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Crankshaft Rebuild Walkthrough


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My 2 cents...

I will start off with a little info and my experience. I am not an expert! I recently got into banshees and enjoy working on them! I am adding this to help anyone like myself who likes doing things themselves and learning in the process. I searched all over the web and here and found little information on rebuilding a banshee crank. I have rebuilt a few single cylinder dirt bike cranks years back, but this is my first banshee crank rebuild! I am currently a design engineer for an orthopedic company. I also have a lot of tuning, machining, and fabrication history with cars, motorcycles, and boats. I also use and have access to a lot of CNC machining and fabrication equipment. I know this is not something your average banshee owner will mess with, but it may help a few people with the process or help them decide whether they should attempt it. This rebuild is for a Hot Rods crankshaft.


I will edit and add things as I can.


I have condensed the disassembly steps into one post. I also made changes to some of my other posts for editing and condensing. This will help keep this close together for reading later.


I have now completed the assembly steps.

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  • A flat and clean work surface
  • A set of calipers (8 - 12 inch preferably, larger calipers make it easier to measure the crank web spacing)



  • Depth Micrometer (used for measuring crank web surfaces)



  • Precision Shims ( I use a kit with various diameters and thicknesses .001",.005",.015",.032". You should be able to stack different thicknesses together for heights from .001-.050")



  • A dial indicator for measuring runout



  • A pair of V blocks (large enough to hold crankshaft without bearings - I use a set of 1,2,3 blocks as spacers) Note: I would normally use a lathe with the crank mounted on a set of live centers but not everyone has a lathe so I will show the process with V blocks.



  • A hydraulic shop press w/ a pair of cross bars (you will need some additional cross bars to form a box under certain areas)



  • A bearing puller ( I made my own and find it very useful. The splitter type puller makes contact with the crank and can also damage the center labyrinth seal. I'll give specs on my puller later)



  • Bearing inner race press tool ( Nothing special here, I used a piece of 1 inch pipe and squared up the faces. Make sure the ends are square and clean of burrs and debris. Its best to have a good chamfer on the edges)



  • A crank web press plate ( I ended up milling two cut outs in my plate. The small cut out should fit on the inside of the crank webs, on the thin flat areas around the crank pins. You can make a template using thin cardboard to get the shape right. The larger cut out is used around the bearing stack when pressing the crank back together. My large square cut out measures 2.480" x 2.480")






  • Crank Phasing Fixture



  • Dowel pins, bolts, etc. (used to press out the center shaft and rod journals)

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Using bearing puller, remove the clutch (PTO) side outer main bearing.





Repeat process and remove stator (MAG) side outer main bearing.





Using crank web press plate. Place stator side outer crank web onto press plate with rod journal centered in the cut out. With the stator side web supported by the plate, press the crank and rod journal out of the crank web. (Notes: The rod should be facing away from the cut out. Also make sure the rod will not contact or get caught on anything as it pressed down. Be sure to hold the rest of the crank. Don't drop your crank underneath as you press it out! You can use tape to hold the web up top and keep it from jumping off the press.)









Now repeat this process on the clutch side of the crankshaft and press the clutch side outer web off.


Next place the stator side inner web on the press using cross bars. Press the center shaft out.






You should now have something like this.




Now take the remaining center and remove the o-rings off the bearings and labyrinth seal.




Install bearing puller on outer bearing and press it off the center shaft.






Remove labyrinth seal and install the bearing puller on the last center bearing.








Press the remaining bearing of the center shaft.






Now using the crank web press plate. Press the crank pin out of the clutch side center web.








Using the same method press the crank pin out of the stator side center web.










Disassembly is now complete.



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Also everyone who has a crank lying around please help me out! I need some measurements taken of the crank web outer diameter. Trying to make a tolerance range on my fixture which will work on most cranks. This would really help with the specs I will provide for making this fixture and ensure it will work on other people cranks.





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Preparation for Assembly

1. Clean up all your parts. Make sure there is no grease, metal shavings, or burrs on the interference areas.


2. Measure all your components.


Measure your crank pins
and record their lengths. My pins measure 2.072" and 2.074". Mark them with a marker so you can tell them apart later. (My old crank bearings and crank pins were worn out so I will be using new parts.)





You can use calipers for this part if you don't have a 2-3" mic. Micrometers are just more precise.





I am trying a set of NTN 10 ball max load bearings #BL305NR. I just try to stay away from chinese bearings. Taiwan bearings are fine, but I prefer Japanese bearings.




Measure your bearings. Its good to record there widths and you will need to know the inner race size for pressing them on. I just used a piece of 1" pipe with the edges squared up and chamfered.







Measure all of your crank web lip heights and record them. You will need to know these to determine the correct shim heights when pressing them back together.
(Again calipers could be used if thats all you have
but a depth mic is best)



Stator side outer web was .0435"


Stator side inner web was .020"


Clutch side inner web (center shaft) was .0155"


Clutch side outer web was .038"


Measure the both the stator and clutch side crank web width from the outer lip to opposite side crank pin surfaces.





I forgot to measure my inner webs. It would be best to get the clutch side inner web center shaft to opposite side height now. As well as stator side inner web. The inner webs measure from the center where you will be pressing the crank. I took my measurements later but it was a pain.

Here is a drawing showing the measurements and shim heights I used.





3. Inspect your center labyrinth seal. My seal had wear areas on the cog surfaces with metal burrs flaking off. Don't want those pieces going into the bearings or engine! I filed off all the burrs and reused it.



Burrs on worn surfaces of cogs.



All edges filed smooth and cleaned up.



4. You can install the orings onto your bearings and seal, so you don't forget and have to put them on after its pressed together.




Ready to press it all back together now!

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Assembly Part 1 ( Inner Halves )


1. Using the crank web press plate. Press the crank pin into the clutch side inner web.



.015" shim

Place the appropriate shim size under the pin.



Should look like this.


Verify press height. (perfect .015")



2. Using the same process, press the crank pin into stator side inner web.



Note: Try to get your press cross bars as close together around the parts you are pressing together. This will prevent flexing and allow you to get the proper press height with your shim.



Place the shim under the crank pin (.015" shim)



Should look like this.


Again verify the press depth on the crank pin.


If you are welding your crank, you may choose to weld the crank pins in place at this time.


3. Now using half of the crank fixture, press the first bearing onto the center shaft of the clutch side inner web.







Note the location of the o ring groove. It should be on the top side of the bearing.



This bearing should be pressed all the way down until it bottoms out on the web.




4. Place the labyrinth seal on top of the bearing.





If you have a single oring labyrinth seal the bevel should face down towards the clutch side inner web. (Some seals have 2 orings and are symmetrical).



5. Now partially press the second bearing onto the center shaft. This bearing will NOT be pressed all the way down!



Note the bearing oring groove location is facing towards the labyrinth seal.




Leave a gap between the labyrinth seal and the bearing. Approx. .030"-.060".



Bearings installed.



6. Using the full crank fixture, press the stator side inner web onto the center shaft. Take your time here. This is the most crucial part of the crank assembly!



You should have already taken these measurements and determined a shim to use for the correct press depth.
Refer to the drawing in the Assembly Preparation portion if needed.



I determined a .0215 shim would give me the correct spacing. If needed press with a larger shim height first, then check your inner web spacing to determine how much smaller your shim needs to be for correct spacing.




Place the clutch side inner web in the lower half of the crank fixture with the center shaft pointing up. Next place your shim on top of the center shaft. Then place your stator side web into the top half of the crank fixture and lower in down until it contacts the center shaft. Make sure the shims stay centered on top of the shaft as you lower top fixture and web down into place.




Now press the center section together until it bottoms out on the shims.
The top bearing should make contact with the stator side web during this press and the remaining gap should tighten up to the correct height.



Here you can see the shims on top of the center shaft after the press portion has been completed. These shims bottom out between the top half of the crank fixture and the center shaft.




Remove the completed center section from the fixture.





7. Verify the the web spacing. I didn't get a picture of this but inside to inside web measurement should be 1.891"




8. Now check the crank phasing. I did not get a picture of the process I used. But have added a model to show how I checked my phasing.




My crank phasing measurements were .002" different. This is within tolerance and equals approx 1/10th of a degree.


The inner half is now complete. Note: If you are welding you may choose to weld the center shaft at this point.

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