my 450 is jumping out of fourth gear

Hi guys ,

I wonder if any one can help me?

I own a 03 450f with about 100 hours on it. it is well maintained.

when I shift up to fourth gear the bike starts to buck in and out of gear, but it only does this in fourth gear, it runs fine in first second and third.

I just replaced the clutch plates both fiber and the steel plates and the pressure plate springs, but this did not help. :cry:

I had the same problem. I when through everything, new chain/ sprocket, new clutch, oil filters and couldn’t find anything. The think that I couldn’t figure out was there were NO metal pieces anywhere in the filters. Anyway, I ended up splitting the cases and when I opened the engine up, there was little pieces of rubber everywhere inside. I'm not sure what these could be from, but they where everywhere. My only guess was one time a while back the valve cover gasket pushed in and that could have chipped away a little in there. Anyway, the inside of the engine looked very good other than the rubber pieces and the sprocket on the crankshaft was hooked like a regular rear sprocket gets. There were no missing teeth anywhere. Everything looks great. SO I’m looking to see what could make my bike slip in and out of 4th as well... I’m assuming that the rubber got in the gears or something and wouldn’t let it shift all the way into 4th. Any other suggestions would be appreciated.


I had the same problem - it just cost me $700 dollars to fix....

Good luck,


You have a bent shift fork It rounded off the dogs on your 4th gear so it's not all the way in gear and it starts chipping away on the gear till it won't stay in gear at all :cry: need to split the case's and replace the two gears and the fork.

I had to replace 1 shift fork and 5 gears because fourth was jumping.


You have a worn 4th and 3rd gear pinion on the mainshaft (the third pinion locks fourth to the shaft when 4th is selected), and most probably a bent #1 shift fork. The fork either bent, causing the problem, or got bent trying to hold the 3rd pinion in enegagement under a load, which it was not intended to have to do. The gears are undercut so that they hold themselves together under loads, theforks just move them in and out of gear, and hold them in place during no load situations, like coasting with the clutch disengaged.

This is assuming it only does this in 4th.

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