yz450 drive shaft oil leak

5 replies to this topic
  • gaz7

Posted February 01, 2008 - 02:44 PM


hi i'v got got a oil leak from the dive shaft when running i'v replaced the seal,o ring & new d/shaft bearings still it leaks help:excuseme:

  • 642MX

Posted February 01, 2008 - 02:57 PM


hi i'v got got a oil leak from the dive shaft when running i'v replaced the seal,o ring & new d/shaft bearings still it leaks help:excuseme:

I think your talking about the counter-shaft (shaft that has the front sprocket on it). The collar that goes around the shaft gets worn from the seal. I replaced mine not long ago for the same reason.

  • gaz7

Posted February 01, 2008 - 03:02 PM


hi i'v replaced that as well still no good !

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  • William1

Posted February 01, 2008 - 03:16 PM


If it is still leaking after replacing all those parts, then you have another problem, perhaps a bent shaft or you installed a part poorly/crooked.

  • gaz7

Posted February 01, 2008 - 03:24 PM


my local mx dealer sorted it out they said the shaft woz ok run it for 15 mins at the shop all ok .then with half hour runing it cum back

  • grayracer513

Posted February 01, 2008 - 03:41 PM


Actually, you're both talking about the drive axle, according to Yamaha.

As for your leak, since you say you have replaced the O-ring, seal, and collar, then there are only 3 possibilities:

> You tore the O-ring on assembly

> You damaged the seal, or did not set the seal squarely in the bore (common mistake)

> You misdiagnosed your leak, and it's coming from somewhere else.

Just for fun (uh oh, here he goes again :busted: ), you should know that there is no countershaft in the YZ transmission, or in very many other motorcycles, for that matter. These are simple, two axle transmissions having a main, or input shaft, and an output, or drive shaft. All transmitted power must flow through both shafts.

Countershafts are found in transmissions laid out in the standard rear wheel drive automotive pattern, and in most older large displacement motorcycles. This layout is characterized by having the input shaft and output shafts on the same centerline, and either of those could be the mainshaft. In cars and trucks, the output shaft is typically the mainshaft, whereas with the old British bikes, Harleys, etc, the input shaft is. The counter shaft runs parallel to the other two. In the automotive example, most of the power flow runs through the input, to a pair of gears to the countershaft, through the selected gear set to the mainshaft, and out. There will always be one ratio that is 1:1 (in older cars, this was always high gear, but since overdrive 5 and 6 speeds have come out, it is usually 4th or 5th in those). This is accomplished by simply coupling the input and output shafts together, leaving the countershaft doing nothing but laying there, which is why the Brits typically called that the "lay shaft".

Transverse mounted front wheel drive cars with manual transmissions use the two axle pattern most often these days.

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