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Honda XR200R shifting problem

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Hi every one,
i got a 1984 honda xr200r bike, my problem is actually i can shift without any problem...but in higher gears like 4th and 5th bike doesnt run smoothly.1,2,3 gears are fine i can ride normally, but suddenly when i shift to 4th there is some sound and bike doesnt run smoothly...cannot speed up, bike shaking and clattering.the mechanic told me this can be some bad gear wheels.can some body expalin why this is happening?

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The gears in most all motorcycle transmissions are "constant mesh", meaning the teeth themselves are always meshed with each other.  This prevents the actual gear teeth from being battered in any way by the process of changing gears.  Automotive manual gearboxes use a similar principal, but bikes are much simpler.

There are two shafts, the main and the counter (or, drive and output), and each of the gear ratios consists of a pair of gears, one on each shaft.  One gear of each pair is free to turn independently of the shaft, and the other is locked to its respective shaft on a set of splines.  When you select, for example, low gear from neutral, a shift fork moves a splined gear next to the free gear of the 1st gear pair over against the free gear, and this engages a set of locking lugs on the sliding gear with a matching set of lugs or slots in the free first gear, which locks it to the shaft, thereby connecting the first gear ratio between the engine and the output shaft.  When you shift up, the sliding gear moves away from the 1st gear pair, and either it or another sliding gear moves over against second, locking it in, and so on.

The locking lugs (aka "matching dogs") are made with a very slight undercut, or "dovetail", so that a load placed on them makes them hold together on their own.  As the lugs wear, the undercut disappears and reverses, so that a drive load pushes the two gears away from each other.  Because of the design of the shift fork assembly, the gear cannot physically move the fork to an out-of-gear position, so the fork is flexed enough to let the dogs slide apart enough to slip over one another.  The load is then momentarily lost, and that allows the gear lugs to drop back together, after which the load is reapplied, and the gear skips again.  This will continue as long as there's enough force to make it happen, and it stops once you back off, and will seem otherwise normal when just cruising around.

 

gear.png

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15 hours ago, Ashana. Jackol said:

Hi every one,
i got a 1984 honda xr200r bike, my problem is actually i can shift without any problem...but in higher gears like 4th and 5th bike doesnt run smoothly.1,2,3 gears are fine i can ride normally, but suddenly when i shift to 4th there is some sound and bike doesnt run smoothly...cannot speed up, bike shaking and clattering.the mechanic told me this can be some bad gear wheels.can some body expalin why this is happening?

 

If you shift on through 4th to 5th, what does it do in 5th?

Old School Al

Edited by Old School Al

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If you load it real good (steep hill say)  in 3rd can you by chance get it to do it?  Just to cover the bases........  What kind of shape is your chain and sprockets in ......and how is chain adjustment?  May also want to check the condition of the splines on the countershaft sprocket and countershaft.  Some c/s sprocket don't have deep enough splines and can strip.  Someone hasn't installed a cushion type rear hub that can strip out by any chance.....?  Have you dropped the oil when warm to see if metal is showing up...?    A gear dog problem somewhat as grayracer513 mentioned could very well be the problem, but myself I'd rule out the easy stuff to check first.:thumbsup:

Also I meant to ask.......  Did you just buy the motorcycle with this problem, or did it happen while you've owned it?

Old School Al

Edited by Old School Al
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I too would lean toward a dog problem. But since possibly two gears are involved, maybe a drum or fork problem, maybe even a bent countershaft.  My 1983 CX650 Turbo was making a terrible noise trying to go into 2nd. I remove the trans (a cartridge style trans, no case splitting needed). Upon inspection, found the 2nd drive gear with nearly sheared off dogs, most likely from race shifting by the prior owner. I found a gear back east and replaced it. Shifted correctly with no problems. However in your case, spend $15 first and change the oil to Mobil 1 4T synthetic 10W40 (or Motul, Redline or Royal Purple)  and see if the oil helps at all. If not, then move on to removing the trans.

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My mechanic says that my gear wheels have some big play with shaft, and also some of wheel teeth are cracked, do not have smooth corners.ha said that its better to replace both shafts, not just replacing wheels. :(

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On ‎3‎/‎22‎/‎2017 at 9:49 PM, Ashana. Jackol said:

My mechanic says that my gear wheels have some big play with shaft, and also some of wheel teeth are cracked, do not have smooth corners.ha said that its better to replace both shafts, not just replacing wheels. :(

 

How many million miles do you have on that machine to have that kind of wear...............?  I've seen well used transmissions with some wear, but it didn't seem to cause problems.  Usually you see bent forks / rounded gear dogs which are a result of shifting (stomping) gears under load.

Old School Al

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I concur with Al. Someone has possibly hard shifted and bent the forks or damaged the drum. Manual transmissions are usually problem free, unless abused or lack of oil changes.

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51 minutes ago, HomerDodd said:

I concur with Al. Someone has possibly hard shifted and bent the forks or damaged the drum. Manual transmissions are usually problem free, unless abused or lack of oil changes.

Actually, abusive shifting doesn't usually damage the drum.  It's the clashing of the gear dogs which rounds the dogs and bends the fork.  Once the fork is bent, the gear dogs won't get full engagement, and with rounded dogs now have the total failure of power transmission in that gear.

Old School Al

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