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Info On Old Engine

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by Tnate, Oct 10, 2005.

  1. Hi all,

    I recently acquired an old 1984 Honda CM 250 Custom, which is pretty much the old CB 250, except it is belt driven. Seems to have the same engine and general setup as the CB250, but has subtle differences like the seat, fairing etc.

    My simple question is, does it run on Leaded or unleaded. I've been running it on Optimax, but I would like to know if valve addidtive needs to be used to stop recession. The last thing I want to do is fork out for a top end rebuild, but I also don't want to add lead if I dont need to.

    Also, does anyone know where I can get my hands, or eyes on a user manual?


  2. first of all the most likely thing you will be told is dont use optimax. It is not good for your engine. I would try using bp ultimate or mobil 2000. And yes if your bike originally ran on leaded fuel use an additive which is designed to be used with the pulp.
  3. In 1984 it would've undoubtedly ran on leaded, but (not necesarity) it may have harder valve seats allowing it to run on unleaded. I would be running on 95 PULP with some flashlube.
  4. Japan was actually one of the earliest countries to phase out lead from petrol and started as early as 1970 due to lead contamination detected in traffic police. Apparantly only around 1-2% of all petrol sold in Japan by the early '80s contained lead so chances are your bike probably does have hardened valves and won't need an additive, will still need to be run on 95+ octane fuel though (unless retuned).
    Edit: This is assuming of course that CM250s sold here were the same as bikes sold in the Japanese market (can't see a reason why they wouldn't have been though).
  5. My second wife had a black and chrome CM250 Custom, it was the only bike available at the time that she could get both feet on the ground with, as it had a very low seat height and she was just under 5'4" tall. It was a neat little machine, but the chrome was of poor quality and really needed to be looked after. It definitely ran on leaded fuel, and not much of it at that. Hers had been converted to chain drive by a previous owner, possibly because the belt drive parts were hard to find in Oz, but I am guessing. There can't be too many in Australia, an interesting little rarity I think.
  6. My bike is an '84 model Jap bike, and the manual clearly states Unleaded Petrol Only. I would guess the same with yours :)