-term solution.

Also, ALL the fuel lines need to be automotive lines if they carry fuel. However, some of the fuel lines are simply vent lines to the outside of the ski. Those can stay grey. So if you have any fuel-carrying lines that are still grey, replace them, otherwise, you're fine.

 

[97 gtx]

Thank you! I’ll try to give that a shot and let y’all know.
Yea the majority of the main lines are switched but the vent lines are still grey and it looked like the couple hoses going to the carbs are grey also with it sitting for 2 years the gas tank was the first to clean then new filters then the carb but never checked the fuel lines until the other day.

 

[mikidymac]

You don't need the change the vent lines, just all the fuel feed lines.

 

[etemplet]

I'd check the 4 nozzles inside the carb barrel to make sure they are spraying a powerful stream. That's generally they problem I found with mine. Just wouldn't get over the hump and get cleanly on the main jets. Follow the carb rebuild thread for instructions.

You don't have to rush and reinstall the oil pump. It won't blow up if you don't. You'll get a lot of old school 2-stroke guys that will tell you to ditch the oil pump. They have a point and their reasons. I happen to be one of the old school two stroke guys LOL but I find it more convenient to leave the oil pump installed. That said, when you replace the oil pump you'll need to prime the system. We'll be happy to help with that. Good Luck !!

 

[AKnarrowback]

Anytime I see "97 GTX 5000 rpm's" I post this TSB. It is one know problem that might explain what you are dealing with. However, what you are describing isn't the typical scenario where the TSB would apply.

To test my 97 gtx I took it for a run with the seat off and pulled the rave valves open by hand to see it it would get over the 5k hump.

With the low hours and how clean that machine looks it is worth taking the time to get it figured out. That gtx is a really nice handling, comfortable, machine.

 

[etemplet]

Anytime I see "97 GTX 5000 rpm's" I post this TSB. It is one know problem that might explain what you are dealing with. However, what you are describing isn't the typical scenario where the TSB would apply.

To test my 97 gtx I took it for a run with the seat off and pulled the rave valves open by hand to see it it would get over the 5k hump.

With the low hours and how clean that machine looks it is worth taking the time to get it figured out. That gtx is a really nice handling, comfortable, m

Yes thanks for posting thatTSB. It helped me fix my wife's ski and it is still faster than mine now. LOL

Is it this cold in Alaska yet?? I use these pictures on the Facebook Forum to pick on the Louisiana riders like, "Only sissies winterize their skis."

 

[AKnarrowback]

Yes thanks for posting thatTSB. It helped me fix my wife's ski and it is still faster than mine now. LOL

Is it this cold in Alaska yet?? I use these pictures on the Facebook Forum to pick on the Louisiana riders like, "Only sissies winterize their skis."

We are 20 at night, maybe 32 or 33 during the day. Had our first snow last weekend.

The guys I work with get a laugh because the first snow, for me, means I better get a couple of more rides in before winter "really" starts. This year is done though, one test run on a repair job had me out on the first snow day, everything is getting winterized and stored.

Got bigger problems going..... Got vaccinated Monday and woke up looking like this today....

 

[97 gtx]

Thanks for the advice you guys I greatly appreciate it! I live out in the middle of nowhere I finally found someone who will gladly work on the ski with me to teach me about the rotax motor and best of all he only charges by the case of Budweiser! My kind of mechanic lol! Anyways I’ve got 3 main projects going on now my motor build in my lifted Silverado the Pre runner build on my Tahoe and the jet ski so I’ve kinda let the ski hang out for a bit but I’m planning on ordering a new magneto and pick up coil as the stock one was bad off the used one we installed looked better but was used and don’t know if it actually was much better then the one we changed out. New pet cock on the way also and a mikuni rebuild kit as the kit that is on the carb looks like a off brand and I don’t trust it.
Just need the time to work on it as I travel for work it makes it hard sometimes to tackle on top of my weekly household tasks and side business to run it gets busy.
I did however want to show off my “new” 96 Yamaha yz125 I just picked up last week it’s been fully restored from the frame up super super clean that’s also took up any free chance I get to go ride it lol

 

[97 gtx]

Might also be picking up another ski this week I get home if the wife don’t kill me lol my buddy has a 93-94 gts 587? New motor but everything else on the ski needs work like the cables steering start button hood Hinge seat etc but for 50$ figured it would be worth it to restore once I get finished with the gtx let me know yalls thoughts if it would even be worth it financially the gtx I’m at around 1000$ with the work so far including buying the ski and duel trailer so I feel like I’m still in the good right now just need the parts and time to get it situated so I can go riding on the 787 again been a busy this summer with it I hope to make a come back next spring or get a wet suit and ride this winter if I get it situated before the spring

 

[AKnarrowback]

The bike looks awesome. Going to be single by the time summer comes back and will be looking at getting a two wheeler myself.

Keep us up to date on the DOO progress. The 587 is a durable motor, pretty much the original sea-doo motor with a couple variations depending on the year. The 587 is based off the Rotax snowmachine line 580 motor that came out in the 89 Mach 1, the first snowmobile to have rave valves. The basic, rotary valve, liquid twin Rotax goes wwaayyy back with many different CC variations and decades of refinement before it was shoved into a watercraft. The gts configuration, if I remember right, was the original 55hp rating. The same crank, case, cylinder "beefiness" in the watercraft is the same as sleds and on the snow the 580 was between 80ish to 95ish HP depending on the year and configuration. The key thing is that regardless of the configuration the 580 Rotax is one of the most durable motors made. I have a 94 summit 580 in the yard that still runs perfect, I squeeked 100mph out of it last year. I have seen them modded upwards of 120hp, well past double what the gts is putting out.

 

[etemplet]

The bike looks awesome. Going to be single by the time summer comes back and will be looking at getting a two wheeler myself.

Keep us up to date on the DOO progress. The 587 is a durable motor, pretty much the original sea-doo motor with a couple variations depending on the year. The 587 is based off the Rotax snowmachine line 580 motor that came out in the 89 Mach 1, the first snowmobile to have rave valves. The basic, rotary valve, liquid twin Rotax goes wwaayyy back with many different CC variations and decades of refinement before it was shoved into a watercraft. The gts configuration, if I remember right, was the original 55hp rating. The same crank, case, cylinder "beefiness" in the watercraft is the same as sleds and on the snow the 580 was between 80ish to 95ish HP depending on the year and configuration. The key thing is that regardless of the configuration the 580 Rotax is one of the most durable motors made. I have a 94 summit 580 in the yard that still runs perfect, I squeeked 100mph out of it last year. I have seen them modded upwards of 120hp, well past double what the gts is putting out.

Wow.... no wonder these engines are dang hear bullet proof!! I had a 1996 SPI (587). My first ski I bought used a few years ago. It was pretty fast and I didn't learn to later that it had the Factory Pipe, with all the trimmings on it. I would run 47mph easy on the GPS. Fun Fun ski !!! Actually, that's all I needed but the road to excess as usuall.... LOL

 

[AKnarrowback]

I don't even know all the variations. The twin cylinder liquid rotary valve has been made in 340, 440, 467, 500, 521, 580, 617 and 670 as far as I know. The 340 and 440 were limited to production race sleds and not really sold on any floor models, the 467 was in the mx name through various chassis generations, the 521 was the formula plus starting in 85 up to 90. The 617 was short lived only showing up in the 91 and 92 Mach 1's (like the seadoo 657x) when the plus inherited a detuned version of the 580, the 670 came along in 93 and stayed on until the ZX chassis came out. The 500 came in around 96 and stuck around for a couple of years. The big drawback was the motor has the intakes mounted on the case to accommodate the rotary valve, when the snowmobile industry went to the "centralized mass" as the new basis of chassis design the rotary valve motor could not be dropped down and moved back due to the carb location so the rotary valve motor died out out production.sleds starting in 2003.