Help, sj suddenly shut down

[Mike Grafas]

97 rn with raider motor
Ada head, bpipe, lightened flywheel, oem coil, msd enhancer set to lowest rpm limit, dual cooling
Yesterday I was riding chasing boat wakes and as I was full throttle catching up to this boat the ski shut down. I tried cranking it and it didn't sound right but that could be my imagination, I had to pump the primer and it fired right up.
Took it slow blipping throttle and everything felt fine, went back to full throttle and all was good, ride for another hour and it never missed a beat.
First thing im going to check is the start stop switch but if anyone can lead me to what else could cause this is appreciate it

Also before anyone thinks it's a cold seizure or a fuel selector(replaced a few months ago) keep in mind I ride at least 4 days a week and never had an issue like this before

But like I said it ran great afterwards like normal
Thanks guys

 

[TheBuzzard]

sounds like it lean seized at wide open throttle. especially since you pumped the primer and it started back up. turn the high speed screws out a turn or more. that'll learn you to hold it wide open for extended periods. recipe for disaster, hold it WFO. plugging fuel filters can cause it to die at high RPM too.

 

[Mike Grafas]

sounds like it lean seized at wide open throttle. especially since you pumped the primer and it started back up. turn the high speed screws out a turn or more. that'll learn you to hold it wide open for extended periods. recipe for disaster, hold it WFO. plugging fuel filters can cause it to die at high RPM too.

Yeah but like I said earlier, riding 4 days a week and almost always going wot I've never had this
So why would it leaning seize all of a sudden and then run great
Is it possible to have a slight lean seize and not cause any damage? Which is why it ran mint afterwards?

 

[Mike Grafas]

And also priming it could have been a coincidence, it's possible it would have started if I tried cranking it again, I just thought it sounded like it wasn't cranking right

 

[Mike Grafas]

Now that I think about it, I have my high speeds set on the rich side on purpose
So I can't imagine it would be a lean seizure

 

[augustaf]

Suggest you check the cranking pressure (compression), that should tell if you had a (partial) seizure.

 

[Mike Grafas]

Suggest you check the cranking pressure (compression), that should tell if you had a (partial) seizure.

Checked battery connections, start stop switch, all connectors, did compression check (170 psi cold in each cylinder) and borescoped both cylinders and they look clean with no scoring on pistons or walls

I guess I'll have to see if it does it again

 

[Mike Grafas]

So the same thing happened today after a few wot runs
The first few runs we're fine but did about a 1/2 mile run and shut down

This time I tried starting right away and it started but then stalled
Then started again but acted as if it was loaded up then stalled
Third time it started and ran good(wasn't pinning it, just blipping throttle)
After blipping for a few seconds it ran just like normal
When I got to my shop I borescoped and compression checked and everything checked out
Any ideas?

 

[Mike W]

I would definitely stop anymore WOT runs until you figure it out. Sounds like maybe a fuel flow issue. I would start with inspecting your carbs just to rule them out then go from there.

 

[Citizen]

Had a similar issue, check your fuel filter and internal filters in the carbs. Ski would run great except at high throttle where it would shut down on me, wasnt getting enough fuel.

 

[Mike Grafas]

So I randomly realized today that I glassed in my front intake holes on my hood.

I never opened the rear holes bigger because it ran fine with low end

Is it more than likely that I'm choking the motor out and that the rear vents cannot pull in as much air as the motor is pulling, causing it to stall out

It would explain the instant restarting and no loss of power or compression

Would this be a possibility?

 

[Citizen]

I doubt it, i turfed over those holes on two of my superjets with no ill effects.

 

[Mike Grafas]

If this is the second time this has happened and I do a lot of full throttle runs, except most of the time I let off for a second till I'm about to come off plane then hit it again, wouldnt I see some type of sign of lean seizure

I would imagine if I'm running lean on top end then anytime I went wot I would start to see signs

Or is it possible it's not enough for me to see?

Keep in mind I ride about 4 days a week about an hour each ride

Mostly always I go full throttle once or twice during the ride

 

[FX1 696]

I second the fuel filter suggestion, my FX1 would idle and run fine at slower speeds. I would go wide open and she would die from not getting enough fuel. They're really cheap at the hardware store, just grab a lawn mower one.

 

[Mike Grafas]

I second the fuel filter suggestion, my FX1 would idle and run fine at slower speeds. I would go wide open and she would die from not getting enough fuel. They're really cheap at the hardware store, just grab a lawn mower one.

Yeah that's what I have now, the little inline mower ones except a really good one.
And I'd get it if I went full throttle and it would stall, but how am I able to go wot for at least a half a mile before she quits
If I was running lean on top end wouldn't I have blown the motor a long time ago
Someone correct me if I'm wrong, if maybe it's "slightly" seizing if that's a thing

 

[Mike Grafas]

Well I feel like an idiot, I know I said I kept the high-speed screws on the rich side. But after looking further into it I must have leaned them out a little bit when I was trying to tune the ski in the winter time. I remember I couldn't get the low-end right so I thought let me lean out the top end so I can rule that out. Turns out my high speed screws were only about one and a quarter turns out, brought them both the two turns out and and feel pretty safe now. Definitely feels like I lost my top end, obviously, but I'll have to put a GPS on it, I was at 49.5 miles per hour before.
Live and learn

 

[Harbor]

Well I feel like an idiot, I know I said I kept the high-speed screws on the rich side. But after looking further into it I must have leaned them out a little bit when I was trying to tune the ski in the winter time. I remember I couldn't get the low-end right so I thought let me lean out the top end so I can rule that out. Turns out my high speed screws were only about one and a quarter turns out, brought them both the two turns out and and feel pretty safe now. Definitely feels like I lost my top end, obviously, but I'll have to put a GPS on it, I was at 49.5 miles per hour before.
Live and learn

shonet happens, done it too...
You might want to remove your top end for an inspection instead of a full speed run. If you've got piston metal transfer to your cylinder you could hang a ring and cause more damage. With a light seize, piston metal usually malls up and across the ring lands some and interferes with rings operation. With a light seize metal can be removed from your cylinder wall with muratic acid, light hone and 2 new pistons and rings...

I guess you could also first do a compression test and compare numbers to previous numbers, pull the head and visually inspect your cylinder walls, also with your fingers push your pistons side to side pto to flywheel direction and intake to exhaust direction and check that the rings slid in the ring lands in all directions still. This could give you some indication if you need to pull the cylinder...

I found on my engine after winter by random chance that one Pistons rings had stuck via carbon or ?... With the push method I mentioned..
No seizing but I could have hung a ring if not discovered. I lubed rings from the top, only head was off and worked them free. Now if she sits over winter I check piston ring lands thru the spark plug hole. With an (all) or pic I see if I can push piston in all directions and check piston movement across the rings....

 

[Mike Grafas]

shonet happens, done it too...
You might want to remove your top end for an inspection instead of a full speed run. If you've got piston metal transfer to your cylinder you could hang a ring and cause more damage. With a light seize, piston metal usually malls up and across the ring lands some and interferes with rings operation. With a light seize metal can be removed from your cylinder wall with muratic acid, light hone and 2 new pistons and rings...

I guess you could also first do a compression test and compare numbers to previous numbers, pull the head and visually inspect your cylinder walls, also with your fingers push your pistons side to side pto to flywheel direction and intake to exhaust direction and check that the rings slid in the ring lands in all directions still. This could give you some indication if you need to pull the cylinder...

I found on my engine after winter by random chance that one Pistons rings had stuck via carbon or ?... With the push method I mentioned..
No seizing but I could have hung a ring if not discovered. I lubed rings from the top, only head was off and worked them free. Now if she sits over winter I check piston ring lands thru the spark plug hole. With an (all) or pic I see if I can push piston in all directions and check piston movement across the rings....

Alright I'll do that, I've got some down time anyway, broke my pump shoe yesterday
But compression only fell off about 3-5 psi
But she definitely ran good yesterday