Modify the pinion bearing block

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Raptor 30/46/50
This modification is to increase the tension on the pinion bearing. If you notice, when you have the engine out, that the clutch bell can wobble back and forth a lot (MORE THEN 2mm PER SIDE) then do this mod to stop that. It is possible a bad bearing could be the cause of the wobble, but this is almost always due to the grip of the bearing block.
Also before trying something as drastic as trimming the frameset you might want to putting a layer of glue around the outside of the bearing.
remove glow plug extension - if you use one
remove fuel line and pressure line - I usually take the pressure line loose from the tank side so as to reduce stress on the muffler end of the tubing. This area has a decreased lifetime due to the high heat.
take off the muffler - it is held on with two bolts
remove throttle link - page 15, step 17, item 5
remove the four bolts from engine mount - page 10, step 10, items 1
take out engine - the engine, fan, and clutch all drop down together

remove start coupler - held on with two set screws
remove start shaft - if the shaft does not easily slide through the bearings then it probably because the set screws caused the shaft to bulge out and make it too big to go through the bearings. You can use a dremel with a grinding stone to grind down the bulged area. I recommend placing a paper towel over the shaft and poke the shaft up through it so that the paper towel catches the grindings. You don't want the metal grindings to get in the top bearing. BTW: Do not try to force the shaft through the bearings, you will end up pitting the bearing races.

remove screws in pitch arm - page 8, step 6, item 2 and 3. The bolts have collars on them that you don't want to lose. Also the bolt on the right side has a small washer. I usually place a small diameter piece of fuel tubing on the end of the screw to keep from loosing the parts.
remove collective link - page 15, step 17, item 6
lift pitch arm off and hold up out of the way with a rubberband
remove screws in bearing blocks all the way back to the main shaft - remove all the screw in this area that keep you from spreading the frames
spread frames - the plastic flexes enough for you to get the bearings out.
remove top bearing and pinion bearing - page 6, step 3, item 2 & page 5, step 2, item 1
Trim plastic from bearing block - use a dremel and cut 1mm from each side of the bearing blocks. I colored this area red in the picture.

reverse order to put it back together, some things to note are:
+start shaft installation - you have to push it up all the way. If you look at the bottom of the shaft the top edge of the big end should be up against the bearing. in the clutch bell. And when you put the start coupler on make sure you get the flat sides in the top of the shaft aligned so the set screws will engage them. Use blue loctite on the set screws. As you tighten the set screws you need to push upward on the shaft and downward on the start coupler. That will eliminate any up/down play in the shaft.
+engine alignment - I use the start coupler to tell me if the engine is aligned. When you rotate the start coupler counter clockwise it should spin with little to no resistance. I twist the engine left/right or twist forward/backward until I can spin the start coupler backwards and have little to no resistance. In some cases I have to increase the size of the bolt holes to allow me to angle the engine just right.
+install muffler - If the bolts thread into the muffler then be sure to use some blue loctite, if the bolts extend through the muffler exhaust flange and go into some nyloc nuts then do not use loctite. After the first tank of fuel, retighten these bolts while the engine is still hot.