pistons holding sludge?

[onesojourner]

I have been having some serious issues http://www.x-h2o.com/threads/54523

any ways I noticed that the top of my pistons looked pretty sludgy on top. here are some pics. is this normal?

 

[Pro-pulsion]

It looks like semi-burnt oil. What type of oil do you use? I read your posting in the link and I think you might have coil issues. Sometimes when a coil is getting weak it will not have the ability to jump the spark across the gap after the plug has some carbon there to partially insulate it. Replacing the plugs reduces the resistance that the coil has to deal with making it easier to jump the spark. There are two other areas that you can look into first though. Check the resistance of your spark plug caps. There are a lot of NGK plug caps out there with built in resistors and they are junk! When those resistors start to go all kinds of weird things will happen and eventually there will be no more spark. If you don't have these type, the next possibility is that the plug leads need to be trimmed because there is only a few strands making contact with the threaded post inside the plug cap. Over time the wires will break down and fall out of the cap from vibration or being over-cranked by whom ever screwed the caps on. They twist those caps one too many times and it breaks the wires off. As for the pistons, if there isn't enough spark there to fully ignite the fuel charge the heaviest remains will just dry up on the piston leaving what you have as the result. Can you post pics of the first couple of sets of plugs? I'd like to see how they're burning.

 

[onesojourner]

I am running penzoil right now.

 

[Pro-pulsion]

Well, I don't have any experience with Penziol, my brand is Maxima Marine Pro, I love that stuff. It's a bit more expensive but it doesn't carbon up and the ski seems to like it a lot more. Oh yeah, how about plug pics? I also forgot to mention that it's not uncommon for a coil to heat up and break down when it gets old and starts to fail. After they cool they'll start to work properly again just encase the issue isn't in the caps or leads.

 

[onesojourner]

I have ran 2 coils and it didnt solve the issue so I dont think it was that. plug pics coming up.

 

[Pro-pulsion]

Well, I'm off for the night dude, I'll check back in the morning.

 

[onesojourner]

plug pics.

 

[Pro-pulsion]

Hmm...it's def. no too much fuel. It looks like either the timing is retarded and the oil isn't getting burnt up fully, or there may be an issue with the injector if you still use it, or the oil its self. Check your timing first to make sure everything is good and if so, move up to a higher quality oil. Oh yeah, what grade of fuel do you run? If you're on the regular stuff and you're pushing 160psi or more you should move up to 92 minimum. I've often experienced regular gas as being a problem even in stock compressions. It flashes way before it gets to BTDC and takes forever to start the engine. But when the engine is cooled down it will start pretty easily because there's not enough heat there to flash it before it reaches its mark.

 

[onesojourner]

this is an sj so its premix. I am at 150 psi (at least I was last season) and I run 89 in it.

 

[Pro-pulsion]

Yeah I wasn't sure if SJ used injection or not. 89 is ok for around 150 but even then it's getting a little bit much for 89 to work well with. I'd check into the timing components first and make sure everything is good there. Then the next least expensive thing you can do is try a better brand of oil. That stuff just might not burn well enough for that range of compression. Just my .02 but to me, a company can't be good at everything. I use Castrol 2-stroke in my chainsaw but would never run it in my ski...their focus is automotive and that's where the priority is set. Brands like Spectro, Maxima, Amzoil, they focus on the small engines where the variables are a lot different. And at least you would determine if it's oil related or not :biggrin:

 

[Pro-pulsion]

Just another quick thought, what year is your ski and have you ever changed the reeds in it?

Edit* I just seen the year of your ski in your signature lol...but the reeds question still stands :biggrin:

 

[onesojourner]

2000. This is my 3rd season on it and I have never touched the reeds.

 

[Pro-pulsion]

If they haven't been done before you owned it then it's a good idea to look into it. Eventually they get tired and will hang open not sealing to the cages. Just that alone will give back performance. I just checked the online fiche and yours has 4 sets per cylinder so it may be a bit of a cost to replace them but well worth it. Let me know how you made out with your timing marks and hopefully it's just a simple mark misalignment.

 

[Pro-pulsion]

Do you have a service manual for it? I might have one. I have to head out for a few hours right now but get back to me and I'll do what I can to help out.

 

[onesojourner]

yep I have a manual.