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1988 EX250 troubles

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by yeremiah, Oct 2, 2015.

  1. Hey how are you all. Once again there is more problems with my 1988 ex250.
    Firstly there is a nice knocking sound, clutch basket? Main bearing? Other things heres a link of someone eles bike with same problem. Mine sounds similar, but when i pull the clutch in noise get less. Other posible causes?
    Had a valve adjustment to 0.006 inch

    Then i have a random power lose between 50 and 80 km/h. For example it gets really bad at 80. I will hold the throttle at 80 then it starts to power jerk like fuel starvation and inevitably when it's really bad i have to hold the throttle 1/4 to1/2 way in 6th gear just to accelerate. This however doesn't hold at 80 but rather accelerate past 80 and i have to give doing this just to maintain 80. At 60 same power jerking but i can hold throttle 1/4 way and it will hold. This is more throttle then i usually use. I'm struggling and going slightly crazy.

    Now, i have taken apart the carby and cleaned it well. All jets and what not. Idel mix screws are 1.8 turns out. No vac leak. All that is good. Before people ask the fuel tap is vac operated so fuel is pulled through while engine running. Not if i turn the tap on and take the fuel line off.. air filter is fine. Been running on 98 past couple of week. Open could the carby jets be partially blocked again? Going to clean the fuel tank out and get tap seals anyways. And carby again. Just asking anything i should go over? Things it may be need new jets?

    I'm also servicing the bike again this weekend and would like to know things i should look for. Taking clutch apart and stator. Thank you.

    Also i think it may need a carby sync.
  2. Knocking noise is probably the same as what they (gpx250, zzr250) all do. If the idle speed is too low it sounds really bad, but when you pull the clutch in, it mostly stops.
    Synchronise the carbs. Replace spark plugs. Try lower octane fuel. They do happily run on 91 RON unleaded (owners manual does say this). When you clean the tank, refill it with 91 RON and go for a ride. It might help.