Pop off psi, what should I be aiming for?

[Harbor]

I've seen a lot of driveability issue caused by incorrect spark plug application, ie fancy materials/designs a paticular ignition system was not designed for...

In your case with a drivability concern I'd rather see you use the standard NGK BR8ES resistor spark plug if using Ada or aftermarket head requiring the long reach plug while you sort the issue out.

Once you've got her fixed, if you'd like try the iridium and see how it works do so then not now...

Personally I would not use them in this application. Hope this helps

 

[superjetincairns]

Ok thanks.
It's the first I've ever heard of issues with iridium plugs. I've always had better starting, idling and never ever fouled one so I thought I'd chuck them in since was putting new plugs in anyway. I have the br8eix fitted, same heat range as standard and still a resistor plug but longer than stock to fit the ada head. I guess I can try swapping back to a cheap stock plug if I can't get to the bottom of this issue soon, I'm gonna try all of the free options first though before I go buying more sparkplugs

 

[Fro Diesel]

First you heard that iridiums are not good? Wow, have yet to see a manufacturer use iridiums in an oem application. Some people believe that a salesman is giving them technical knowledge, but they are feeding you bs. A copper sparkplug is by far the best in most applications. Sounds like the same logic used to put a spoiler on your car....to make it go faster...fwd baby.

If you want a specific jet ski sparkplug. Get the right NGK plug, with a solid top. Not a screw on top, they can become disconnected due to the vibrations.

 

[Harbor]

No issues with uriduim......

However it's just like you mentioned @pro diesel, improper spark plug for his application.

 

[superjetincairns]

ok so ive replaced the iridium plugs with br8es plugs to see if that solves my issue. (im very doubtfull about this one but im getting desperate.) hopefully I can get some time on the boat ramp tomorrow if its not too busy and get this lemon to rev!
wish me luck!

 

[Dartman]

plugs is not your problem

 

[superjetincairns]

I don't doubt for a second that the plugs have nothing to do with this but swapping them is cheap and easy so it's crossed off the list. I'm pretty sure I'll be back to the iridiums a after the next test, only time will tell. It doesn't sound like ignition breaking down at all. No sputtering, misfiring or anything like that, it just goes puh! when I crack it open to above 1/2 throttle and dies. If it was one of my dirt bikes I'd be draining the water out of the float bowl or cleaning the main jet out because the symptoms im getting are exactly like that and I've had that plenty of times during 30 years of racing/riding motorcycles. I've swapped jets, cleaned carbs, swapped diaphragms, spark plugs and adjusted mixture screws, checked compression, all that's really left is to lower the pop off pressure and after that it can only really be a horrible bottom end air leak I suppose but I'd assume that would affect the running down low to some extent and the crank and seals have less than an hour on them. A crook msd ignition maybe? Reeds and blocks were replaced with a used set from jm and they looked immaculate like they just came out of a yamaha box brand new so it's not them. (Thanks chris)
I just hope there's not too many boaties at the boat ramp in the morning because they'll be whingeing about that 'jerk revving his jet ski on the trailer and not even riding it anywhere' but there's too many crocodiles here to risk going for a ride and breaking down im afraid.

 

[superjetincairns]

Could the over temp sensor being removed cause this? I read a thread on here that said to just tape the wires up in the e-box separated from each other so that's what I've done. Is that correct or should they be shorted together or does the sensor have to stay in the circuit but not installed in the head, just stashed away somewhere? Talk about grasping at straws

 

[Harbor]

Good for you, took out those plugs... I have a set of 38's down stairs coming off an engine very similar to yours, only type 4 pipe not a Riva red. I think I'll pop one open and see what's jets and the pop off measures with a gauge. These carbs work perfect.

I re-read all your posts and you've mentioned a few variables with the wsm carb parts.. You've done a lot with pop off, jets, seats. Going up and down but boat still seemingly acts the same....

Kinda seems to be pointing elsewhere like ignition related, msd, stator, coil, over heat rev on etc., but hard to tell with wsm variables mentioned..

I'am gonna measure these then pop one open. I could send these to you if you'd like to try a known good set, on manifold with reads

 

[Vumad]

Do you have access to a stock ignition? My msd failed. my ski broke up some then Eventually wouldn't start. I thought it was the starter. Put in all new cables and etc still would turn over then stop: put in stock ignition and it runs perfect. I think the timing started getting out of wack as it failed. Has worked perfect since I put the stock ignition back in.

 

[Harbor]

Main jet 140
Pilot jet 77.5
Seat 2.0
= pop off 28/30 with wet seat
High speed screw 1.6 turns out
Low speed screw 1.5 turns out

@ Seal level.. I left adjusters a little fat for safety with new rider..,
Msd enhancer, stator at 0, type 4 with continues water injection, 190 psi, 96 Superjet with stock pump and SS prop, OE coil with wires cut back at plug caps, old limited boat

 

[Vumad]

Also don't use anything but mikuni carb parts. I bought a sbt kit and the ski was untunable. The am kits are terrible. I couldn't even get my carbs to test out with the sbt kit. I actually had to use the 10 year old oring to get the fuel pump to stop leaking because new sbt is more out of spec than old mikuni parts. Have had the same problem with popoff and such. poop, the wsm pilot jets don't even have a size stamped on them. They are cheap and terrible. Anything not genuine mikuni you should replace.

 

[superjetincairns]

I did have my doubts about the carb rebuild kit but installed it all before I found this forum and read all the horror stories, jets and diaphragms are genuine parts though. The fuel pump parts all look pretty good, discs are sitting nice and flat and I don't have any leaks so im hoping that part is working ok. Stator is a used oem part from jm and as usual with his stuff it looked practically brand new. New plug leads were installed into the coil as well. Could lead type/ material cause this? (Doubtful) I think I used stainless spiral wound carbon core silicone leads 8mm. msd rev limit is set to max also. I dissassembled/cleaned/inspected every electrical connector on the whole ski during the rebuild. If the lower popoff pressure doesn't make a difference today I may need to try and borrow another ignition module to eliminate the msd unit.

 

[superjetincairns]

Ill try to pay particular attention to weather the fault is more rpm related or throttle position related today.

 

[jetx]

My guess is electrical related...your jetting and pop off is in the right ballpark for your setup, if there is no other issues it will rev up normally even if your jetting and pop off are not perfect....id start with swapping msd with a stock Cdi and than the coil you swapped the leads on. Just my 2 cents.

 

[superjetincairns]

Lower popoff made no difference didn't get long to test at the ramp as the weather is still and perfect for reef fishing here today, boat trailers lined up for miles. It looks like I'm heading back into the e- box for a play, yay for me!

 

[Dartman]

the pink wire from the cdi needs to be left unplugged (overheat limiter)
just tape it up good

 

[Bar jumper]

Pull your fuel return line off in make sure youve got a good flow , the slave carb outlet has a tiny hole that acts as a restricter it can block and as fuel pressure rises with rpm can push your n/s open and flood . Also check your pop off again with the carb diaphragm and cover on , if the arm is bent it can make a huge difference

 

[superjetincairns]

I checked the flow restrictor in the slave carb, sprayed it with contact cleaner and blew it out with compressed air, it's a pretty small hole but I can see through it. Any idea how small it should be?

 

[JetManiac]

I checked the flow restrictor in the slave carb, sprayed it with contact cleaner and blew it out with compressed air, it's a pretty small hole but I can see through it. Any idea how small it should be?

If you can see light through it then it should be good.