This melt down just might have me stumped..

[speedysprocket]

Running the cylinders too cool from too much cool or cold water causes seizures too... Piston still gets hot and expands, but the cylinders don't expand as much as you expected them to, and you get a "cold seizure"...

 

[SXIPro]

Running the cylinders too cool from too much cool or cold water causes seizures too... Piston still gets hot and expands, but the cylinders don't expand as much as you expected them to, and you get a "cold seizure"...

Good point.

 

[Roseand]

Running the cylinders too cool from too much cool or cold water causes seizures too... Piston still gets hot and expands, but the cylinders don't expand as much as you expected them to, and you get a "cold seizure"...

It's possible, but very rare from what I understand. I can see it happening with very cold water temperatures and starting it right up and pounding it right away, but who does that? As long as you get it warmed up before pinning it you should be fine, and if you are running in very cold water you should properly restrict it to avoid that from happening to begin with...

 

[SXIPro]

It's possible, but very rare from what I understand. I can see it happening with very cold water temperatures and starting it right up and pounding it right away, but who does that? As long as you get it warmed up before pinning it you should be fine, and if you are running in very cold water you should properly restrict it to avoid that from happening to begin with...

Lots of guys do that, and it's scary especially if they happen to have Wisecos.....ouchie. Not hating on Wisecos, as that is what I run. I would say 80 percent of the guys on my lake go from green button to WOT in about 2 seconds. I just shake my head.

 

[Roseand]

Lots of guys do that, and it's scary especially if they happen to have Wisecos.....ouchie. Not hating on Wisecos, as that is what I run. I would say 80 percent of the guys on my lake go from green button to WOT in about 2 seconds. I just shake my head.

Totally! With forged pistons that's like playing with fire... Not smart. I usually make sure my pissers are up to normal operating temperature before going over half throttle, and I wait at least 30 seconds to a minute before I even give it any gas really. Better safe than sorry!

 

[SXIPro]

Totally! With forged pistons that's like playing with fire... Not smart. I usually make sure my pissers are up to normal operating temperature before going over half throttle, and I wait at least 30 seconds to a minute before I even give it any gas really. Better safe than sorry!

Yep. My neighbors probably think I am just trying to annoy them while I stand in the water and hold my ski while it idles...... blub, blub, blub, blub. But they're the ones with two toasted skis under a tarp while I'm out playing on the lake.

 

[Dartman]

just hone it to .0055 piston clearance with prox cast pistons
reseal, wash out or what you want to do with lowerend
put in the 2.0 n&s
go up 1 or 2 sizes on the main jet
if you can, buy a msd enhancer it takes a little more risk out by gaining a couple of degrees of retard with the timing

 

[Sparkplug]

Dual cooling on a engine that doesn't need it can easily cold seize. Most cold seizures go unnoticed. Shrugged off as a air bubble in the fuel line, or a intermittent electrical issue. Your friends riding your ski would almost definitely not be able yo tell a cold lean seizure, unless they are familiar with engines. You have to realize at wot things are moving extremely fast. Temperatures are changing extremely fast. A difference of 10 degrees in the water at wot with dual cooling could cool the cylinder enough so quickly that it seizes.

An air leak would fail a pressure test. Almost definitely. 99 percent. Unless it was such a small leak it needed the engine at operating temperature.

Anyways. I hope you get it fixed and back on the water as soon as possible. More knowledge is never a bad thing, and there is no such thing as a dumb question.

 

[txsuperjetfreak96]

So when should we justify going dual cooling 900cc 1200cc etc etc


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[kevbo]

It is the hotter combustion temps caused by a cold intake tract that stick pistons. Cooling water runs through a light weight aluminum exhaust manifold that heats up in a few seconds. What do you think makes a bigger difference, combustion temps 200 higher or water 40 cooler?

 

[Sparkplug]

Your pistons at wot extended are close to seizing. They are tight in their bore. Couple that with DUAL cooling. And a cold patch on top of the lake, and your pistons can easily be a press fit for a millisecond. Also known as a cold seizure.

Not sure what you are saying kevbo? That most times it's the intake air that causes a cold seizure? On a 2cycle? I don't agree. If this was the case wouldn't you see most of the damage focused on the intake side of the piston? Again. Always looking for more information.

 

[Jakobi86]

I feel that the only way to cold seize these motors with this open loop cooling system is to do it initially after start up and pin it to wot. Once the manifold has a chance to warm up, so will the water that runs through it, and the water that hits the cylinders will already be pre warmed by the manifold. Now if these motors had a thermostat, that's when you'd see cold siezes. IMO, the hardest thing on these motors is from start up to when the pisser is warm. After that, I think, you can do as much wot, with as much cooling as you want, through any type of water you want, all things considered.

Also, if intake air caused cold siezes, then sleds would blow up all the time. Think about it, they draw sub zero air into a hot combustion chamber and do just fine. They cold sieze when it's not properly warmed up and the inrush of cold, unheated coolant hits the hot cylinders


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[kevbo]

If the mixture is tuned for best power at 90-100F, any temp lower raises combustion temps. Cooler water plays a part although much smaller. I run more piston clearance these days along with the carb set a few rpm rich of peak power. This allows for a lot of abuse without sticking a piston.

 

[Roseand]

Ski is back together and rejetted/lowered popoff pressure too. Will post results!

 

[Roseand]

Went to a 2.0 n/s and it gave me 20 psi popoff. I think I might raise it a bit when I pull my carb. It occasionaly loads up and needs to clear out to be crisp.
I went up a size on the main and the pilot, and hopefully I can stay at that pilot.

I'm at 152.5 main and 127.5 pilot. At 3 turns out on the high speed there is zero crispness and you can tell it's rich. 2 turns still feels rich and at 1.5-1.75 turns out it feels fairly good. Haven't tried any further in yet since I didn't have a tach. It definitely doesn't hit like it did before it blew up lol.


I did a plug check after running 2/3 to full throttle for a couple seconds with my high speed turned out, and the plugs looked almost the same as with 3 turns out.
I ran at high speed and WOT at 3 turns out for a couple second bursts and then a solid 5+ seconds before shutting it off and swimming it in to check plugs.

Rear plug has the new piston and rings.

Why would the PTO side be so much darker? Because it's not broken in yet and plug readings aren't accurate? There is no air leak. Pressure checked it yesterday again and it was fine.
Thoughts? Need advice, Im lost

 

[BruceSki]

Have you tried putting the nose of the ski against the dock and tuning the high speed screw? I did this the other day and it's way easier than tuning WOT runs then yanking the hood and turning screws.

You can get the low speed pretty close like that too. It's similar to a test tank.

 

[Roseand]

Have you tried putting the nose of the ski against the dock and tuning the high speed screw? I did this the other day and it's way easier than tuning WOT runs then yanking the hood and turning screws.

You can get the low speed pretty close like that too. It's similar to a test tank.

Yeah I did that earlier with my trailer but I wanted to test it when riding it too.. For some reason I feel like I feel the differences better kinda. Lol Idk.. It's not the high speed tuning I'm work about, I'm gonna get a tach too. It's the wierd plug readings..

 

[Roseand]

My reeds looked fine using a mirror and a flashlight.. But maybe they aren't perfect. They're carbon techs with a max of 10 hours on them.

 

[BruceSki]

Can't help ya there. I'm anti single carb. Duallies for the win.

 

[Roseand]

My ski runs like it should with the high speed jet and high speed screw so I have a hard time believing it's a bad reed or an air leak. It's not a tuning nightmare. It responds to screw and jetting changes exactly like it should.