Problem switching from 87 octane to 93 in a 372

[Marc]

Standard preface: I did a quick search on this and couldn't find anything pertinent to my specific situation.

I've been running my 372 for the last three years on 87 octane and synth 2 cycle oil. It was tuned for that, ran fine. Over the last year, I had heard from a few reputable sources one is better of running 93. So my last 2.5 gallon can I fill with 93 and the same synth oil from my local Husky dealer.

The first time I run the saw with the new gas it takes more pulls than normal to start. Once it does, it doesn't want to keep running. I finally get it warmed up after several starts and it runs long enough for me to re adjust the L screw and the idle speed to where it will idle, but not smoothly, and the idle speed is really a tick higher than it should be. And it's kinda on the edge of stalling out. It runs like normal in a cut at WOT, but it still won't run consistently- i.e. I'll hit the throttle after it has been sitting at adle for a minute and it stalls immediately. Sometimes it still just stalls at idle. It normally starts with one pull once it's warm but now it fights me every time. I pulled the plug, it looked normal. Banged out the air filter, but there wasn't much in it.

It has to have something to do with the fuel. I haven't tried emptying the tank on the saw and looking at the fuel filter, but could there be any problem specific to swtiching over to 93? I'd hate to waste 2.5 gallons of premix, but if I need to, I can dump it into one of the old tractors and start fresh.

Thanks in advance for any ideas.

 

[nate cutter]

Do you know what your compresion is? If it's on the low side it will not be happy with 93. The other posibility that the 93 you got was old.

 

[Marc]

Do you know what your compresion is? If it's on the low side it will not be happy with 93. The other posibility that the 93 you got was old.

I tested it when I got the saw and it was around 140 psi. I haven't put that many hours on it since then. That was just a few years ago...

 

[jus2fat]

Your problem is likely just old gas.

Not many folks buy premium gas..especially with gas sooo high.

So it just sits in the tank at the station...forever..!!

Just switch back to the 87 octane and then you'll be getting 'fresh' gas..!!

J2F

 

[Marc]

Your problem is likely just old gas.

Not many folks buy premium gas..especially with gas sooo high.

So it just sits in the tank at the station...forever..!!

Just switch back to the 87 octane and then you'll be getting 'fresh' gas..!!

J2F

Cool, thanks for the help.

Well, the ol Massey is gonna get a little extra lubrication from this batch, looks like.

 

[Walt41]

Your problem is likely just old gas.

Not many folks buy premium gas..especially with gas sooo high.

So it just sits in the tank at the station...forever..!!

Just switch back to the 87 octane and then you'll be getting 'fresh' gas..!!

J2F

Exactly right, for you guys wanting higher octane I'd recommend going to an additive. Jr had this problem last week with his Corvette, went and got 5gals of "fresh" 93 and now it is running like it is full of water.

 

[tommyus4]

I have the exact same problem. I tuned it the exact way you did too with the same results.

I went and got new 93 etc and it's better but still off. I just realized the error of my ways. Same gas station.

I never thought about the fact that most don't use 93. My friend only gets his at Shell. I was going to an independant which is closest to my house.

Thanks for the post and responses.

ps Would mixing 93 and 87 be okay? I do that for my Hondas over the years as you should get 90 instead of 89 at a few cents a gallon cheaper. A pain but I hate the fuel mix surcharge.

 

[tommyus4]

Exactly right, for you guys wanting higher octane I'd recommend going to an additive. Jr had this problem last week with his Corvette, went and got 5gals of "fresh" 93 and now it is running like it is full of water.

Walt, any additives you recommend ? Or is the octane thing over rated? I will go read some threads on it. I'm sure it's been a hot topic before. Thanks, in advance.

 

[Walt41]

Walt, any additives you recommend ? Or is the octane thing over rated? I will go read some threads on it. I'm sure it's been a hot topic before. Thanks, in advance.

In the hot cars we use Fireball, for saws I just add one large plastic medical liquid dispenser of whatever booster was on sale to a gallon of mix, my son works at Autozone, so from time to time we get free samples to test from the reps.

 

[Marc]

In the hot cars we use Fireball, for saws I just add one large plastic medical liquid dispenser of whatever booster was on sale to a gallon of mix, my son works at Autozone, so from time to time we get free samples to test from the reps.

Nice. My father was a sales manager for Castrol Industrial so we used to get a lot of stuff for free... hydraulic fluid, grease, oil, etc.

Althought because it was all industrial, the standard sample size of anything was a 5 gallon drum. So yeah. We're still working on the same drum of roller chain grease from like 15 years ago.

 

[Marc]

I have the exact same problem. I tuned it the exact way you did too with the same results.

I went and got new 93 etc and it's better but still off. I just realized the error of my ways. Same gas station.

I never thought about the fact that most don't use 93. My friend only gets his at Shell. I was going to an independant which is closest to my house.

Thanks for the post and responses.

ps Would mixing 93 and 87 be okay? I do that for my Hondas over the years as you should get 90 instead of 89 at a few cents a gallon cheaper. A pain but I hate the fuel mix surcharge.

Thanks for posting Tommy, glad I'm not the only one with the issue.

 

[Ambull]

The difference in octane rating should not cause all these problems. Either the 93 gas is bad, or something has changed in the saw.

If you do not run the saw a lot, the best thing for it is to get Aviation Fuel 100LL. It is 100 octane low lead, and it has no ethanol in it. It has a 2+ year shelf life, and only costs a little more than the 93 octane. It can be found at most small airports.

When on this gas, there is no need to drain out the tank during the off season. It will not varnish up, and it will not dry out the rubber components in the fuel system. I run it in all my saws, and it has worked perfectly for me.

 

[B_Pike82]

Walt, any additives you recommend ? Or is the octane thing over rated? I will go read some threads on it. I'm sure it's been a hot topic before. Thanks, in advance.

Those octane boosters are a waste of money. When the bottle says it will boost octane 2 points its doesnt mean 87 octane gets boosted to 89 it means 87 gets boost to 87.2! U would need to buy some super concentrated type that can boost 20 points to get 89 out of 87. The strongest id seen is 10 points but that was years ago so might be higher stuff now. If ur brave u can do what I used to do on my go-kart and dirt bike as a teen and mix some tulene and miniral spirits in some pump gas to make ur own race fuel. lol but i would try that on a disposible saw first.

Also higher octane is harder to burn thats why performance cars need it to prevebt pre-ignition so as long as your motor stays cooler and ur not get any detonation u would probably be better off with ur lower octane u been using. I see alot of teens putting in 93 in there mommas honda accord thinking there race car driver when in fact they are just spending more money on fuel thats not gonnaa burn completely thus making less power and worse fuel economy because there motor aint tuned for it.

Id see if u could get a hotter plug to help ignite the higher octane fuel and then if u need to run the lower stuff swap the colder plug in. Also check ur ignition coil to make sure its up to snuff. I would think reason why the higher octane runs fine under load or at higher revs is because motor is at higher temp under load so to help ignite it.

 

[Eecho]

Try putting a hot plug in the saw first lower octanes burn hotterand vice versa. Could very well be you have weak spark . 93 is prevention against ethanol by lowering cylinder temps in case of phase separation that occurs with corn gas. The best bet is always look up on pure gas dot whatever and find real gas or buy tru fuel or motomix for no storing issues.

 

[tommyus4]

I wasn't thinking additives as in STP or whatever allegedly boosts power/ octane. I was thinking more like a carb cleaner for whatever damage the gas did.

I know about the octane being a waste if a car is tuned for 87. Honda has recommended 89 since forever and recently justs suggests it but says 87 is okay.

And lastly, I did pick up the Motomix since my last post. I gotta know if it's the gas. If it works, I will go over to the local airport.

Thanks for the answers and hopefully Marc's problem and mine are gas related. Otherwise, something in the saw did in fact change. Thanks all.

 

[Boleclimber]

From previous work experience, running 87 octane in a chainsaw is a bad idea. The reason the saw did not run well switching form 87 to 93 is because the carburetor needed to be readjusted.

I only run 93 Octane in all my saws. I would shut down for the day before I put 87 Octane in any chainsaw.

 

[dingeryote]

In my 372 and other saws, I have to richen things up if I run Marathon or Shell 92, or they act as you described.
Usually just a quarter turn or less on each end. It's worse in winter when it's good and cold, and the little 200T will have snit fits.


Stay safe!
Dingeryote

 

[Sabertooth]

Just always use premium gas to begin with.

Regular or silver isn't good for 2 stroke anymore anyway.

 

[Jtheo]

I run 93 in the 372 and all my saws. No problems with it, but they were tuned on 93.

I do get ethanol free.

 

[tommyus4]

Update on mine:

Yesterday: I put the motomix in and it idled without shutting off. (Yay).
Then I revved it a bit. Then I let it idle some more. I cut one cookie and let it idle some more and it died. Thrilled with that:msp_thumbup: but I had no time for anything else.

Today: I warmed it up and let it idle for about 10 minutes. I then tuned it to the best of my novice ability. Just the low and the throttle. Cut a few cookies. Let it idle and it was fine.

Zero chance I use Motomix exclusively so I will try out other gas stations but will probably try the local airport or wherever I can get the non-ethanol.

<font size=5>Thank You </font size=5>for the responses. Much appreciated. I hope you have similar results Marc.