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Strange throttle response

Discussion in 'Technical and Troubleshooting Torque' started by n4spd, Aug 14, 2013.

  1. it is a Yamaha Zeal 250, 1999 56,000km.

    on a long uphill if i am going in gear 5, speed is 60-70, reving at 4000, bike will start loosing power before i reach the hill top. the rev stays at 4000, throttle response is very strange, it seems to give a little bit of power but not continuous and consistance. feels like as if i am riding on a buppy road.

    if i shift to lower gear engine will immediately goes off. so i will grip my throttle to get myself to hill top (if lucky), at very low speed around 20 before it stall itself.

    if i come to a uphill in gear 3 this problem does not happen but on a main road with a speed limit of 70 or 80, and it would be very strange to shift to gear 3 and slow down considerably before i start claiming.

    the bike has just been serviced, spark plug, oil, and oil filter changed.

    any thoughts? thanks a lot!

  2. you are in to high a gear, you are to gentle with the throttle
    • Agree Agree x 1
  3. It's a 250, rev it's nuts off.
  4. come on, my first bike is 125, it goes up the same hill no problem, it will feel powerless but the throttle respond as it should, and you can shift down gears anytime if you think it is going too slow.
  5. 4000 is not enough revs! Double that and give that thing some gas!
  6. if i go more than 4000, i will exceed speed limit.

    i don't believe it has to do with rev. if rev is too low it should tend to stall, and you would grab the clutch lever and shift down. this bike is not like that, it would not respond to throttle as usual, and you can not increase rev, there is little power output, and if i grab the clutch lever engine will switch off immediately.
  7. Hi you will need to help us a bit to understand.

    If the engine is labouring and opening the throttle doesn't help change down a gear. The bike will have a particular band of revs where it gives best power. As others have said up in the 8000 range is about right.

    You need to use the gearbox with the throttle to ride the bike. Combinations of gear and throttle for different road conditions. A lower gear and higher revs will give you more power (torque actually) to get up a hill.

    I don't know what you mean by "if i grab the clutch lever engine will switch off immediately." Do you mean it stalls and the engine stops?
  8. hi Chris, thanks, but it will not give me the chance to shift down a gear, the engine will stop immediately if i clutch in. and throttle does not respond properly, it won't rev up, that's why i think something is wrong with this bike, and it only happens at some uphills.

    with this 250 at 4000-5000 it is pretty fast, i weight only 65Kg, i never had to go to 8000. i am going 80km/h, at 5500, in gear 6.
  9. Get your carbs checked float hight, the bowl might be running out of fuel...
  10. If your powers getting loose it sounds like you might have worn out muffler bearings, the power can come loose from around the sides of the bearing once it is worn out.
    • Funny Funny x 2
    • Like Like x 1
    • Agree Agree x 1
  11. Hahaha especially bad if the electronics get a bit of sunspark
  12. hi thanks, but the key is this:

    it only happpens uphill (doesn't have to be steep slope, although the chances will be much higher), at high gear (5 or 6). i will take it to mechanic for a check, thanks again.
  13. why don't you humour us and shift down before you go up the next hill and report back your findings.

    250, long steep hill, top gear, low revs... :banghead:
    • Agree Agree x 1
  14. it doesn't have to be a steep hill, it is a main road, speed limit 60 to 70, then i would think i should be on gear 5, this was ok with my last bike (Kymco 125). should i be going at about 65km/hr in gear 4?

    usually it is :
    a long uphill, or a short steep hill

    one of the long uphill is the one from Eastwood to Carlingford town center, it is not steep but pretty long, everyone is going at about 65km although limit is 60.
  15. it doesn't matter what the speed limit is you use a gear and RPM suitable for the load you are placing on the bike.

    what your other bike did is completely irrelevant.

    Your bike may very well have a problem, but i think most here want to rule out human error first.
  16. thanks, i will do more tests.
  17. i ride mr bike in first at 65
  18. As others have said, use a lower gear, my bike is significantly more powerful and i dont get out of third gear while riding around in sydney at all, and only use the higher gears for motorway cruising or riding fast.

    Bikes are not cars, they love to rev, my bike spends literally hours and hours at 11,000 RPM, eleven, thousand, all day. Thats how bike engines work, you rev them. Ride around in first and second, dont use third unless you redline and are not doing the speed limit, never change up a gear when you are on a hill, ride out the gear then change at the top.
  19. Like I said in your earlier thread its way too low a gear. I agree though it should not stall when you pull the clutch in. At 65 you should not be in a higher gear than 4th and on a slopeyou should really be in 3rd. The zeal likes revs, it has the same engine as the fzr250 which is essentially a race bike. Revs wont hurt it. keep it on the boil. If the problem persists then yes you do have a problem.
  20. #20 smileedude, Aug 19, 2013
    Last edited: Aug 19, 2013
    Sounds like you have a very poor under standing of how gears work. This sounds like normal bike behavior.
    High gear = less torque more speed. Try pushing a bike. It doesn't need that much force to move it. Now try lifting it. Much harder to do. That's what your bike is doing when climbing a hill so you need a lot more torque. Different bikes have different revs to torque ratios. When you have the engine spinning faster it uses more petrol and creates more force. If you're going up a hill with too low revs you are not burning enough petrol to lift the bike up. If you keep trying in the high gear you get the revs reducing as the bike slows so you lose even more power.

    Do you understand blipping the throttle when down shifting? This will make sure you don't lose speed when shifting down. Otherwise it will lurch backwards as the engine grabs the rear wheel.

    You also realise that you need to let go of the throttle when you close the clutch? Otherwise the engine will spin out of control as there is no bike holding it back.

    You should try and downshift before you start losing power.