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ZZR 250 stalls on take-off when cold

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by jack_1313, Jun 4, 2013.

  1. In a few hours, a mate will be bringing his ZZR 250 around so that I can find and hopefully resolve the problem he has been experiencing.

    The bike in a 1994 ZZR-250 which claims to have done about 50k kilometres, although it’s possible that it’s been around the clock. A few months ago, his mechanic replaced the cylinder head and conducted a full service. Thus, all the basic trouble points – carbs, valve clearances etc – should be ok, but the details of the service I do not know much about. I put a new battery in it myself a few weeks ago.



    When cold, the bike will start and idle fine (using the choke to begin with). However, when trying to take off, the engine stalls as the clutch is engaged. I had a shot on it the other day: it didn’t matter how hard I revved it, there was just no pulling power whatsoever.

    However, my friend has been able to get moving by rolling the bike until he has enough speed to click up into second gear. At that point, the bike becomes responsive. Once it has warmed up a bit, he is able to stop and take off as normal.

    Given these symptoms, I’m thinking about a weakness in the ignition system. I already plan to replace the spark plugs. As the bike fails when cold, I don’t think the problem is the ignition coils – coils tend to fail when hot. But the ignition system is where I plan to start.

    For now, I’m just looking for some more ideas about what could cause this that might help guide my approach. Thanks!
     
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  2. My ZZR used to do the same thing if I tried to drive with the choke on, even in the cold. I replaced the sparks first so maybe that did help. But what I did on warm up was use the choke to turn it on, then let it idle at 2000rpm for about 30 seconds while I put my helmet on, then turned the choke off. The revs will drop lower than normal but that's ok. Then the gloves go on and I'll ride off. After a couple of minutes she'd be riding fine in the 5deg weather.

    As I understand it the choke works by putting extra fuel in to the mix to get it to start. If you turn the throttle with the choke on you're flooding the engine. Guaranteed to make it stop. At least that's how mine worked. I'm happy to be corrected on any point.
     
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  3. The fact that second gear is fine and it doesn't sound like a slipping clutch might indicate that 1st gear is badly worn and not engaging.
     
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  4. If the bike is moving at all, the gear is engaged.

    reads like a carbie problem. I'd be looking at the idle mixture screw and the idle settings.

    Also, in cold weather, it's alright to for a few minutes with the choke on. Making the idle mixture slightly richer will help get the choke off sooner.
     
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  5. Hey guys, thanks for your suggestions.

    Firstly, my mate had to bail due to being overloaded with work. The bike is now "booked in" for the 16th, although I might drop past his place and whack some new plugs in tonight and make sure his battery terminals aren't loose.

    Unfortunately, it's not a issue of not being familiar with the need to use the choke. He's had the bike for about two years and rides it every day, so he's well accustomed to the start-up procedure. Apparently, he wasn't able to get the bike to take off after trying for 20 minutes the other day, which is when he got another friend to push him and had success with a "rolling take-off".

    With regards to second gear - when I rode it, I wasn't able to test taking off in second because I couldn't get it to bump up, even with a bit of a roll. Apparently his bike will only go into second when there is some speed happening. So we could be looking at a gear problem, but if that's the case, I have no idea how we could explain why it functions fine once the bike has warmed up to normal operating temperature.

    Re: carb problem. With the bike giving zero pull, but idling and revving freely in neutral and running fine once warm, it would be an unusual carb issue. Once it's in my garage we'll open the carbs and have a good look around to make sure everything is in order.

    Thanks for the suggestions! We'll see how it develops.
     
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  6. Yeah the ZZR has a positive neutral finder. When you're at lights you can go to neutral with no issues at all. Unless you're above 5kph second will not engage. Kicking up only goes into neutral. If you want to try starting it in second, put the bike on a rear stand and spin the rear wheel. While it's spinning kick the gear up.
     
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  7. Clutch is buggered.
     
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  8. Update:
    I put new plugs in last night and the problem remains unchanged, although the old, brittle fuel line must have split somewhere as I removed or replaced the tank because the bike now pisses out petrol.

    The bike still provides absolutely zero pulling power as I try to take off.

    My pal revised the details of the problem with me. In fact, the bike does not function fine when warm. Rather, it just functions better.

    Thanks Blabbs. Could you elaborate more on that?

    The bike is hard to push around when in gear even though the clutch cable adjustment looks fine. So it looks like the clutch is either not fully disengaging for some reason or the plates stick a bit when the bike has been sitting in cold weather, which could be normal. This doesn't seem to affect the idle of the bike when sitting in gear with the clutch lever pulled in.

    It looks like the bike is low on oil as I couldn't find any in the sight window, even when I tipped the bike a bit.

    If the clutch was wrecked, wouldn't it either slip or want to lurch forward when I go from neutral down into first?

    Cheers!
     
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  9. Blocked main jets can cause this problem. They will start & run fine in neutral & rev, but once under load with throttle opened up they will die. Water in fuel pehapps.
     
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    • Agree Agree x 1
  10. what is coming out of the exhaust at idle and under load (before it stalls) and what colour is it

    put a white piece of paper in the path of the exhaust and see what appears on it.
    you should be able to tell from the result(s) whether the mixture is too high (suggesting something to do with the carbies or air intake)
     
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