Burndown determination??

I run premium in my sleds all the time for the last 20 years, and I've always tried to get gas whenever available so it had been rare in the past if a full tank of 10% had ever gone through it. Now it's getting harder and harder to find gas without E in it and I'm guessing half the places down here that sell premium without E still have the E in it ... I'm leaning towards fattening all of my sleds up and draining the tanks and carbs this year. Engines are too friggin' expensive.
 
personally i think the gas is a problem too, but there are ways to deal with it (jetting, trying to buy from places with high turnover, additives, and so on...) I just don't think we have to sling mud at each other over differing opinions, we all have them... among other things
 
The only problem I have with the bad fuel theory is why is it only one piston out of three that has a hole in it. Don't the other two get the same air/fuel mix? I think it's a plugged jet or a carb boot issue. I will agree there is an ALARMING amount of vipers going down this winter. For the last few winters on here there were very few engine problems and they were mostly because of pipes and porting issues.
 
my opinion on only one cylinder is that one got the gulp of saturated crapinal i dont know why though, in one lungers if they get bad fuel you no right away they bog or stop running, in outboards there stacked. and bad fuel usually takes out bottom cylinder(depends on fuel delivery routing),but in inlines like sleds the fuel pump has seperate lines for each carb, so if you get a drop of saturated fuel in pump, oil and fuel go one way saturated crapinal goes the other, plus the crapinal its self is thining the oil the hole time its mixed. sorry for spelling im a tech not a secretary lol
 
SRX M10 said:
The only problem I have with the bad fuel theory is why is it only one piston out of three that has a hole in it. Don't the other two get the same air/fuel mix? I think it's a plugged jet or a carb boot issue. I will agree there is an ALARMING amount of vipers going down this winter. For the last few winters on here there were very few engine problems and they were mostly because of pipes and porting issues.
Click to expand...

this fellow lost the mag cylinder, which is known to be the hottest running cylinder on a viper. the mag cylinder also has a tighter dome in stock form, than the pto side, or like srx heads. tighter domes = higher compression, which = higher temps. now if he gets some 87 octane in there, instead of 93 octane, or 84 octane instead of the 87 posted on the pump, it will cause higher running temps, due to the lower octane. higher octane burns cooler/slower by the way. now, if he has some jets that are getting just a little bit plugged, then the lean condition sets in and temps get even higher. with the hole that he has melted thru his piston, showed that his egt temps were scorching hot. vipers have a hot timing too, so lets say he's running on the midrange, where the vipers can be lean and then you combine that with poor octane higher burning temp fuel, and you will get this kind of burndown. you might need to bump your mains up to 157.5 from the stock 156.3, to help keep things cooler towards the top end of the range. maybe even change the nozzles out too? i think it may have been a couple of things that added together to cause this, but i'm going to say that i believe the bad gas had a big role in this burndown.
 
Wow. Seems to me that the ones screeming the loudest about ethonal blended fuel are also the ones that can't put a freekin' sentence together!

Now, I'm no English major (highschool drop-out actually), nor am I an office manager (secretary - for you knuckle draggers), but perhaps folks would take you guys a bit more seriously if a) you weren't so personal and b) didn't come across as a "no it all".

My guess is that I've got more 'under-hood time' both professionally and under the shade tree than both of you put together, but I wouldn't presume to know that for a fact nor would I pretend to know what went wrong with this Viper and can only guess based on the pics provided.

We know the PTO cylinder sees more heat than the other two.

Okay, here it is, JMHO... not enough wash for my taste but agree that it looks like deto to me. Which overheated the ring land, stuck the ring and the rest as they is history.
 
Why has no one asked what the conditions of this melt down were ??? low snow ?? sled warm ?? racing across a lake ?? trail riding ??? just after a fuel up?

Not enough information to make a GOOD diagnosis....just keyboard guesses.
 
wow is right on this . I've never seen a burned up piston like that. I guess i need to get out more..... It defeniately looks like it burnt from the bottem up though , almost like it had a blockage in the exhaust, or no coolant circulation on that side. all of the burnt downs i've ever seen started at the top and burnt down! This is way new to me!
 
it was around 20 degrees out and i was about 5 min away from my house, sled warmed up and i was comming out of a corner and she went down. i was going around 25mph when she let go on the trail. good snow, not hot. what do you guys mean by piston wash? how do i measure that?
 
piston wash is the areas of the piston crown, that are washed free of oil and carbon. the extra fuel is what washes the oil and carbon off the piston crown, so if you are lean on fuel, the piston crown gets hot (cause the fuel is also a cooling agent), and the oil has a chance to burn to the piston crown, instead of being washed off from the extra fuel, w/safe jetting. you know what i mean? if you were @ 25mph, you would have been on the pilots and needles and if your pilots were a little bit plugged, that would cause a lean hot condition and then w/being on the needles a bit for a while, would also cause high temps, combined w/the hot viper timing and then things go boom.
 
in your last picture, named "other pistons.jpg", you can see those 2 little shinny wash marks on the piston crown, on the intake side of the piston. see what i'm talking about? i would like to see that wash area doubled, from what you currently have. you should have wash marks about the size of your pinky nail. now notice that the center and mag don't have that? you need that, to be safe now a days.
 
I put some gas in it the other day i got from my buddy and he just told me that it was 89 octane. i did not re fuel after that. i was actually on my way to the gas station. how do i fix the lean? put bigger pilots in it?
 
the 89 octane, i would bet had the ethanol in it, which is what did it. if you would of had gas w/no ethanol in it, you would have been fine most likely.
 
if you plan on running 87 or 89 octane w/ethanol, run 157.5 mains, stock needles, stock pilots, and 2 turns on fuel screws.

if you plan on running 93 octane w/o ethanol, then i would run the stock jetting.

you can try fattening up the midrange by 1/2 clip position, which would be 1 washer on top and bottom of the clip, while its in the 4th groove (2nd closest to the pointy end of needle), but i think your going to get too gurgly on the bottom and leading into the midrange.
 
mopar1rules:: it is gurgly on the bottom end now. i will run 93 octane or higher for now on and i will leave my sled to stock settings now. right now i am 2-1/8 turns out on the fuel screws and i still have the idle hang for about 25 sec.
 
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