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I'm having a mechanical problem with my 250cc motorcycle. It has 5-gears, and all work smoothly but the 5th gear.

the 5th gear will only work/engage when I shift to it coming downhill on a roadway, from this point it will stay in 5th gear(at least that is what the speed I can achieve indicates) while I'm either continuing downhill or riding along a level surface.

Once I begin to climb an inclined roadway, my motorcycles mechanical system(transmission I believe) enters this unknown state where, though I'm set to be in 5th gear, my motorcycle can't even achieve top speeds of the 4th gear.

Some input to consider when producing a valid answer to my question:

  • I've put +3500 miles on the bike, which was put on riding overt long-distances primarily in 5th gear.
  • It's been about 3,000 miles since the last oil change, and once again, a majority of those miles where accumulated while riding in 5th gear.
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  • So, are you asking about a lack of power in 5th to climb hills? That is normal - you change down just before the hill as the engine only has a small amount of torque...
    – Solar Mike
    Commented Aug 31, 2019 at 19:36
  • No it drops dramatically. As I mentioned in the post, 5th gear it drops well below 4th gear. Also, this isn't just when I'm going uphill, If I attempt to shift to 5th gear, even on a level surface, it can't do it properly. Many times now I have attempted to shift to 5th from the top speed of 4th on a level surface, and the bike just slows down.
    – Colorado_Technical_Savage
    Commented Aug 31, 2019 at 19:41
  • Is this a new bike? What kind of bike is it ... you just state it's a 250cc ...
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Commented Aug 31, 2019 at 20:28
  • 250cc chinese bike. I put about 3000 miles on it out the gate moving it from the south to the midwest.
    – Colorado_Technical_Savage
    Commented Aug 31, 2019 at 20:36
  • can i know the speed and rpm when you want to shift to 5th gear? and what is the max speed and redline RPM of this motor in spec?
    – Cubic273.15
    Commented Jan 3, 2021 at 13:28

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This is really what I would expect to happen. In 5th you have far less torque than in 4th, so under load you will not be able to maintain speed in 5th and should shift down a gear.

The general rule to apply on most bikes, as they have sequential gearboxes is to change down if the bike is not able to maintain speed, or you want more acceleration, and change up if your revs are getting too high or you wish to maintain a constant speed and don't need the extra torque.

I have had bikes that would not go up hills in anything over 3rd :-)

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