Hi guys, don't know if someone can help me but I hope so. I have a 1999 SPX that I got from someone where it had been standing for years. I have tried to get it going again but its giving me issues. I changed all the fuel lines from the grey lines, put a new battery in it and got the carbs and starter motor rebuilt at a dealer. They say they tested it afterwards and it was working fine before they gave it back to me. When i used it, it worked for about 5 minutes before it started jerking or missing. If you hold throttle fully open it jerks and splutters or if you hold throttle constantly at half its not smooth and jerks. After it starts this missing or jerking then once you switch it off then it doesn't want to start again and you have to swing for a while before it starts and then it won't idle unless you hold accelerator open slightly. I took it back to the dealer and they stripped the carbs in front of me, they found one creased check/pump valve and said that was the issue. They changed that, I took it to test, exact same thing, worked for 5 minutes then started with the missing/jerking etc. Phoned the dealer and they said it might be the plugs, i changed the plugs, didn't fix it. Phoned them back and now they say its probably the ignition coil that's faulty and needs to be replaced. I have tested the coil with a multimeter and the readings were correct as per the manual. I told the dealer this and they said you can't accurately test the coil with a multimeter as spark can break down when under load. I took it to an auto electrician who also tested it on a machine and they said its working fine. Dealer says that the machine the auto electrician uses doesn't simulate under load conditions and that the coil could still be faulty. I feel like i'm constantly spending money on things they think it might be and its not solving anything so thought maybe someone on the forum might know what the problem could be. Could it be the ignition coil still? Would the pop off pressure on the carbs cause this issue as I never saw the dealer test the pop off pressures? What else could it be?
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The coils very, very rarely fail so I would be suspicious of that.
What is the compression, I would check that first.
I would not trust this shop to do the carbs as they did not do the proper pop-off or pressure testing if they didn't know the diaphragm was bad. I would also be suspicious if they used all new Genuine Mikuni parts. I would want to see what kits they used for the rebuild.
To me it sounds like it is flooding and that is usually caused by the crappy aftermarket diaphragms.
What is the compression, I would check that first.
I would not trust this shop to do the carbs as they did not do the proper pop-off or pressure testing if they didn't know the diaphragm was bad. I would also be suspicious if they used all new Genuine Mikuni parts. I would want to see what kits they used for the rebuild.
To me it sounds like it is flooding and that is usually caused by the crappy aftermarket diaphragms.
JeremyD615
Well-Known Member
It definitely sounds like a fuel problem, and the dealer should know this. As much as I’m sure you’d like to take it back to the dealer for them to fix their mistake, I think I’d either buy the OEM carb kits and do it myself, or send the carbs off to a reputable shop to have them gone through... Unfortunately it sounds like they’re causing more issues than they are fixing at the place you were taking it to.
I also thought fuel starvation because its almost as though it runs fine in the beginning while the carb is full but using more fuel than the carb is getting in but then once it starts this jerking/bogging thing it wont stop even if you give it time for the carb to fill with fuel. Once its started the jerking/bogging thing, you can park the jet ski off for 15 minutes, and get on and try it again and the jerking/bogging is immediately still there.
JeremyD615
Well-Known Member
The rectifier is in the grey electrical box with the MPEM. It has a metal backing plate and has the three yellow wires and one red one run to it.
dan87951
Active Member
Sorry to hear about your problems! I wouldn't trust this dealer anymore, it looks like they are just throwing parts at it instead of trying to find the root cause. Unfortunately if you want to own of these older machines you really have to be able to work on it yourself or you could spend a small fortune teaching someone else (your dealer). Thankfully we have forums like this with members who have a lot of experience with these older skis. Have you tested the rectifier yet? I did a youtube video on how to test it if you're interested. You can check it out by clicking the link in my signature. If the rectifier is good then I would move on the carbs. Dealers don't see a lot of these older jet skis much anymore and don't have the experience to properly diagnose them.
If it were me, buy yourself a nice pop off gauge, a set of carb rebuild kits (including needle and seat), and completely go through the carbs again -- mikidymac has a nice DIY carb rebuild link in his signature.
. It really is much easier than you think. Before removing all the fuel lines make sure you label them and take tons of pictures so reassembly will go smoothly. If you have any questions we're here to help!
If it were me, buy yourself a nice pop off gauge, a set of carb rebuild kits (including needle and seat), and completely go through the carbs again -- mikidymac has a nice DIY carb rebuild link in his signature.
. It really is much easier than you think. Before removing all the fuel lines make sure you label them and take tons of pictures so reassembly will go smoothly. If you have any questions we're here to help!
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From reading various posts on this forum, I tried the following at the dam yesterday:
- Cut back plug leads and installed new plug caps in case there was corrosion and not continuous spark
- Cleaned up all the connections in the back electrical box and cleaned up earth/ground connection
- tried opening petrol cap while running
- tried riding with seat off (saw a post about exhaust leak and exhaust fumes choking engine)
- tried connecting a separate fuel tank direct to carb bypassing the pickup, fuel switch and filter
Nothing worked. Actually seems like the ski is worse now. Before it would run fine for 10mins and then start jerking. Yesterday it started the jerking problem straight away. If you hold throttle open, it will accelerate for a few seconds then stop accelerating for a second then accelerate again then stop accelerating and if you keep throttle open the whole time the period of no acceleration gets longer and longer where eventually the no acceleration period is longer than the acceleration period and engine noise doesn't sound good.
Ski runs perfect on the trailer with or without hose but as soon as you put it in the water it starts this problem.
- Cut back plug leads and installed new plug caps in case there was corrosion and not continuous spark
- Cleaned up all the connections in the back electrical box and cleaned up earth/ground connection
- tried opening petrol cap while running
- tried riding with seat off (saw a post about exhaust leak and exhaust fumes choking engine)
- tried connecting a separate fuel tank direct to carb bypassing the pickup, fuel switch and filter
Nothing worked. Actually seems like the ski is worse now. Before it would run fine for 10mins and then start jerking. Yesterday it started the jerking problem straight away. If you hold throttle open, it will accelerate for a few seconds then stop accelerating for a second then accelerate again then stop accelerating and if you keep throttle open the whole time the period of no acceleration gets longer and longer where eventually the no acceleration period is longer than the acceleration period and engine noise doesn't sound good.
Ski runs perfect on the trailer with or without hose but as soon as you put it in the water it starts this problem.
JeremyD615
Well-Known Member
Did you ever get back into the carbs? Do you know if the diaphragm has a red nipple or a silver nipple on it? I’m still suspicious that the dealer either didn’t get the carbs completely clean, or used aftermarket parts in them...
I didn’t go back into the carbs to check. Someone told me that if it was fuel then the problem would happen all time whether on trailer or in water and that the problem must be electrical as the problem was only happening once the ski had warmed up and when it was under load in the water and suggested ignition coil. I didn’t replace ignition coil just thought I’d try clean up the electrical connections and cut back leads and got new plug caps to see if that would help as that was a cheap solution. Also read a lot of forums with ski’s that had similar problems and tried some of those suggestions. Could an issue with the carbs cause it to run fine on the trailer and then give issues in the water?
JeremyD615
Well-Known Member
Yes, whoever told you that fuel issues would show up running on the trailer is giving you bad advice... How the ski runs on the trailer will tell you absolutely nothing about the ski other than it starts. When running out of the water, the motor has no load on it at all, so you can bounce it off the limiter without ever opening the throttle blades beyond 10-20%. If you have corrosion clogging your transition ports or a bad diaphragm, it will never show up outside of the water, since the engine will rev to the moon with very little fuel...
I’d suspect the carbs before I did the ignition coil. It’s possible that it’s the issue, but it’s very rare for one to go bad like that...
I’d suspect the carbs before I did the ignition coil. It’s possible that it’s the issue, but it’s very rare for one to go bad like that...
Ok I see, Will try pull them off and have a look. Can low engine compression also cause this issue? I haven't checked engine compression, just thinking maybe I should check that before pulling the carb apart. If it can't be that I will start with the carbs.
I don't have many tools, what would I need to check pop-off pressure? What would be the symptoms of the pop-off pressure being lower than it should be? Just wandering if it couldn't be that?
I don't have many tools, what would I need to check pop-off pressure? What would be the symptoms of the pop-off pressure being lower than it should be? Just wandering if it couldn't be that?
Cheflen
Active Member
This really sounds like your voltage regulator. Had this happen when I bought my 96 xp. It would feel almost like it was hitting rev limiter at around 3k rpm. I rebuilt my carbs and replaced the fuel lines to have the same issue. Once I replaced the voltage regulator/rectifier this went away. What you are describing sounds exactly like the voltage regulator issue and is very common on the 787’s. This is very easy to test.
Put the multimeter on your battery and start the ski. You will see that it’s overcharging and causing the engine to sputter.
Or you can just throw a voltage regulator at it since it is cheap and very easy to replace.
I will strongly advise you to replace this as it is cheap and easy and you will be chasing your tail without it. This really sounds like your voltage regulator
Put the multimeter on your battery and start the ski. You will see that it’s overcharging and causing the engine to sputter.
Or you can just throw a voltage regulator at it since it is cheap and very easy to replace.
I will strongly advise you to replace this as it is cheap and easy and you will be chasing your tail without it. This really sounds like your voltage regulator
JeremyD615
Well-Known Member
If the pop off pressure were low, you’d be rich, and I if it were low enough to cause your issues, I’d think you would be fouling spark plugs left and right... Low compression usually first manifests itself as a hard start while in the water, so I don’t think thats your problem, although it’s always good to check.
Once again, the regulator/rectifier is a definite possibility as well... You can test this by opening the grey electrical box and disconnecting the red wire that’s coming into the rectifier with the three yellow stator wires. Of course you won’t be charging the battery with it disconnected, so don’t run it too long like that...
Once again, the regulator/rectifier is a definite possibility as well... You can test this by opening the grey electrical box and disconnecting the red wire that’s coming into the rectifier with the three yellow stator wires. Of course you won’t be charging the battery with it disconnected, so don’t run it too long like that...
Cheflen
Active Member
It’s hard to know if it was overcharging if it “revved pretty good” while testing. Since this happens a few minutes into riding it’s hard to tell. I hate to suggest throwing parts at it but I would replace it just for safe measures.
BUT if you want to do a true test on it, unplug the red wire from the voltage regulator and ride it. If your problem goes away then you know it’s the regulator. Just remember your battery will not be charging so don’t go far from the dock.
The voltage regulator is in your front e-box and has 3 yellow wires and a red wire coming from it
Ckrawiec
Well-Known Member
You need a good compression guage....Harbor Freight compression test guages are JUNK btw.
Take spark plugs out, thread guage in, start the ski...the pistons will pump and the guage should take a measurement. Do both sides, write down what you get...both cylinders should be roughly equal (150 psi is close to ideal - I believe...or something in that neighborhood..) test a couple times
The advise you have received so far is right on:
1) Rectifier/Regulator could be a culprit (relatively cheap and easy to test and/or replace)
2) CARBS - my money is on the carbs......the root of MOST evils in these skis....they are persnickity.....they need to be dialed in just right.....using only GENUINE MIKUNI parts (everything else is a fools folly).....MANY have chased their tail with non-mikuni parts and eventually capitulate into MIKUNI parts (and saved their sanity) - BEEN there ->done that.
3) BTW: These skis need a good strong battery to get things going, so ALWAYS START with a known good, strong, load tested battery.
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