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What type of petrol to use?

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by ametha elf, Mar 30, 2010.

  1. Last Sunday when we were out riding, I wasnt expecting problems on a newly purchased low mileage bike, but a few kilometres along the road, she started coughing and spluttering so badly I thought she was going to stop. Hubby put her into neutral and revved her hard for a few minutes, then later he put some Injector Cleaning fluid into the tank. She gradually began to run better from then on. Today I was speaking to the dealer where I bought her from, who told me that I should definately be using normal Unleaded (91) and not Premium Unleaded (95) (as I always have done). He said using the Premium 95 would totally ruin the engine. Also said he had the carburettor cleaned out just before I took delivery. I'm wondering if either the Premium Unleaded petrol or having the carburettor cleaned would have caused the coughing and spluttering? also would using Premium Unleaded been the cause of the Main Bearing collapsing on my old bike?. I've always used the 95 petrol thinking that was a better option than the standard Unleaded 91, now I'm not so sure.

  2. If the bike is designed to run on 91 use it and save your money.

    Some people have said there bikes have performed worse on the higher octane fuel. (from memory I think those fuels are denser and may not vapourise as easily which may affect some some bikes??? I am sure someone will correct me if I have this wrong),. However I doubt that this effect would be so bad as to cause coughing and spluttering. I certainly doubt it would cause bearing failure.

    Carbs may have been cleaned out but how is the tank? I gave mine a clean the other weekend and couldn't believe how much cr@p came out of it.

    Do you run fuel-line filters or just rely on the screens which are in your tank. If the latter I would invest in some fuel filters (probably less than $10). Even if that isn't your present problem it's probably a good investment.

    Could also be some sort of sparking problem, although given the intermittent nature I would lean towards fuel issues.

    However I am gonna watch replies with interest cos my bike is also intemittently running rough.
  3. I was told by my Yamaha service center to run 91. Higher octane fouled the plugs apparently.
  4. From what I've learnt in tafe so far.. higher octane fuel than its designed to run on will cause no damage what so ever

    You may lose up to 1% horsepower depending on the machine which not even an experienced rider will notice, and never heard about fouling plugs because of it..

    Its also a good preventative measure as higher octane is safer, since it prevents detonation (more important when you build/modify your engines at home)

    It could have just been a bad batch of fuel and a chunk of crap got caught in your carby jet (with the cleaner dissolving it and freeing up the blockage)
    Quite likely if you visited a servo you don't usually go to.

    Adding an extra in line filter probably won't help (just in this case GreyBM, EFI bikes would definitely benefit)
    As its a gravity feed system, putting in any kind of filter is too restrictive and it doesnt flow enough to get fuel into the engine faster than its being used. (Dad tried this same thing and discovered the limited flow issue, and he always runs premium too)

    It would be wise to double check all the filters that the bike DOES have (usually at least 2 between the pickup and the carbies).
    Also because someone SAID the carbies were cleaned out doesn't mean he was telling the truth. Its a fairly simple (but very time consuming) procedure, but worth it if you suspect they are dirty.

    Let us know if you make any progress
  5. Stupid statements like this don't help. Running 95 when you only need to run 91 shouldn't cause any major problems it's just potentially a waste of money

    It's most likely you got a crook batch of fuel or water in the fuel.

    Did it still have the fuel from the dealer in it? what type of 95? Ethanol?
  6. When I bought the bike, it only had enough fuel to go about 20 klms, so possibly it was the old petrol still sitting there for the 8 months or so it took to be sold. Going riding again this weekend so am curious to see how it goes this time. Thanks for your advice guys.
  7. I'd be voting for the "dirty batch of fuel" scenario. That sounds a lot like what happens if you pick up the water from the bottom of the tank at the servo. And the addition of the injector cleaner adds weight to this probability. Many of these products contain hygroscopic agents that absorb water (the old-school cure for water in the fuel, BTW, is to pour in half a litre of metho; it does exactly the same thing)

    As for PULP. If the bike's manual says use Regular Unleaded, then use it. I can't imagine that your bike would even NEED PULP, as it's generally needed by high-compression engines rather than cruisers. Having said that, I use regular nearly all the time, but, every now and then, I'll put a tank of PULP in and it seems to help (something to do with cleaning out the combustion chamber or something like that)
  8. So you might have sucked a bit of crap into the carbies when running it early on.

    Should be fine now.
  9. Yep, that also adds weight to the "water in the carbies" theory. A tank that has very little fuel in it that is then left for a while, will collect water in the form of condensation. As petrol is lighter than water, the water collects in the bottom of the tank and is first to be sucked into the carbies when the bike is started. This is especially more likely in a humid climate like that which is the norm in Brisbane.

    If you are going to store a bike for a while, they say that the best advice is to either fill it right up to the very top, or drain it so that it is completely empty.
  10. I've noticed that all the petrol stations I've been to in sydney and outer suburbs only have 91ethanol mix, 95PULP and 98PULP. I used to just run 91ULP but now unless I'm happy to run ethanol I have to run 95PULP.

    Are there any companies that have ordinary 91 in greater sydney area or has it been phased out?
  11. Yeah it ever varies from station to station and doesn't go by company. I think Caltex/Woolworths still run 91ULP at a lot of places.
  12. It should be noted, although I'm sure that it has been before, that NONE of the major distributors of motorcycles in Australia recommend the use of ethanol-blend petrol in motorcycles that have carburettors.
  13. Just to be a little bit clearer, the metho does the hygroscopic thing, not the injector cleaning thing. :)

    I always thought half to full cup of metho was the required amount in a tank of fuel???

    Cypher, it's true a higher octane fuel wont cause damage directly, but it can foul plugs if the mixture now becomes too rich. Also if the higher octane rating is obtained from ethanol blend, it MIGHT cause elastomers to perish. You can expect a loss of fuel economy with an ethanol octane boosted fuel if your engine isn't designed for the higher octane.

    Its also a good preventative measure as higher octane is safer, since it prevents detonation (more important when you build/modify your engines at home)
    Preventative?? Safer?? What the?? Drop some on the ground and drop a match on it. Is it safer?? If an engine running 91 doesn't experience pinging, why would that engine be safer with 95?

    It could have just been a bad batch of fuel and a chunk of crap got caught in your carby jet (with the cleaner dissolving it and freeing up the blockage)
    Highly likely.

    Adding an extra in line filter probably won't help
    It wont? For the vast majority of cases, filters will allow a flow GREATER than the engine use - especially on a small engine, and this should keep crap out of the jets for 10's of thousands of kms.

    +1 on picking up some crap from the fuel, very likely if the bike's tank is old, if the servo's tank level was low or was recently replenished which stirs up muck.
  14. With regards to the ethanol, if you look at V8 supercars (just as an example).. They are using the same engines, tuned to the same horsepower with E85 (85% ethanol blend) that they used to run with a high octane regular style of fuel.
    Since the changeover they are burning 20-30% more fuel by volume to get the same horsepower.
    So yeah, definitely worse economy for something not designed to run on it.

    And using E10 in something 15+ years old may destroy some fuel system components as you said, like some rubber lines, or corroding metals. It should still be ok to use as a last resort in old vehicles as long as you use it ALL and switch back to regular stuff before sitting it in the shed for a week.

    What I meant by this is if you have an engine you build yourself, or modify.. so it no longer has a factory recommended octane rating. If you raise the compression or advance timing it can start pinging, higher octane usually helps (as well as detuning).
    But yes you are right, if its designed for 91, thats all it ever needs..

    And this was aimed specifically at paper type filters, I forgot to mention that part, sorry. Dad has a Virago 750, very similar to the bike in question here and found that adding an extra paper filter restricted flow so much it barely ran. Mainly because there was no pump to force it through, and gravity wasn't enough when the tank was less than 60% full.
    Keeping the factory filters clean and free from tears was all it really needed.

    With a mesh filter it would have been fine, but the bike already had 2 of them, maybe even 3.. can't remember.

    So for the most part we were both saying similar things, maybe I just wasn't explaining it properly 8-[

  15. My experience (with gravity feed and carbied bike) is that my bike has screens in the tank that do little except keep cattle and large dogs from being sucked into the carbs. This led to regular issues by crud that happily passed through the filter and stopping the needle jet on the carby bowl jamming open and overflowing all over my boots. While a simple road side stop remedied it (until the next piece of crud past through) it was tiring and so I fuel filters in the fuel lines. I have had no apparent problems with restricted flow and my boots stay a lot drier and are probably safer to warm by the fire.

    As Rob says, gunk in the carbs is going to restrict things lots more than a filter which has been designed to pass fuel. However all bikes are different and I bow to your dad's experience.
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  17. Problem solved. She ran rough again thismorning, - I rode her til almost out of petrol, then filled the tank with Unleaded 91. She ran like a dream. I had no idea a different type of petrol would make so much difference. Have learnt something today!