Suspect Transmission

Hi all,

Yesterday I had one of our local Yamaha dealers fit new WR450F gearing into my YZ450F for trails.

All seems well except for one small thing I've picked up.

Lets say I'm at standstill and have the bike idling in gear with the clutch engaged, the bike stands creep, no problem.

If I kill the engine, still holding the clutch in and push the bike forward, the bike feels easy to push for a second (like neutral), then it's as if the gears mesh and you can feel the bike gets more difficult to push.

If you then stop pushing forward and pull the bike backwards, it feels exactly the same, runs free for a second then becomes more difficult to pull.

It feels like there's a lot of "backlash" in the gears. This in itself is not a problem, but, before I had the Transmission changed, the bike felt heavy to push from the beginning in both directions, not this "backlash".

Could someone please let me know if I should be worried and get the bike back to the dealer or is this normal WR transmission behaviour.

Did they replace you clutch basket or any other clutch components?

Normally when a bike is in gear and you're not touching the clutch lever, you can rock the bike back and forth a few inches before it stops in each direction. The back and forth slack you feel before it stops is the slack in the chain, transmission gears teeth and the "dogs" on the transmission gears. Now if you were to repeat the above with the clutch pulled in, you would still have the same back and forth slack as mentioned, but when you come to the end of the slack you would feel the drag of the clutch in both directions. So what you're describing after the tranny work sounds normal. Maybe your clutch was really worn before the tranny work was perfomed and you didn't have any normal clutch drag. That's why I was asking about any clutch work being performed at the sametime.

The dealer didn't do any work on the clutch that I'm aware of.

You do however have a point though, the clutch could be worn because I have been riding a lot of slow technical rocky trails recently, this is exactly what prompted me to have the gearing done. I just assumed that because it's a 2009 model, the clutch shouldn't already be worn.

Is there a way of determining (without opening) if the clutch needs replacing?....... is the "creep whilst idling" test a reliable indicator?

Thanks for the help so far :-)

If your clutch lever is adjusted correctly and the clutch cable is not binding internally, and the bike tries to creep forward in gear after it's warmed up, then that can be an indication of a notched clutch basket or inner clutch hub. If the plates and disc are worn (thinner) then usually it won't creep. But it can slip when riding, especially the harder you accelerate.

It doesn't creep and I haven't noticed any slip during acceleration.

The more I think about it, the more I think you hit it on the head with your explenation about the gear train ie. slack chain, gears, gear dogs.

I think I was maybe just a little "sensitive" because I'm not mechanically inclined, I'm even doubting what I said earlier about there being "no slack" with my stock transmission. I can't honestly say I paid any attention to it before.

Thanks for your help, it's much appreciated.

Wishing you the best for 2010.

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