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Thread: Quad problem

  1. #1

    Quad problem

    I cant get my Yamaha 250 Timberwolf to run smoothly (Should have bought a Honda, I know ).
    I have rebuilt the engine and replaced the jets in the carb but it will not idle when warm or run smoothly when not under load. It starts ok but does not like just bumbling along slowly on part throttle when out lamping. I'm guessing it is down to carb setting (Mikuni) but not sure what to alter. I was going to live with it but it was a right pain last night so does anyone have any ideas before I have another go at trying to sort it out?

  2. #2
    If you have an electric choke, unplug it and see how it does.. carb is prolly just shot... I have a chinese rebadged yamaha bear tracker and just got a cheap (50+/- euro) chinese carb. Also switched to autolite spark plugs.... I'll see what I can find as far as the parts I used and pm you in the next couple days. What year is yours?

  3. #3
    Hi mate do you have the correct heat range spark plug? And when the lump was rebuild bid you rest the valve clearances propperly not douting your work but somtimes you have to ask if the carb jetting is standard I would leave it alone unless the engine has been modified played these game for years on dynos. Tell us abit more about the quad what has it ha ld done to it or is it totaly standard?

  4. #4
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    Have you done a compression test? This will at least give you an idea of the state of your valves.
    Did you check your ring gap when you rebuilt the engine?
    Have you tried moving the needle up 1x notch?
    If you have had the engine re-bored you could now be running a little lean. Normal settings on the air bleed on the carb are about 1.5 turns out.
    Have you changed the air filter for a free flowing one? these do speed up air flow which rather oddly often means that the engine will then run lean.
    We need more detail on what you have done or did.
    “Man surprised me most about humanity. Because he sacrifices his health in order to make money.Then he sacrifices money to recuperate his health. And then he is so anxious about the future that he does not enjoy the present; the result being that he does not live in the present or the future; he lives as if he is never going to die, and then dies having never really lived.”........Dalai Lama

  5. #5
    Its a 1996 250 2wd I bought of that auction site "in need of a service". I think it was ex-dairy farm which does not bode well.
    I've replaced the piston and rings with standard size but luckily the bore was ok. I lapped the valves in replaced the cam chain and tensioner and set the clearances but I admit I haven't checked them since. I'm sure the plug is the correct one. The choke is manual and I had a service kit for the carb which I think was standard jets, needle and slider. The idle jet I set at 2 turns out after speaking to the mechanic at Turners who I had the parts off. If its not a daft question which way do I turn it to richen it up a bit. Do the symptoms I describe suggest it is running lean?

  6. #6
    Crap in the fuel tank, maybe? That's what was wrong with my old quad, with those symptoms.
    I cleaned out the tank as best I could (not very well), and put an in-line fuel filter between the tank and the carb. It was a simple fix that improved matters a bit.

  7. #7
    Quote Originally Posted by jimo View Post
    Its a 1996 250 2wd I bought of that auction site "in need of a service". I think it was ex-dairy farm which does not bode well.
    I've replaced the piston and rings with standard size but luckily the bore was ok. I lapped the valves in replaced the cam chain and tensioner and set the clearances but I admit I haven't checked them since. I'm sure the plug is the correct one. The choke is manual and I had a service kit for the carb which I think was standard jets, needle and slider. The idle jet I set at 2 turns out after speaking to the mechanic at Turners who I had the parts off. If its not a daft question which way do I turn it to richen it up a bit. Do the symptoms I describe suggest it is running lean?
    if you want to richen it up turn outwards or anti clockwise.
    I would say it is running on the lean side but you have to determine why air filter jetting or other. pilot jets run to around 2-3000rpm then the mains kick in so it can be pilot or needle setting or even the right needle itlself, one thing at a time though to solve it,atb wayne

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  8. #8
    Try this...

    remove the float chamber under the carb, there's a brass tube that runs up the centre of the carb with a screw slot in the bottom. Remove it and you should be able to see daylight through it (very tiny hole) also check all the little holes in the side of the tube, if any of these are blocked the engine will not run properly. Use a bristle from a wire brush to poke them out.
    The cause of this is stale petrol which smells like varnish and blocks jets.
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  9. #9
    Thanks for all the replies chaps. I don't think it is dirt in the fuel because it has never ticked over well even with new jets in the carb. I'll have a play at the weekend starting with richening up the idle jet quarter of a turn and take it from there.

    Now its back on I'll get you that photo of the rifle rest in use Tim.

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