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The Saga that is my MC19

Discussion in 'Technical and Troubleshooting Torque' started by NrKy, Dec 31, 2009.

  1. G'day!

    My MC19 is like a precocious child, it has been nothing but a headache since I bought the thing, so I figured I'd make a thread about it, and see if anybody has any ideas as to how I can get this puppy working properly again.

    My beastie is a 1989 Honda CBR MC19.
    She worked fine when I bought the bike.

    About a year after I bought her, I started getting random losses of power, and the bike wouldn't turn over (starter motor works fine).
    After several hundred dollars worth of towing fees over a year, and a couple of 'services', a new battery, I was told by the mechanic that it might cost at least $400 for them to have a look at it, and that's if they only need to clean the carbies out.

    After a while I noticed that when she loses power, it's when the day is hot, or I've been riding it hard for an extended period of time (ie. tuesday learner rides), even if the thermostat is only 3/4 of the way up. (In fact, it never shuts down when the thermostat is at 100% heat, which I find wierd)
    She doesn't lose power WHILST I'm riding it hard, she only does it AFTERWARDS, like if we are going on the freeways, or riding it back home past the MCG.

    One time it wanted to run out of power, instead of doing what I normally do, which was to drop gear and slow it down a bit, I decided to do the OPPOSITE of what I normally do... I went up a gear, and opened the throttle all the way. It sounded like it was trying to vomit, then gave me a MASSIVE boost of power, bringing me up to the maximum speed it could do, almost throwing me off of the bike. I only wish it was able to do that at the lights when I try to take off quickly. :(

    Another thing, she lags between when I open the throttle and when I actually get some power out of her... I get completely decimated by fast riders at the lights these days, no matter how well I ride her.

    I've been using 92 RON petrol in her since day1, which is what the mechanics and dealer have recommended. About six months ago I chucked some 'fuel line cleaner' into the empty tank (it had completely died at this stage), tried turning her over, nothing. I filled up the tank, and gave it another shot. She worked perfectly fine, and had a little bit of grey smoke coming out the exhaust (which she never does).

    I've heard that the MC19's have a 'gravity fed' fuel system, and that if you bypass the fuel pump, you get minimal power, but at least it will run. How do I check if my fuel line is blocked? I can't afford half a thousand bucks at the mechanics for 'labour' (aka. trial and error for three hours).

    Another interesting thing to note, is that one day when I ran out of power (on a 30+ degree day), some random JC-Decaux employee at the bus stop opened my fuel tank, did some lil funky trick to get the key out, left the tank open, and it started straight away. WHAT THE HELL?!? I used this trick once to get me home when I lost all power after a netrider ride, so I'm completely baffled as to what opening the fuel tank does to fix it.

    If anybody has any clue as to what's wrong with my bike, based on this description, please let me know, it's driving me completely mad, Geoff Taylor motorcycles have no clue what I'm talking about over the phone, and I can't afford to fork out half a thousand bucks for them to spend time trying to figure out what's wrong with it, when they might not actually fix it.

    Cheers, NrKy.

  2. This part sounds like your fuel tank isn't "breathing"

    When your fuel tank is full it only has petrol in it right? (plus a tiny bit of air, unless you can get it really full).

    When you run your bike and use the fuel, the tank must fill with air (atmospheric pressure) otherwise a vacuum will form. This vacuum will stop the fuel from being available to the carbies/ fuel pump.

    By the guy opening the fuel tank he has released the vacuum...Allowing the fuel to flow......Basically the same principle when you shot gun a can of beer :beer:

    Check to see what sort of fuel tank breather you have...Make sure its clear and not blocked. Does it play up more when the tank is full or empty ? If it is a breather prob I reckon that it would play up more on a full tank.. The less air in the tank the quicker a vacuum will form.

    I have a ride on lawn mower which I lost the rubber cap liner (makes fuel tank breath.....)now if I use the mower with the cap done up tight it will stop working between 5 and 10 mins later....So I just crack the lid open a bit before use.

  3. Fuel tank breather tube blocked, you say? Hmmmm.... I will have a look and see if I can figure out which tube is the breather.

    That would be a logical reason why I'm not getting enough fuel pumping through after a two/three-hour ride without having opened the fuel tank. It should also explain why I am getting minimal power at take-off too.

    I'll get back to you on this one. :)

    Cheers, NrKy.

    P.S Does anybody know where I can get a copy of the workshop manual for an MC19? They're impossible to find. I need to figure out which hole in the top of the fuel tank is the breather/overflow pipe. Or even a diagram would be useful.

    P.P.S I spent another couple of hours staring endlessly at my bike to figure out where the breather pipe goes to... no luck, so I checked some more forums, found someone in the perthstreetbikes forum with a similar problem: http://www.perthstreetbikes.com/forum/f37/cbr-problems-87329/2 , 'bren's bike seems to have the same sort of symptoms as mine. It'll lose it's balls and give me a deep groaning sound before dying in the butt. As in, the same deep groaning sound you get when you roll-start a bike. ie. the bike died in the butt but kept ticking over due to the fact that I was still rolling with momentum.
  4. Okay, I found a manual!
    So for the 'breather tube', is that the 'carburettor breather tube', or the 'tank cap hole', or the 'vacuum tube', or the 'air vent'.
    Wheeeeeeeee, I wish I had've taken mechanics classes in TAFE instead of info tech, LOL!
  5. Try taking your tank cap off (unbolt entire assembly). Clean everything you can within that assembly as most bikes have the breather built into the cap very close to the overflow.

    I would probably use something like carby cleaner to clean it out, you dont want something in your fuel once your done that could harm the bikes fuel system.
    Others hear will have a better suggestion on what to clean it with i imagine.

    While your in diagnostic mode with your bike, google how to test your reg/rec and check that as well. It doesnt sound like its boned, but will cause similar problems to what your describing. May as well check it while the bikes apart.

    Would also be worth draining your tank off the bike and making sure its fuel and only fuel that comes out. Then while your at it, take the petcock (thing the fuel lines come out of thats screwed into the bottom of the tank) off and check to make sure your filters are not covered in crap.
    Again this doesnt sound like the cause of your issue, but while your at it.......

    All these things can be done with minimal tools and little mechanical knowledge.
    Just be careful when messing with fuel. Dont be smoking while your working etc.
  6. reg/rec problems are associated with a flat battery, as far as we know this is not happening.

    Check battery if it reads over 13v with engine off and 14v with engine on, no problems with reg/rec and battery.

    But I would start with cleaning fuel tank breather too. Who knows when it was last done.
  7. Just took off the fuel cap, gave it a clean-out, and there was a lil bit of dirty grease in the breather hole on the cap. At least, I assume it's the breather hole, as it creates a vacuum-seal with a connecting hole on the body of the tank when the cap is in place, on the right hand side. There's also another hole, but it's on the left-hand side of the cap, and looks to be where the overflow of petrol would go if you spilled some whilst filling the tank (bike leaning on side stand = overflow goes to the left = put overflow drain hole on left side).

    I did some standstill revving, and it's still having the same slow-response problems as before, but I'm yet to take it out on a ride to test if she'll stall on me halfway through princes hwy.
    One thing I did notice, however, was that if I bring the revs up, pull choke to full, close the throttle, put choke off, let the revs drop to where it almost stalls, then open throttle to full, it responds REALLY well, as in it doesn't slow down when it hits 3,000 rpm. I don't know why my bike does that, it's annoying... if I try to take off at the lights, I get no to little response whilst changing gears, and the power only picks up after 4,000 rpm. hmmmmmmmmmmmm

    Back to the drawing board I guess. ](*,)

    Does anybody know how to clean out the breather tube from the tank? Where does it lead to? Is it safe to pour de-greaser down there and pray that it'll clean all the shite out?
  8. How long since youve looked at your air filter?
    Might be time to replace it.