Was filling up my ute at the local BP petrol station and I noticed a sign on the bowser with the 98RON fuel (premium high octane here). The sign said, "BP Ultimate, up to ten times the cleaning power of regular fuel". What, ten times more detergent! I hope not. Maybe just stronger detergents.
I have worked on quite a few carbed bikes over the last couple of years that have had their carbs clagged from modern fuels with their additives designed to clean injectors at high pressure, but which cause problems for carbed bikes running at gravity to 3-4psi fuel pressure.
The extra $$$ for higher octane and premium fuels with their extra detergents and additives appears ime to pay for clogged pilot jets, gooped float needles and waxy deposits. This causes motors to be starved of fuel at lower revs and hard or no starting and then there is the carb flooding from float needles kept open from waxes and gel like residues. Two bikes, both VFR750s, had their float needles glued shut on some carbs and gooped open on others, so some cylinders flooded and others got starved really confusing the owners who tried to diagnose what was going on. The same for a Kwaka and a Monster. Had an old BSA 650 Lightning suffer terrible issues with flooding due to the Amal float needles not coping with the premium fuel the owner was using. Rebuilt the carbs and it seems to work (yes everything is available and better than original)!
If you don't need the extra octane then you are wasting your money, a truth not lost on many experienced members of the forum. But the issue for those with carbed bikes needing higher octane fuels due to high comp motors still remains.
The longer the fuel sits around the worse it gets so ride that bike or drain the bowls. A Briggs and Stratton tech told me fuel starts to deteriorate after two weeks according to a recent in service he attended. A Shell engineer I complained to admitted that fuel designed to clean injectors can clag carbs.
Use your manual tap if you have one and turn it off overnight. Use the lowest octane you can get away with as I'm guessing the fancy higher octane fuels have more additives/detergents as a marketing feature (don't blow up your bike though). My M900 with high comp needs our 98RON or else it will ping, so I'm careful which brands to use. Research which fuel brands have more goop in them and avoid them, after all, good old "straight" gasoline is great for washing parts. I use fuel stabilizer in my track bike because it sits around between thrashings (it's injected, but the fuel goes off). Expect occasional flooding and deal with it by turning your fuel tap off for 20 seconds and then back on again to reseat the float needles. Some run the bike at idle and tap the float bowl with the back of a screwdriver. If its bad you may be cleaning out the carbs. I drain the float bowls and run fuel through them into a container as a last resort before pulling them off and apart. Some use fuel cleaner in the tank to remove the goop and it may work if you're lucky. Float bowls use toilet technology so give that cistern a slap to stop the flooding!
If you like put the fancy stuff in your injected machines to keep the injectors clean. The manual for my Hyper1100Evo says 95-98 so I just run 98.
There have been a few threads on this topic, but seeing the sign on the bowser reminded me of the problem for people with older bikes. Worth a search with the search function.
Will FCRs fix the problem? :P
I still had occasional flooding with FCRs as I did with Mikuni CV 38s. A manual tap helped a lot, letting you clear the flooding and reseat the float needles on the go or at lights. The motor falters, then you look to your lower LHS and see the fuel coming out of the overflow (at lights, not at speed), so you turn the tap off for a 20 seconds or so and turn it back on. Usually does the job.
Use up the fuel in the bowls, turn off the tap at night, or drain the bowls and/or stabilize it if you won't be riding for a month.
One thing I've noticed for sure, the more you ride the less flooding seems to occur. If I haven't ridden the M900 for a week or two, it's more likely to occur.
I'm starting to think the rubber tips on new float needles take a bit of time to acclimatize to the fuel composition and the flooding subsides after happening a few times in the first week. Maybe the fuel softens the tips and they conform better to the float valve over time. Just guessing as I've rebuilt a few sets of carbs (different types) over the last year and seen that pattern. I expect it now.
FCRs fix the response problem ;D.
Great post Tony, with four pre '97 M900's I'll be keeping an eye on this post [popcorn]
I have blindly been using the BP Ultimate 98 RON fuel believing higher the octane the better!
Does it matter the higher octane fuels vs lower ones? I usually run cat pee gas but every now and then I'll throw a gallon of ethanol free "real gas". Whatever I have left over from the mower.
Used to be use of a higher octane than needed just caused an excessive lightening of your wallet. If using ethanol free fuel that is probably still true.
The additives used today for antiknock actually cause combustion chambers to get dirtier on our older low compression bikes.
Regular old regular is all a pre-696 2V monster needs. I suspect most of the newer bikes don't need all the octane Ducati says they do.
I guess the mfrs play it safe with octane recommendations to take into account variations in fuel quality. The manual says 95RON here for the old 9ish to 1 comp bikes, but I've seen manuals vary. I'm pretty sure I've also seen 91RON in a manual somewhere for the low comp bikes.
Curious what the 1100/1000 DS manuals say. I'm guessing 95RON. (The Evo manual says 95-98 as the comp went up a bit)
I've heard of people using regular in winter and the next octane up premium in summer in the lower comp bikes just as insurance in the hot weather. Most people tell me the 98RON makes the motor smoother. I've forgotten what my experience of it was in a low comp motor because I've been running high compression for a long time now. The downside of high comp is expensive fuel.
Great post Tony, with four pre '97 M900's I'll be keeping an eye on this post
I have blindly been using the BP Ultimate 98 RON fuel believing higher the octane the better!
Marty
I have a 97 M900 and live in Perth. In over 10 yrs I tried 98 once and had plug fouling issues. Reverted to 91 only. Absolutely no need to use anything higher for standard engines of that vintage. Never pinged.
Love your passion for these old models!
Al
The carbon problem with excessive octane in the us is due largely to ethanol. It does not atomize as well as gasoline, which is wht we have E85 instead of pure corn juice for our flex fuel cars in the US.
That has a lot to do with big oil and tax subsidies more than being E85. They've ran motors on (ethyl) alcohol for years in drag cars, boats, etc. The kick to that is it takes almost 2x as much fuel burning alcohol as it does gasoline but jetting and stuff is way trickier. And you can't run it on it for long periods of time. No lubricants and additives like gas.
Quote from: MotoPsycho on April 16, 2015, 06:33:59 PM
That has a lot to do with big oil and tax subsidies more than being E85. They've ran motors on (ethyl) alcohol for years in drag cars, boats, etc. The kick to that is it takes almost 2x as much fuel burning alcohol as it does gasoline but jetting and stuff is way trickier. And you can't run it on it for long periods of time. No lubricants and additives like gas.
Yes they have, but those vehicles don't have to start on a cool Sunday morning to get the family to church. In Brazil they learned pure ethanol does not work for the family sedan.
being in california with no option for alcohol-free gas i have grown to hate it with a passion.
unfortunately my motorcycles sit for fairly long periods, though even a week can be a problem. i have had the float valve corrode on an FCR to the point that the float will not move, which then necessitates teardown and getting a new float valve, which is about $25 at my local parts store, if you can find one in stock. the seat, being brass, seems to hold up fine. the oring around it less so.
running the bowls out of gas is a very smart move, which i can't do till i get rid of the vacuum petcock but that's another subject.
the booze also swells and dissolves typical carb rebuild o-rings (nitrile, buna-n etc) which can cause innumerable problems. viton only if it's touching fuel.
Fortunately, we have all octane ratings available without ethanol and ethanol fuel is marked seperately at the bowser. So we have consumer choice re octane and ethanol Vs non ethanol fuels, with any combination thereof depending on the range available at the gas station.
So ethanol can be avoided and isnt synonomous with higher octane fuels down here.
I feel our high octane fuel might not be harmful like some in the US, more a pita. With E fuels I've seen everything in carb float bowls from a blue green gel to what looked like burnt sugar.