when it comes to gas how low is too low on octane?

[Anonymous]

So here is my next question for the masses:
I know that if you run too high octane gas you will burn too hot and you can burn you valves. You can tell that you are burning too hot by your sparks and if your exhaust pipes are turning blue. Well I havent cheacked my sparks yet ( thought it is on my list of things to do) but my down pipes have been turning blue so I was told I am burning too hot. I was running 93 octane but I kicked it down to 89 when I was told 93 realy was too high for a '79 (btw I have a '79 GS1000E). Well my pipes were still seeming to continue to turn blue-er and I have been having tremendous emounts of heat comming off the block. This is my first summer of realy riding so I dont know how much of the heat thing is normal. I have dropped the gas now down to 87 octane (regular) and some of the heat feels to have gone down along with a little bit of power but it still has no problem flying up very steap hills and I am a VERY big boy. But I dont know what can happen from me burning gas too low in octane.....any one know? :?:

 

[jimcor]

87 octane is just fine for your bike. Anything higher is just a waste of money. That's all I run in both my bikes. Rule of thumb, if it doen't knock or ping, everything is fine.

That loss of power was all in your imagination. :wink:

 

[DMPLATT]

My Factory Manual says to run 89 octane. I used to run Super in my bikes. Now I realize it's not necessary. I run 89 and all is well. Only a few more cents than 87, so I'll go by what the manual says.

 

[rphillips]

I've never heard that 93 octane will run too hot, nor harm anything, just waste money. I wouldn't recommend 110 octane airplane or racing fuel, but I don't see 93 harming a thing. Usually blue pipes mean too rich or too lean.

 

[jimcor]

No guys. Blue chrome means it is most probably an aftermarket exhaust. Single walled and less than stellar plating. Your stock exhaust will blue too, and they are doubled walled at 'hot spots'. It does not neccessarily mean you are running too lean, and hot. Chrome blues, simple as that. The new Harley and other cruiser pipes are running a big chrome beauty pipe around the true exhaust pipe so it doesn't get hot or blue.

 

[rphillips]

I agree, the aftermarkets will discolor a lot quicker than the double wall stock pipes. But a good quality aftermarket pipe on a good tuned & jetted bike, may turn a slight gold color, & never turn blue. Stock pipes on a bike that is too rich or too lean will also turn blue & purple, but certainly not as quick as an aftermarket. In my opinion, jetting is the #1 cause of blueing, and vote quality of pipe & chrome the #2 cause. Just my opinion

 

[Anonymous]

Take it from someone who used to be a marketing rep for a major oil company ... The only thing that octane measures is your engines ability to resist knock. As stated above, if it doesn't knock you're fine. I don't believe higher octane gas would have anything to do with how hot the gas burns.

Check out the link below, this is from the Fedewral Trade Commision site:

http://www.ftc.gov/bcp/conline/pubs/autos/octane.htm

 

[Hoomgar]

Higher octanes will run cooler if anything at all. Run what is recommended. If your bike doesn't run good on it then go up a grade until it does. This is an indicator of engine troubles though and you should look into that. For a 78, 79, 80 or whatever old GS1000 87 octane is what you should run. And it should run fine. Higher octane will never hurt it and is a cleaner fuel too so if you want to pony the extra few cents it wont hurt a thing but it isn't needed.

There are many opinions on this subject here and all based on experience. I am afraid you?re going to have to sort this one out for yourself. The guys on this forum cannot agree on this subject or motor oil for that mater. Chain vs shaft is another issue entirely

 

[gspaul]

Bikes come with ...............CHAIN'S !

 

[jimcor]

Ah now, we all agree gas and oil are good. But... your higher octane fuels have additives that allow them to burn slower. More additives, more deposits, not a cleaner fuel. Although some higher octane fuels do have a detergent that helps to supposedly keep fuel injectors clean. :twisted:

 

[Hoomgar]

Ah now, we all agree gas and oil are good. But... your higher octane fuels have additives that allow them to burn slower. More additives, more deposits, not a cleaner fuel. Although some higher octane fuels do have a detergent that helps to supposedly keep fuel injectors clean. :twisted:

See what I mean? And Jim is one of the good guys!!! 8O :roll:

Wait until the forcefully opinionated ones show up! :lol: :lol: :lol: :lol:

 

[Anonymous]

Well nice to see we have all come to a conclusion. :roll: the person that told me that running too high octane could burn out your valve seals has been riding for over 30 years and said he burned them out in one of his older bikes because of the gas. But I am gonna just keep riding around and if something brakes...well then I guess I can fix it or get a new bike lol :twisted:
now that I am trying to hear my engine running wierd I am not sure if any of the noise is new or old. I think it is making a new sound on the lower octane but it is only at high speed ( over 60 mph) and it may have been ther before I guess I will just keep guessing lol Thanks guys

 

[mark]

Just to add to the confusion, my understanding is that what could burn out valves in older bikes is the unleaded fuel, it wasn't an octane issue. Older bikes needed leaded gas to cool the valves and were designed with somewhat "softer valves". Valves were redesigned with the onset of unleaded gas.

 

[jimcor]

Just to add to the confusion, my understanding is that what could burn out valves in older bikes is the unleaded fuel, it wasn't an octane issue. Older bikes needed leaded gas to cool the valves and were designed with somewhat "softer valves". Valves were redesigned with the onset of unleaded gas.

The lead in fuel didn't cool the valves it lubricated them. But of course they ran cooler because of less friction. So I guess, in the end we're talking about the same thing.

Speedie, I've been riding 8 years longer than your 30 year riding pard and too high an octane burning out valve seals is...Hogwash. :lol:

 

[mcycle-nut]

Just to add to the confusion, my understanding is that what could burn out valves in older bikes is the unleaded fuel, it wasn't an octane issue. Older bikes needed leaded gas to cool the valves and were designed with somewhat "softer valves". Valves were redesigned with the onset of unleaded gas.

The lead in fuel didn't cool the valves it lubricated them. But of course they ran cooler because of less friction. So I guess, in the end we're talking about the same thing.

Speedie, I've been riding 8 years longer than your 30 year riding pard and too high an octane burning out valve seals is...Hogwash. :lol:

I think his friend is confused. If you ran unleaded fuel in older vehicles (50's. 60's) you could harm your valve SEATS, not seals.

 

[LW_Icarus]

yet another fuel observation-turbo blue or cam2 will sink neoprene floats.and sometimes harm coatings in the carb. Ive put cam2 in a perfectly good motorcycle and had a gas leaking mess overnight. fuel additives will sometimes do the same, although I believe the formulas are better now.

but after some modifications and retuning my old bikes loved race gas. back then I was feeling ripped off paying 2.30 a gallon for the stuff lol.

back to the original posters observation of a hot running bike, and blue pipes, if it really is ultra hot(which could be verified with a raytek temp gun) then you are leaning out. 14.7:1 I believe is the ideal mixture to combust gas/air, anything leaner (more air) will run exponentially hotter.

look at your intake boots. probably the most likely cause of a vacuum leak. a little gumout sprayed around em with the engine running will quickly identify leaks.

 

[gsBert]

oh gawd, dont tell me were talking about octane again.

i'll talk about the gas first, then about your running hot problem (the two are not related in any way)

first of all speedie, because your buddy's been riding 30 years doesnt mean he knows squat about engines, chemistry, or motorcycles. (heck my dad's been riding a long time and when i told him about counter-steering he called me a liar)

if you're running hot, it had nothing to do with octane. it has to do with mixture. (air/fuel ratio, just like when you use an oxyacetylene torch, more oxygen, more heat, less oxy, less heat)

about octane:
you should use the lowest octane rating gas possible, that is use 87 unless your engine pings, and if it pings, make sure its not because off timing or other stuff.
if you've been running super all along you might have carbon deposits in your combustion chambers that could cause hot spots and make it ping on regular gas unless you clean your combustion chambers.

here's how to clean the engine out without taking it apart:
- warm up your engine
- remove the air filters or air box and idle the engine fastish 2500 rpms
- use a spray bottle to spray fine water mist into your carb intakes
- you'll likely get lots of smoke and a bit of hesitation, dont worry, no harm will come of it

here's what it does:
the super youve been running doesnt all combust because it's well, too high octane for your engine (hight octane=less combustible)
the unburnt gas caused carbon deposits as i've said.
when the water mist hits your combustion chamber walls it flashes to a boil and detaches those deposits (they'll spit out your exhaust)

run about 1/8 cup through each cylinder that way and your engine should be cleanish. you can now run on regular.

about running hot now:
the pipes turn blue, its a fact of life. the way of telling if your engine is running too hot is to remove the plugs and stick your finger in, just kidding.
plugs should be a nice tan color, if they are white, you're running too hot, which means your carbs are too lean. if they're black you're running too rich which means your carbs are too rich and you shouldnt be getting your engine too hot unless you have an oiling problem (your bike is oil-cooled) or a very dirty engine (your bike is air-cooled also). also different plugs have differnet heat ranges. make sure your plugs are what came stock on your bike (ask a bike shop for the proper heat range) and gapped properly.

different people will have different opinions, but if you wanted information, you just got it.
do things in this order:
- give your engine a good wash (make sure the cooling fins are clear of dirt)
- make sure there are no intake vacuum leaks anywhere (listen with a hose)
- decarbonize your engine as described above
- check the timing
- check the sparkplugs
- get an oil change (how many miles you got?, i like using 20-w50)
- rejet your carbs if necessary to compensate for the potentially lean condition

 

[duaneage]

Octane is the ability of the gasoline to resist detonation. Period.
The combustion takes place in .003 of a second regardless of octane. High octane gas does not burn faster or slower than low octane gas. It does not carbon a head, dirty airfilters, weak spark, oil burning and poor jetting cause carbon buildup, not super unleaded.

While true that too high an octane is a wste of money, at 80 cents a tank more I prefer Super unleaded because the bike will not ping, ever, under load in the summertime.

 

[Anonymous]

Octane is the ability of the gasoline to resist detonation. Period.

That's the way I understand it as well. Detonation = pre-ignition. Unless I'm mistaken, higher compression tends to encourage pre-ignition, and higher octane allows the fuel to resist this in order to fire at the right time.

Perhaps the faster/slower idea is a slightly mis-stated version of sooner/later.

Willing to stand corrected,
Steve

p.s. I've been pissing for over 30 years, but that doesn't mean I know how kidneys work.

 

[duaneage]

Octane is the ability of the gasoline to resist detonation. Period.

That's the way I understand it as well. Detonation = pre-ignition. Unless I'm mistaken, higher compression tends to encourage pre-ignition, and higher octane allows the fuel to resist this in order to fire at the right time.

Perhaps the faster/slower idea is a slightly mis-stated version of sooner/later.

Correct a mundo

Flame travel speed is the same regardless of octane, no harm is done with extra quality. pre-ignition cannot always be heard by the rider but the connecting rods and bearings will feel it neverless.