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Ethonol Gas

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Well I have a crf that is getting brought up to date as we speak because the last time I was at the track I doubled in doubled out and very softly landed and boink the tack tack tack of something in my crank area. Im having a bunch of updates put on the bike while she is torn down,but anyway the point I am trying to make is that there seems to be a rash of 4 strokes in the shop waiting to have the crank replaced. 99.999% of these bikes have been running on high octane pump gas. A local mx shop in the area has discussed the fact that the new gas we are buying is doing some major damage to our bikes. When I get her back I will put nothing but race gas in her and the same for my sons cr 125. Just a little bit of info I was given about the gas situation. How many of you are replacing your crank bearing right now and use pump gas?:applause:

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Did the guy at the shop explain why he felt the gas was the cause of a bottom end issue? Usually, a bottom end issue is do to either just wearing out from use or a lubrication issue. Since we are talking about a 4-stroke that does not rely on the gas to carry the oil through the bottom end like a 2-stroke with pre-mix, I'm not seeing how the type of fuel you use can affect the bottom end.

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I always have trouble with these kind of reports. Usually on several levels. I'm not saying they are wrong, I just don't understand it.

The first is that ethanol in pump gas is bad. It is oxygenated fuel. Here in the US, we are phasing out MTBE and going with ethanol instead. People say "it's bad." Now for race fuel oxygenated people say "It's good." I don't know what they use, but it almost for sure either ethanol or MTBE. It's either good or bad.

Perhaps it is just the octane that is not good enough. Not ever gas station is honest and perhaps they are not really pumping premium. One thing that I do know for sure. On those single hose pumps you get a hose full of whaterver the last customer bought. Usually it is regular. So at first you get 87 octane, and not premium. If you are just topping off you bike tank it could be a lot of 87 mixed in with the high octane.

The fuel related problems that I am used to seeing are piston related issues. I'm sure that I could be wrong here, but I always thought that melted pistons usually happen first with pinging, not worn out crank bearings.

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I will have to redisscuss this with him but the corn additives from what I understand clog jets and can cause a crattering effect to other parts of the engine which rely on effiecient gas distribution. Im no mechanic by far but am hearing the back up of bikes with same issues.

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I always have trouble with these kind of reports. Usually on several levels. I'm not saying they are wrong, I just don't understand it.

The first is that ethanol in pump gas is bad. It is oxygenated fuel. Here in the US, we are phasing out MTBE and going with ethanol instead. People say "it's bad." Now for race fuel oxygenated people say "It's good." I don't know what they use, but it almost for sure either ethanol or MTBE. It's either good or bad.

Perhaps it is just the octane that is not good enough. Not ever gas station is honest and perhaps they are not really pumping premium. One thing that I do know for sure. On those single hose pumps you get a hose full of whaterver the last customer bought. Usually it is regular. So at first you get 87 octane, and not premium. If you are just topping off you bike tank it could be a lot of 87 mixed in with the high octane.

The fuel related problems that I am used to seeing are piston related issues. I'm sure that I could be wrong here, but I always thought that melted pistons usually happen first with pinging, not worn out crank bearings.

Now that is interesting...

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If pinging is the cause, ethanol is not the suspect. Alcohols in general are low energy fuels, and have been known to cause corrosion of certain parts within the fuel system, but in the percentage legally allowed in pump fuels for single fuel gasoline engines, they're fairly harmless. Fairly useless, too, but that's another story.

As far as pinging goes, ethanol itself has a very high equivalent octane value, as do most alcohols. If, however, you are borderline lean, a switch to a highly oxygenated fuel might cause you some trouble, but still most likely would not lead directly to crank bearing failure.

I'd say that your problem is either related to your oil, or to the time on the bike, and that his problem is he believes in fairy tales.

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I will have to redisscuss this with him but the corn additives from what I understand clog jets and can cause a crattering effect to other parts of the engine which rely on effiecient gas distribution. Im no mechanic by far but am hearing the back up of bikes with same issues.

Maybe he is drinking the corn squeezings instead of putting in the tank :applause: How would a clogged jet affect the crank or the bottom end?

Some people just spout off without thinking.

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Ok here is some more insight that I just saw first hand with my entire engine torn down again. 15 hours on the head and new valves,massive carbonization and still valve cupping after 15 hours. This is causing the piston and pin to were prematurely hence the crank seizure. Bottom line the bikes high rpms are are burning up the piston and everything down from there. I believe the statement about the leftover gas in the pump hoses is very insiteful,as per my last fill up I pulled up right to the pump and filled it up with what I thought was 93 octane.

Say it I :applause: up my bike say it!!!

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I hate to say it but,..........

You should have bought a Yamaha.

Just kidding. I extremely doubt that the amount of 87 octane left in the hose is going to cause this problem. MAYBE over a very long period of time, if you repeatedly were running 87, than you would get detonation issues.

I'm wondering....do you get gas from the same place all the time?? Maybe the station is the cause??? I'd definately see what is going on before this re-occurs.

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I went to an ethonol plant on a school trip and I really don't see how it could hurt your bike it is just denatured 200 proof alcohol (I got to smell a sample:eek: ). The plant smelled like beer to though lol

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Poor fuel causing crank bearing failure on a 4 stroke does not make a whole lot of sense to me. I could understand that IF it was a 2 stroke, as the fuel/oil/air mix DOES go into the crank area for lubrication. Poor fuel can cause detonation and overheating issues, which WILL kill your valves. The amount of 87 octane fuel you get from the hose (when the previous customer has filled up with 87 octane) IMO isn't enough to cause engine damage when mixed with 91-93 octane fuel.

What kind of oil are you using on the engine side of the bike? A bad or improper oil may be causing both your crank and valve troubles. Of course, you may also have just gotten bad bearings and valves when the bike was new (it happens, even to Honda).

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15 hours on the head and new valves,massive carbonization and still valve cupping after 15 hours. This is causing the piston and pin to were prematurely hence the crank seizure. Bottom line the bikes high rpms are are burning up the piston and everything down from there. Say it I :applause: up my bike say it!!!

Unless the rings and cylinder wall are messed up thereby allowing fuel/blowby to get by and into the crankcaseto ruin the oil, that is NOT a cause of crankbearing failure.

Low octane fuel does, however, cause your carbon buildup:

One source is excessive carbon buildup. That means nothing is wrong and the engine simply needs a good cleaning, ON THE INSIDE. The reason for the excessive carbon could be due to an oil consumption problem, either leaky valve seals or worn piston rings. Either way, the head needs to be removed to solve the root cause, the can be decarboned at the same time. An engine is normally good at burning away carbon on it's own. The problem could also be due to mal-adjusted carbs or a dirty air filter causing the engine to run way to rich. In no case does the pinging from carbon cause engine damage.

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....In no case does the pinging from carbon cause engine damage.

"Pinging" is the abnormal combustion phenomenon called detonation. It's also known as knock, spark knock, etc. It doesn't matter if it's from excessive compression caused by carbon build up, low octane fuel, too much ignition advance, or any other cause. There aren't different kinds of deto for different causes, just different causes for the same deto.

Deto can cause engine damage including crank bearing failure. In most cases careful (skilled!) diagnosis of the piston and plug should reveal if any deto had been taking place. But I would think that deto that is strong enough to damage a crank bearing would be clearly audible to the rider.

Deto is when end gasses in the combustion chamber explode (detonate) rather than burn (deflagrate). The pressure wave sent out by detonating end gas moves at local supersonic speeds--much faster than the normal burn of deflagration. The piston can't come anywere close to moving down fast enough to absorb this pressure. The sound we hear that signals deto is taking place is these waves smacking into the sufaces of the combustion chamber. The engine "pings" or "knocks" audibly; the metal actually resonates.

Deto is like hitting the top of your piston with a ball pean hammer while normal combustion (deflagration) is like placing a heavy weight on it.

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Some wrong information as there actually are different kinds of detonation.

To start, Run on knock is different than other pinging.

Detonation from carbon build-up produces a different detonation pattern than detanonation from high cylinder temps. The sound is the same, but the wave fronts are different.

Furthermore it's DIFFERENT because pinging from carbon build-up will NOT damage your engine, but pinging/detonation from excessive cylinder temps will.

All pinging is not the same with different causes. The sound 'may' be the same, but the wave fronts and causes are different and may nor may not cause engine damage.

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When there is ethanol in the gas, the jetting must be adjusted.

In CT when they went to gasohol (legal def., at least 10% ethanol), I had to richen the mixture by 14% for the 10% ethanol blend.

The more ethanol, the leaner your jetting will be, the more you have to richen it up.

Dave

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Some wrong information as there actually are different kinds of detonation.

To start, Run on knock is different than other pinging.

Detonation from carbon build-up produces a different detonation pattern than detanonation from high cylinder temps. The sound is the same, but the wave fronts are different.

Furthermore it's DIFFERENT because pinging from carbon build-up will NOT damage your engine, but pinging/detonation from excessive cylinder temps will.

All pinging is not the same with different causes. The sound 'may' be the same, but the wave fronts and causes are different and may nor may not cause engine damage.

This is interesting. If I'm wrong I want to know.

Where can I learn more about this? Post or PM. Thanks.

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