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Older bikes - leaded substitutes VS high octane unleaded?

Discussion in 'Technical and Troubleshooting Torque' started by ceebee, Sep 20, 2007.

  1. Gday
    I have a 1979 Honda CB650. Have heard many opinions on the best fuel to use for older bikes designed to run on leaded fuel. Some mechanics have told me that the small bottles of lead additive you get over the counter at servos are ok. Some have said they are bad for engines as they cause build up of carbon residue on the pistons. And some other mechanics have told me i should only use high octane unleaded. I am thoroughly confused. :? Is there anyone else on this forum who rides older bikes, and what fuel/additive have they been using? Any advice regarding tuning, etc with high octane unleaded? Thanks guys.

  2. Hi Ceebee, I beat you by one year ('78 Ducati). The old girl runs just fine on premium unleaded or the next one down at some servo's but you need to add "Flashlube" or equivalent to each tank as these older babies were designed around lead being present to cushion the vaves on the seats and supposedly lubricate other bits in the upper cylinder area. I've had the Ducati for 22 years now and once leaded run out she's been fine on the new fangled funny fuel, no extra carbon build up or anything.
    PS it does "ping" horribly with standard unleaded.
  3. Japan banned lead from standard fuel as early as 1975 - so unless your bike needs high octane fuel (which still contained lead in Japan though at much lower levels than anywhere else) then it should run fine without any lead additive since it would've been designed not to need it. European made bikes are a different matter.
  4. To clarify, lead in petrol is too lubricate parts and cushion the valve seat (especially). The octane raising is a nice side effect.

    To switch an engine off leaded petrol you need to get some hardened valve seats.

    Having said that, I also believe that Japan went to lead free a long time before anybody else, so it may well be you can just get away with just high octane fuel.

    To be sure find out what the speced fuel was in Japan and you should be fine. It's unliky they made a different bike for OZ.
  5. Thanks fellas. That really helps. Wonder if there is any harm in actually adding the lead additive "just to be safe"?
  6. Okay I know this isn't a bike, but my car (1974 VW beetle) needs to run on high octane petrol, since leaded went out. I've had the engine rebuilt to take unleaded, but it still needs the high octane anyway (runs like crap if I use normal unleaded TBH). My mechanics & other beetle drivers recommend that I use the 'flashlube' type additive once every other fillup, but I don't use it at all. However I do pay for not using it each time my car gets serviced as bits & pieces need a little extra work. I imagine that my little car would run cleaner & smoother if I did use the additive.
  7. Nup, only real problem was that lead destroys catalytic converters (which is why it's actually illegal to put in an unleaded car). Could be a slight risk of fouling if you use too much perhaps - lead does tend to build up in engines. Leaded fuel actually contained another chemical to wash the lead out, otherwise you would have only needed to use leaded fuel once a year or so (and the fuel companies made most of their money on selling the lead).
  8. The additives are nasty stuff to handle too. I forget the stuff I used to use on the Laverda, but even just opening the cap used to make me nervous.
  9. They used to use ethylene dibromide to flush the lead, like a lot of organic chemicals it's one of those ones that no-one could prove was bad for people - but it's certainly not good for you either. It's suspected of causing brain damage, and there's cases of infertility in males as a result of breathing the vapours.
    There's an excellent article on lead in fuel to be found here if anyone's interested:
  10. Let's not start on the known carcinogens in unleaded fuel, or the large study done in Canada after it was introduced showing an increase in certain types of cancers........
    Anyway, as said above any bike after the early to mid seventies built in Japan was built for unleaded fuel, so just use whatever octane rating you need in unleaded.
    There is evidence that normal cast iron seats or cast iron heads become hardened in use anyway, due to regular heating and cooling cycles, plus the constant hammering of the valves on teh seats.

    Regards, Andrew.