Potentially controversial fuel question

[1_v8_merc]

My 750ec calls for 90oct or higher, preferably unleaded or low-lead.
Factory compression says 8.7:1

I always run 93, since it was rebuilt and advanced. Sometimes I will run 100LL, bike runs perfectly fine on it.

[7981GS]

My 10.7:1 and 10.75:1 bikes don't like the 91 octane p*ss much either and require a 100 octane mixer during the summer months.
They didn't have a problem running on the 92 octane that we USED to be able to buy around here a few years ago!

Eric

[gearhead13]

My 750ec calls for 90oct or higher, preferably unleaded or low-lead.
Factory compression says 8.7:1

I always run 93, since it was rebuilt and advanced. Sometimes I will run 100LL, bike runs perfectly fine on it.

You have leaded gas there Havent had that stuff here for decades

[gearhead13]

They say a fool and his money are soon parted!

Id rather pay a few cents more per litre than ruin my expensive engine

[bccap]

1100G manual with 8.8:1 compression ratio...



GSX1100G manual with 10.0:1 compression ratio...



What ever you choose to put in your tanks, doesn't effect the longevity of my engines.


Eric

Just found it in my service manual. It says 89 or better. So I'm going to try to stick with Chevron 94 which is ethanol free as well. I hate paying for premium that has ethanol. Chevron is still one of the ones that doesn't charge for air either. I wonder how many of these little details are allowing Chevron to steal market share.

[JimmyR]

Interesting stuff guys. FWIW I have put some 95 in my bike now (instead of 92) and yes it has made a significant difference. BTW I have RS36s - sorry for the typo.

The other thing which has made an enormous difference was to change the mains from 127.5 to 130. Everybody tells me that the mains only affect the last 1/4 of throttle on flatslide carbies and will have no effect on idle and just off idle. Well switching to 130 mains has let me drop two sizes in pilots, and I may even down one more. My test ride yesterday was a revelation - so smooth! It was wonderful. It was good before but now it's even better.

My plugs afterwards were still covered in a very fine layer of black but the tips are starting to go biscuit colour, so I am on the right track. Carb synch is almost perfect. The carbs are all within millimetres of each other on my carbtune. Pretty happy with that!

[hampshirehog]

I can understand that part of it, but can not verify with personal experience.

With three separate vehicles, my 850, my Wing and my van, I have tracked mileage and overall performance using various fuels. I have run a minimum of three tanksfuls of "regular" gas, noted the mileage and overall performance. Then I ran at least three tanks of "premium" fuel and noted any difference. Then I ran at least three tanks of "no ethanol" gas and noted the difference. The "premium" gas was not "ethanol-free", the "no ethanol" gas was "regular", 87 octane.

I keep a logbook in the van, so I can make notes about such stuff. In reviewing my notes, I can not find any differenece in gas mileage or performance, only that my wallet was a bit lighter, as both the "premium" gas and the "no ethanol" gas were about 20 cents more per gallon.

Maybe I happen to have three of those "one in a million" vehicles that are not affected by ethanol, but I will continue to use the cheapest stuff that will do the job.

.

Steve we can only get ethanol free petrol in a higher octane fuel (it's only 97 instead of 95 so not a biggy).

The issues the guys using it are trying to avoid are:

If you are a show rider and leave your bike parked up for weeks on end the ethanol separates out in to water and potentially rusts the tank at worst or clogs the carbs at best.

Ethanol eats some of the rubber components used in the fuel to engine route.

Ethanol eats some tank sealants. There's a few people on here who have had problems with this recently and although it's ok to point out that they should have used a better sealant often the case is when the sealant was used 10 years ago before the issue was even thought about.

Fibreglass tanks, such as on a Spitty or even my little Bultaco Sherpa just love to dissolve themselves in ethanol. The Bultaco tank contained regular when I got it - or rather it and the carb contained syrup!

I bought some BP Ultimate yesterday for the Bultaco. It was 7 pence a litre more expensive than regular so the price is not worth bothering about.

[themess]

I can understand that part of it, but can not verify with personal experience.

....
I keep a logbook in the van, so I can make notes about such stuff. In reviewing my notes, I can not find any differenece in gas mileage or performance, only that my wallet was a bit lighter, as both the "premium" gas and the "no ethanol" gas were about 20 cents more per gallon.

Maybe I happen to have three of those "one in a million" vehicles that are not affected by ethanol, but I will continue to use the cheapest stuff that will do the job. .

Thanks for posting this! Useful data.

You have leaded gas there Havent had that stuff here for decades

Leaded gas is bad for modern engines, and it wasn't very good for old engines, either.

[jimb12]

7981GS, the figures that you're posting in the manual are for Research Octane or RON. Those are the figures that the Aussies use apparently. Here in the USA we have PON which is the average of RON and MON ratings. The MON test is tougher than the RON and therefore produces lower numbers than the RON does. This is why our numbers on the pump are lower for the same grade of gasoline.