Motorcycle Bottom End Rebuild Part 3 (of 3) Final Assembly

Everything You Need To Rebuild Your Bottom End!

How-to disassemble and rebuild the crankshaft and transmission on a modern 2-stroke motocross motorcycle or ATV engine. This is Part 3 of this 3 part engine rebuild series from Rocky Mountain ATV/MC. In this video we cover installing the transmission into the case halve and then applying gasket maker onto the sealing surfaces. Also installing the other case halve and sealing everything up finishing the crank and bearing replacement on this engine. Get all the parts and tools needed for this complete engine rebuild @!

Click Here For Part 1 (Flywheel, Stator & Clutch Removal)

Click Here For Part 2 (Splitting Cases, Crank & Transmission Removal, Crank & Bearing Installation)

Click Here To Subscribe To Our Channel!

Shop All Tools And Accessories Here!



37 thoughts on “Motorcycle Bottom End Rebuild Part 3 (of 3) Final Assembly

  1. I just finished a build on my 1997 rm250 and the shifter moves fine but my bike will not go into neutral… how can I tell if I put the shift drum in correctly

  2. What's it mean when 2 strokes rev by them selves after a crash when the carb is fine I was told it means there's a hole in a gasket on the case.

  3. Thanks a lot for this series. Looked for hours for a free 97 cr125 manual with no luck and than your fine video work gave me my answers in minutes.

  4. hey ive just rebuilt my yz250 04, yet to start it an add gearbox oil but does the clutch actuator arm move all the way up and down like theres nothing there?

  5. awesome ive watched all 3 videos multiple times, im going to give it a go next weekend… What year was this YZ250 btw?

  6. Can I pull the inner clutch cover off of my 2008 KTM 450 EXC without taking out the inner clutch components? Just need to retap the oil check bolt.

  7. I'm attempting my first case crack and rebuild. Will all of the parts/gears/bearings etc. shown here be exactly the same as on my 2001 YZ250? I don't know the names of each part going back in the case and would use the video as a means of inventory when putting it back together.

  8. Good video ! Gah im looking into buying a CR 250 that needs a top end. and im considering just doing bottom and top end and start 100% fresh. But dam it would not be easy. The biggest thing for me is working with transmissions and all the gears and washers.

  9. Hi! Could you do a bottom end rebuilt on a ktm exc 525? My bike has 190h on it, do you think i need to do a bottom end rebuilt on it? It runs great right now. Or is it enough to do a top end rebuilt?


  10. I was wondering if this tutorial works for a 2012 kx 85 and if you could leave a link to all of the tools that are needed.

  11. Hi im doing this on a 1997 kx100 and ive done this with my 2002 yz125 before and I put the 125 transmission in wrong and i believe its because it wasn't spinning freely when i put it in and had to get that done professionally. The kx100 transmission spun freely before i put the other case half on but since i put the other case half on it doesnt spin freely anymore. Is that supposed to happen or do i have to re do it?

  12. My countershaft bearing is giving me a load of trouble. I have tried time and time again to get it to work and also replaced it. The bearing spins freely when it is outside of the case. When it is pressed into the case it has a ton of resistance to spin. Has anyone else had a problem like this?

  13. so….according to the 4 videos I've just watched (1 other was the top end rebuild) and assuming you have all the parts that need replacing, a full engine rebuild would take 2 hours? maybe less? what if the crank shafts is broken? I have a feeling this will be the case on my RS 125 I'm buying to fix up. hmm

  14. You guys make it look so easy, thanks for the step by step tutorial, I feel confident I can do this and refer to the video ,

Leave a Reply

Your email address will not be published. Required fields are marked *