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Small vent + advice (mostly re carbys)

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by Peppy, Oct 21, 2012.

  1. Hey all,

    The bike is an old Honda CBR250R which I've owned for about 3 months. When I first had it it would occasionally only fire on three cylinders while riding. If at idle, the bike stalled, otherwise it would disappear after ~30-40 seconds of riding (or after revving the bike). If the bike was idling and this happened, she'd stall unless I revved the bike. Eventually this happened and she wouldn't start, so ended up taking her to a mechanic.

    got new plugs, carby cleaned, fuel tank (and pump) flushed and coolant topup for good measure. Also asked for a general check of how things were - all was reported to be well.

    The first ride on her after this, she was running very hot - got her home and needed to add ~ 1L of distilled water at the radiator cap. This ride was ~300km with no issues re: cylinders firing. It was running hot, presumably because I needed to add a liter of fluid to the radiator at the fill cap (once i got home and had a look at things.)
    Coolant levels seem to be okay after a number of short rides. As far as leaks go, I can only find a tiny little dribble out of where a hose connects - hardly responsible for such a large fluid loss.

    I wanted to throw in a fresh oil filter and new oil given how many kms I'd put on the bike, so I degreased the engine and gave her a good clean. All was well, but I've noticed oil leaking from the valve cover, and potentially elsewhere (it'll be difficult to know for sure unless I fix up the valve cover leak first).

    Because I was taking the tank off to check on the coolant levels, a brittle fuel hose that connects to the tank has broken (3 times, because I cut and rejoined it) I have since replaced this hose. I've also noticed that the cable that returns the throttle body is not tight.

    Now the 3-cylinder stuff is happening again, and at higher frequency than before. In my most recent test ride I got 13 kms down the road before it happened, then it was recurring every 2-3 kms.

    I'm frustrated because I took this thing to a mechanic to get the coolant level topped off, which appears to have been done poorly, The carbys cleaned which appear to be having issues again so soon, and to have a general check over, in which oil leaks and a slack cable weren't reported on. on top of this, I've found the 4L of oil I bought from this mechanic somwehere else but 20 bucks cheaper. To top things off the weather is getting really good lately, but I don't trust the bike further than i can push it!

    On to the advice portion:

    Re: Carbys.
    Disassemble and clean myself? Is there a soft option that I could do to clean them without disassembling?

    If the carbies were cleaned properly, Are there other factors that could cause them to get blocked again?

    Are there any potential causes that are independent of the carbs? ie: non fuel-delivery related.

    Should I consider getting rid of the bike in exchange for something a little newer?

    All advice appreciated!
  2. Yes. Remove the airbox and spray some aerosol carb cleaner down the throats (with the throttle open).

    Most likely cause (assuming it is a blocked carb) would be rust in the fuel tank. Always worth fitting a small inline filter on the hose between the tank and the carbs (the filter inside the tank has more than likely perished long ago).

    If it's always the same cylinder then a problem with the spark plug, plug lead or even possibly the CDI unit could be the cause. Easy enough to tell which cylinder isn't firing, just (very carefully) check the temperatures of the 4 exhaust pipes and see which one is colder.

    If you're paying a mechanic for everything then yes, quite likely going to be cheaper in the long run to spend more on something newer, or at the very least easy to fix (ie a 2-cyclinder, 2-valve GS500 is a lot easier to troubleshoot than a CBR250 - and a lot cheaper to buy parts for).