Ok, I've been a little slow with my updates but the good news is I am way ahead with the project in real life
. Even so, I want to continue to post the findings so I dont just forget everything I have learned along the way.
So the gearset went together without any drama. Surprisingly, all the shift forks were in fine condition. No deep groves or anything to indicate a bent fork. The posts that ride in the shift drum grooves were nice and round with no squaring whats so ever.
Here is a photo of the gear set ready to be installed. From the top are the shift drum, the drive axle (counter shaft sprocet goes on right) and the pinion shaft (clutch goes on left). Once installed, the counter shaft spocket nut will pull the shaft against the counter shaft bearing in the case.
Likewise, the pinion shaft will be pulled against a bearing via the clutch hub nut.
Before closing things up we will have a look at some differences I noticed in the 465/490 engine cases.
Here we are comparing a left side engine case for and 81 YZ465 and a 85 YZ490. The left photos show the outside while the right photos show the inside. Key differences include a modification of the clutch arm area and some beefing up of the 490 case around the transmission bearing. The volume of the crank case was measured to be the same. This makes sense as the crank fly wheels also measure the same and the cranks are in fact interchangable.
Ah another interruption I am afraid... but I am back now!
Here is a little more info on the changes to the clutch arm area. It turns out the clutch arm for 1980 through 1984 models is the same. But then a change occured in 1985 where the shaft of the clutch arm is extended and goes further into the case. The extended casting for the clutch arm is shown in the lower left of the above photo.
The next photo compares the 1980-81 465, the 82-84 490 and 1985 490 and later style cases in the clutch arm area. Side and top vies are shown. The 80-81 case has the short casting. Looking from the top, the bore from for the clutch arm shaft is centered in the casting circle.
The '82 thru '83 (maybe 84?) still has the short casting but adds a screw hole for the countershaft sprocket cover. However, the top view shows
the bore for the clutch shaft is machined off center from the casting circle.
And finally, the 1985 and later case with the extended casting as shown.
Here is a comparison of the early and late style clutch arm clearly showing the difference in shaft length. It is important to use the clutch arm style that matches the case. I later found that the offset clutch arm style (all 490 cases) also requires use of the 490 clutch pressure plate. this late plate has a longer adjuster to make up for the increased distance due to the shaft offset. I will return to this point later in the assembly of my 465 using 490 cases.
The was also minor differences discovered in the shifter shaft where the later shaft was machine down in the middle (weight savings). And finally, the lower picture shows the later vent hole location. The YZ465 case has the vent near the kick starter.