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Fuel and revs

Discussion in 'Technical and Troubleshooting Torque' started by JamesJoyce, Nov 10, 2004.

  1. Hi, just got my 2004 Honda CB250 back from its first service. Seems no different from before, so I guess it was prepared properly to start with. The service guy gave me a couple of pointers though, that I thought I would let the group know about.

    I have been having a little bit of trouble with the plugs fouling because I am only 3km from work and most trips I do are under 5km. I have been finding that by the end of a working week the bike breaks down (misfires) badly at >5000rpm with more than half throttle. I normally use less than half trottle and the bike rarely sees over 6000rpm .. otherwise I end up breaking the speed limit. A brief run at 80 km/hr out to the harbour on the weekend cures this for a few days.

    The first suggestion was to steer well clear of Shell standard unleaded fuel and change to Caltex premium fuel. The service guy swears by it for his car and recommends it to anyone he can.

    The second suggestion was to forget using 5th gear around town .. keep it for the highway. He even suggested that 4th gear was probably a no-no for short trips at less than 60 km/hr (40 mph), especially until the bike is fully run in. Seems like my tiny fuel bill would go up by at least 50 cents a week with all the extra revs !

    Any comments on those suggestions ?

  2. Howdy James, welcome to the forums. I've got a CB250, and while I don't have the problems you have I do find that I need to run it on the choke for about 4 - 5 k's when its cold ( not sure about you). I reckon if I never got it off the choke it'd foul plugs pretty bad too. You might need to warm it up a bit longer so you can run choke free. Hope this helps.

  3. Howdy James! I had similar probs with Bond until I changed to Caltex fuel. My trip to work is longer but mostly freeway (read carpark at that time of day!) & yeah I often do the whole trip in 4th or lower with no adverse effects so far!
  4. Yep I use the choke (as little as possible) for the first kilometre. Don't warm it up much before I head off (maybe 10 seconds). It didn't seem to help to warm it up for a minute (ie. it was still a fussy biatch), so I just give it 10 seconds ride off with just enough choke to stop it stalling at idle. Then I just baby it a bit for the first km until the choke is off.

    I wanted to install hotter spark plugs but the Honda dealer really wasn't keen. I reckon I probably will consider that again once I start using premium fuel.
  5. I agree that you should use premium fuel, Caltex or BP. Stay away from optimax if you can, and dont be afraid to give the bike some revs when taking off from lights or whatever. As long as you keep it out of the red zone and the bike is warm you wont do any damage by using the whole rev range. And you have first hand experianced what taking it easy on an engine all the time can do. I wouldnt go for the hotter plugs if they arnt a listed option for your bike, you can do more damage than good. Cheers, good luck.
  6. surely there would be a range of plugs that you could use?

    I was always taught not to overuse the choke and even to warm a bike up with the throttle as preference. I'm not sure why but I thought that it had something to do with fouling plugs as you've experienced.

    Also whats the drama with optimax? Its stated in here often that its crap. I've used it heaps in my bike and use regular unleaded (shell normally) in my car and have had no problems - or is it just that I don't know what I'm missing out on?


  7. Ive never had a problem with fuel, but Ive never run optimax. I have seen and heard of some bikes needing fuel pumps and injectors cleaned because optimax is to dense for the small components of a motorcycle, Yamaha and Suzuki both say to stay away from Optimax as do tuners of 2-stroke engines. I just figure its better to be safe than sorry.
  8. Plugs

    Honda describe three plugs for the CB250. One for extended running in hot conditions, the standard one, and one for operation at <5 deg C. It is this last one, the hotest that I was considering, but I guess I would also consider a fancy after market plug if someone could recommend one that wasn't a gimick.

    Apart from pre-ignition/knocking (which I imagine I would hear and thus decide to change my plugs back), I would have thought the only other issue with a plug running too hot is that the life of the plug would be reduced.

    Aparently the CB250's are noted "cold engines", which I believe translates as being pigs when they are cold. If only I could retrofit fuel injection then I wouldn't have to worry about things like chokes and cold running so much.
  9. I have mates who ride Suzukis, GSXR1000 and 750, Hondas, CBR1000, CBR1100, CBR600, Yamahas, R1, YZF750 (pre-R7 model), BMWs, R1150RT, K1100, K100 and a smattering of other bikes, both carb'ed and EFI. On rides, we've all filled up at Shell on Optimax. I know that at least 4 of the above have Shell fuel cards (work discount) and have never had any problems.

    I'm of the view that the Optimax thing is little more than an urban myth. Where people may get into problems, is if the servo has had a bad batch of fuel, and even then, how often does this occur? I've never had it in near 30 years of riding and driving.
  10. I'm sure someone else has posted this link elsewhere in the forums, but all the same, I'll post it here again:


    Basically, Shell reckons some bikes might need adjustments before they will run correctly with Optimax.

  11. G'day James welcome!!!

    If you've had you first service then in might be a bit late but have a read of this thread. Its about how to properly run in your engine but generally the run in process is 'complete' after the first service.

    I'd say in lower gears and let the engine rev that should help keep the bike subtle during the week, and use a premium unleaded fuel.
    BP Ultimate and Mobil Synergy 8000 (unfortunately Mobil's website doesn't allow direct links so this link will end up at the main page) are my choices in that order, but you probably don't need to get a 98 RON fuel, so stick with the 95 RON Premiums, BP Premium Unleaded, Caltex Vortex and Mobil Synergy 2000, etc. But as others have said there are issues with Shell Optimax but I'm not sure if the Shell Premium Unleaded is similarly effected. My guess is it isn't but I'm not taking the chance with my baby.
  12. Just rang Mick Hone Suzuki to talk about the issue the response from mechanic (didnt' get his name in service was0

    "Its not just suzukis that have a problem. The problem occurs more often when you are doing large numbers of small trips, if you are on the gas all the time or do lots of long trips or highway riding then it probably hasn't shown up. It is a densor fuel that also seems to 'go off' very quickly. It is worse in carburettor bikes than fuel injected and is also worse in small cylinder bikes. His advice of the fuel to run was standard unleaded - doesn't matter where purchased from, but on very hot days to run premium - ie over 40degrees. He felt the best premium was the Mobil fuel and also felt that the problems with optimax probably weren't confined to shell fuels'.

    Well I wont be using it anymore - I learnt something today.

  13. James, Have a read of this thread for a little more wisdom and perhaps some hearsay as well.
  14. Fuel

    Ok I have read of the running in info .. got that.

    As for the fuel info, apart for being wary (and maybe unecessarily so) of Optimax and the BP equivalnet ... I can't be quite sure if I should just stick with unleaded or try the Caltex of Mobil premium .. guess I'll just have to try it and see.

    Only hassle is that it takes me 6 weeks to use up my 15 litre tank. ... which might be a good reason to avoid premiums if they go off quicker.

  15. welcome to the forums.
  16. What about 7-eleven fuel?

  17. probably best off using sand or grit instead, you know, something something less damaging to your engine :LOL: :LOL:
  18. Hi guys,

    We had a similar topic on a Laverda site recently. A number of points surfaced:

    1. Standard unleaded was treated with suspician. Use premium. Lets face it our tanks are relatively small so it only costs 10s of cents more. Think about it in terms of how much a cup of coffe costs.

    2. Optimax was also treated with suspician. It also had its defenders. Make up your own mind. I use the BP premium.

    3. When starting use minimal choke. Personally I use it just to get the old girl to fire, then I use then throttle untill its warmed up. A bit of a hassle but I havn't fouled plugs since using this practice.

    4. Fuel goes off. Replace your fuel if it's been in the tank for a while. If you only do short trips only buy enough to get you through a week. 2 at the most.

    5. There was some theory about the viscosity of modern fuel being thicker for fuel injection. Take from that what you will.

    As for the question about 7-eleven fuel. It depends on where they are buying their fuel.

    A significant proportion of fuel is now being brought in from SE Asian refineries by PD - Van - Omeron. This fuel is made from sour crude. This has a higher level of Sulfur in it. When your nieghbours car smells like rotten egg gas you know they are buying Woolworths petrol. I WOULD NEVER USE IT IN ANY OF MY VEHICLES. Check out where your local supplier is getting their fuel. This applies for independants also.

    I hope this helps
  19. Fuel

    I gather that premium fuels go off faster than regular. Given that it takes me 6 weeks to get through a full 15 litre tank that is a problem. I have experienced some minor problems (at high revs and throttle) with the regular going off (I think), although I do top up my tank every 2-3 weeks. Perhaps I should sneak some octane booster in at each top up to counter the fuel ageing.

    To run around with a low fuel level all the time is not a good idea I think.. because the more air there is in a tank the more it will "breath", which will make the fuel go off faster and also encourage more moisture to accumulate.

    I have had trouble with the plugs fouling, but that has improved greatly by substituting more revs for choke. The extra revs definately help the engine warm up faster. I am only taking about being one gear lower than you might otherwise be, for short trips.

    I also use the reserve ocassionally, so that the fuel in that part of the tank is kept "fresh". I believe this is replenished whenever the tank is more than 1/4 full ... is my understanding correct ?
  20. James,

    Good point on the half filled tank. You are probable right. It probably doesn't help tank rusting problems either.

    I was also a bit harsh with the 1-2 weeks but my old bike is pretty sensative to poor fuel.

    An yes I also turn my reserve taps on, once my bike is fully warmed up, for a few ks, to clear out water and bad fuel.