Engine Rebuild

1985 RZ350

1985 California RZ350

I started with a totally bare casing from my box of parts. I decided to build in the transmission off the second motor and sell the original ones from the box of parts as spares for someone else to use..


The first step is to totally clean the casing halves using a detergent such as Simple Green, or Gunk. Check all the casing mating faces and see if any threads are stripped before proceeding further. It would be a bummer to have a stripped casing bolt hole when the engine is almost ready to go back together.


Slide the shifting cam through the hole on the left side of the bottom casing. The far end will fit in a smaller hole in the right hand side of the casing.


Where the end pushes through the right hand side, fit the end cap with the o-ring. Replace the o-ring if it looks worn or is brittle. The cap is held in place by three Phillips head bolts. I used Loctitie on them just to be sure they would not try and back out with vinrations. The cap can only fit on in one way so there is no danger of putting it on incorrectly.


If removed, you can loosely fit the neutral lead screw to the plate, but don't tighten it all the way until you rebuild the stator side of the casing.


The shifter forks are installed next. It is pretty interesting to see how the shifter forks interface with the shifting cam. I hope the pictures I have taken show it clearly enough. Above are the parts you'll need.


There is only one shifter fork on the rod which goes closets to the crankshaft. Find which end of the rod has the groove in it and push the rod through the casing with the grooved end first. Align the front fork so that the casting is bumped out to the right hand side and make sure the foot is in the second groove of the shift cam. Then push the rod all the way until it hits the other side of the casing.


Now find the groove in the second rod and insert it through the small hole in the casing. Grab a second shift fork, but install it so that the casting bump faces the left and the foot engages in the first slot in the cam. Don't puish the rod through as there are two shift forks on this rod.


Place the final shift fork on the same rod and make sure the casting bump faces to the left and the foot engages the final slot in the cam. Now you can push the rod all the way until it hits the left side of the casing.


On both rods, fit a single circlip to the groove at the left side of the casing.


This is just another picture to show both circlips in place.


Now grab the forward most transmission gear cluster. This one can be identified by having a large bearing on the right hand end which has a circlip in a groove around the circumference (shown with the arrow above). This slots into a groove in the casing.


When the transmission cluster is set in the casings properly, the single front shift fork will slide into the center slot of the midel gear as shown above.


Now grab the second transmission cluster and align it so the big bearing at the end is towards the left hand side of the casing. Install the half circle metal piece in the casing groove which will retain the bearing from moving side to side.


The smaller right hand side end also receives a smaller metal half circle before the shaft is installed.


The two shift forks engae into the gear slots as shown above with red arrows.


Above is a close up shot of the two shift forks in the correct position in the rear gear cluster.


I left the cam unsecured during the transmission rebuild just in case I needed to move it slightly...but I didn't. The cam is held in place by a retaining plate which also covers the end of the forward shift arm rod. Place the plate against the casing with the countersunk holes facing outwards. Thenslide it so it engages in the groove around the cam body. Use a little Loctite on the two Phillips head bolts and tighten them down. If you can find Allen head counter sunk bolts they are even better as they are much easier to tighten without slipping out of the slot.


The cam spring and arm goes on next after the small spring as shown above. This keeps the cam in gear.


Tighten down the retaining bolt with a small socket Do not over tighten any of the casing bolts as the aluminum casing can strip easily. Although you can move on to installing the shifter mechanism I was focused on getting the cases back together so I came back later for this step.


The final transmission oil seal can now be installed by slightly lifting on the left hand side end of the rear transmission cluster and fitting it in place. The text should face outwards from the casing as shown above. This completes all the rebuild items in the bottom casing that are required before the cases can be connected.


The upper casing half was also stripped when I got the parts in boxes. Two items are built into the casing upper: the tachometer drive and the clutch actuating arm. Push the tachometer drive axle through the casing hole on the rear right hand side of the casing.


Inside the casing fit the first circlip.....


...followed by the drive gear...


...followed by the second circlip...


..and finally push it all the way through until it won't go any further. Then fit the retaining plate into the groove, add little Loctitie to the screws and tighten it all down.


Fit the dowe through the small hole in the end of the tachometer drive axle.


Fit the plastic drive gear....


..followed by the washer....


..and finally add a criclip to the end of the shaft.


Grease the worm drive, flip the casing over and push it dwon in the hole to mesh with the drive gear.


I secured the drive gear with the plastic retaining piece and bolt even though the tachometer cable wasn't attached....but after installing the tachometer cable later on I realized I put it in backwards (doh). The threaded parts should face out NOT as shown above. .

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