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Two seasons I spent a lot of time trying to find why Harry's sled suffered a failure (xflipper) while his buddy's sled survived from fuelling at the same pump. The piston showed that it had melted the exhaust side. The thank was emptied dry and no water was found, but no water content test was done.

Since then I took an interest in gas for two strokes and found odd stories that I found difficult to believe. A Ski-Doo ETEC failing while a Polaris Cleanfire was showing a significant decrease in power from the same gas station? There were many such stories last season that didn't make much sense. Could this really be happening while our cars or trucks rarely show such problems?

It wasn't until almost a year later with subsequent failures that that Peter from That Girl Racing made it clear that there was nothing magical about these failures. The exhaust end of the piston crown melting showed clear signs of detonation. I didn't buy this at first, but failure after failure the evidence grew and well.....this is where we are at.

This is what bad gas can look like, but it can also look like good gas and smell like a problems as you will read later from the MachZ owner.

Food Tableware Ingredient Gas Dish


Recently, the following sleds that filled at the same gas station with Premium 93 suffered a failure or ran poorly. I took this information tonight so that you get the information as up to date as possible.

The failures start with the first sled that filled-up the most at this gas station, a Formula Z. It does not represent which sled is more prone to failure. This is just an approximate time line, and I got the most information possible. However it does show that few Two Strokes are protected against Bad Gas.

1st 1993 583 Formula Z SL
- Gas tank was near empty before fill-up
- Engine Failed

2nd 2013 Rush 800 RMK
- Gas tank level unknown
- Engine Failed

3rd 1998 Fomula 670
- Gas tank level unknown
- Engine Failed

4th 2006 MachZ 1000 SDI
- Gas tank 3/4 full
- Owner smelt stale gas
- Only filled 1/4 tank to full
- Survived all day
- Engine Failed the next day

5th 2010 Yamaha Nitro 4 stroke
- Started pinging
- Exhaust donut securing mechanism shrunk and got loose and began to make a rattling noise.
- Dealer emptied tank and ran new fuel.
- Problem solved with new gas with no failure

6th 2010 TNT 600
- Same owner as the MachZ
- Ran 80 km before owner made the connection with MachZ and other failures
- Tank was emptied
- Problem solved with new gas with no failure.
- 1 out of 2 survived, not bad?????
 

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While this last story was just recent, about a month ago a member on this forum informed me of a failure with his MachZ. One of the first questions I asked was were you riding with someone and did that person have trouble with his sled. It happened that he was riding with an 800 HO owner who suffered a loss of power shortly after fill-up which luckily did not end in a failure and ended with a simple engine stall.

Both sleds were filled with Premium 94 from Petro Canada.

Like Peter from That Girl Racing has tough me, nothing needs to be overly complicated. The injectors overheated from detonation, so it was obvious to me that they needed to be flow checked. We did and found a flow problem with the failed MAG side. The owner cleaned them, put new pistons, and now the engine is running again. Simple.

The part that is not so simple is the crankshaft Big End bearings have now suffered detonation.

Are we beginning to see how complicated the Big End bearing failures can get?
 

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Daag when I was in the sled business we got at least one sled at the start of every season with a last seasons gas failure. I preach to all my friends to siphon their tanks and start fresh every fall and don't rely on snake oil to magically fix it. One co worker actually laughed out loud and told me I was full of crap.....the next season he smoked a piston in his sons 500ss in the first mile of the year. People fail to understand these are high performance engines with little tolerance for inadequate octane. You don't hear of too many mid season bad gas failures but they do happen and word usually travels fast in the town where it was purchased.
 

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My friends 09 f8 just had some bad detonation. The sled broke a throttle cable. He dropped it off at a shop. They replaced the cable and when he got it back it wouldn't idle properly so I adjusted it so it would idle properly. They next day we went for a ride after about 50 miles he stopped to put fuel in his sled. I didn't need fuel. We went about 5 miles and we hit a field he felt a power fade. As he was pulling over the sled died. I pulled the plugs on the pto side and both of the plugs on the pto side had the ground straps hammered into the electrodes. I had him take a picture of it. I will post the picture today. Needless to say he's going to need a crank and a fresh set of pistons. It's amazing how easily it is to get bad gas. It was from a busy gas station too.
 

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Daag when I was in the sled business we got at least one sled at the start of every season with a last seasons gas failure. I preach to all my friends to siphon their tanks and start fresh every fall and don't rely on snake oil to magically fix it. One co worker actually laughed out loud and told me I was full of crap.....the next season he smoked a piston in his sons 500ss in the first mile of the year. People fail to understand these are high performance engines with little tolerance for inadequate octane. You don't hear of too many mid season bad gas failures but they do happen and word usually travels fast in the town where it was purchased.
I did the same thing to my Mach at the start of this season. I'd rather burn the sale funky gas thru my snowblower or even my truck than have one more variable in that sled engine.
 

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That is one nice thing about carrying a fuel caddy. If Im going out of the area I usually stop and fill it with some 110 and I can use it if I run out, or use it to spruce up a questionable fill. 2.8 gallons put half in a tank and top it off when I find good gas next
 

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You wouldn't drink last years milk, why would you let your sled drink last years gas? Treat the gas like milk, after about 3 weeks, it starts t get sour with the gas we get these days. I was terribly busy at the shop this summer with most problems due to having last years gas still in the tank. Should of seen some of the pistons I pulled out. Awful.
 

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Charles, it was 2 seasons ago when mine burnt that piston and my friends survived the gas fill and also towed me home with a passenger on the back of his sled. What I didn't mention is, the season prior to mine going down, his 800 ETEC blew up and we both filled up at the same station. using premium as always. About 2 miles after fill. His locked up, so he rocked the pto till it unlocked, started it up,running on 1 cyl went to drive it back locked up again.He kept unlocking it and this happened numerous times and he got it home. I wanted to go get my truck, but he was ticked off and drove it home. Took the top end off and what a mess. Mine looked mint compare to his.What has me shaking my head is how it was put back together. He picked up a used cylinder a set of those hyper SPI pistons never took the crank case apart, just washed the crankcase out with gas and blew it out with an air hose. It is still running to this day. I thought it would have taken out the bottom end by now. I suppose luck and a matter of time.
 

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Big bores and wide squish bands promote detontation. This plus ethanol fuel and inconsistent compressions ratios are a detonation episode waiting to happen.
 

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