Motorcycle Bottom End Rebuild | Part 1 of 3: Engine Teardown

Motorcycle Bottom End Rebuild | Part 1 of 3: Engine Teardown


Hi, I’m Eric from Rocky Mountain ATV/MC.com. And today I’m going to show you how to split the cases, and to replace crank bearings and a crankshaft. We’ll need some common hand tools, and also some specialty tools made by Tusk. First of all we have our case splitter tool, our circlip pliers, our crank puller/ installer, our clutch hub holder. It also doubles as a flywheel holder. We’ll also introduce some other Tusk tools later on. We’re going to start with the top end
removed, the antifreeze drained, the oil drained. And we want to do a couple things before we pull the bottom end from the frame. What we’re going to do is we’re going to pull the flywheel off, and to do that we need to remove the ignition cover. Remove the clutch cable. And then we’re going to use our Tusk Clutch Hub Holder which also doubles as a flywheel holder. And remove the flywheel bolt. Then we’re going to use our Tusk Flywheel Puller. It’s actually a, you can see it’s a left handed thread. This tool is really important. It’s necessary to get this off. Pull the flywheel. Then we need to go ahead and use our
impact screwdriver. It’s a K&L. It actually makes a really nice to remove
some of these phillips head screws that are in tight. On this bike there’s a little allen head that holds the clutch actuator. Go ahead and pull that out. And then we’re going to pull our stator off. Sit it to the side. Now we’ve went ahead and we’ve
removed it from the frame. We’re gonna start on the clutch side. To start with we’re just going to go ahead and remove the clutch cover. And then remove the outer pressure plate
bolts. Do it in a criss-cross pattern. So there’s no warpage And pull that out, you can see there’s a
spring and the bolt. Go ahead and pull that pressure plate off. And then then clutch plates, both steel and the fiber plates. Now we need to go ahead and remove the clutch lifter. It has a thrust washer on it. And also the clutch lifter rod. Notice how it came out because it needs to
go back in the same way. And then there is a lock washer on this bolt. You’ll just go ahead and pry it off And then we’re going to use our Tusk Clutch Hub Holding Tool Make sure you don’t tighten your holding tool too tight. You don’t want to distort the shape of the clutch hub. Go ahead and pull that off and we’re going to need to be careful and make sure of what’s on the back side. There’s normally a washer of some sort. Next off, the outer basket comes off. And inside that there is a sleeve. A double rolled bearing, and then a washer. We’ll need to make sure that it goes in the same way that it comes out. Next we’re going to take off the outer cover. And when we do this we want to make sure that we pull it off careful. Try not to upset the kickstart gear or spring. And any time you pull of something like that look for washers on the backside. Now we’re going to reinstall the outer clutch basket. So that we can remove the primary drive gear. And we’re going to go ahead and take a soft aluminum washer. And actually wedge it in-between the gears. The aluminum won’t hurt the teeth. But it won’t allow it to spin either. Go ahead and pull the outer basket back off. And then make sure this assembly comes.
Pay attention to how it comes off because it will need to go back on the same way. Make sure there’s nothing else on there. Now we’re going to take our Tusk Snap Ring Pliers and remove our kick-start idler gear. Once again check for washers. We’re going to remove our shift shaft. And then the two bolts that holds our shift pawls on. And when you take this out, try to remove it as an assembly. It’s hard to get the springs back into the pawls for reassembly. Next we’re going to take the star detent off the end of the shift drum. Go ahead remove that. And as you are removing it, you’ll notice on the back side there’s a notch so when you reinstall it, that notch needs to realign with the dowel. Now we’ve got that side done. We’re going to go to the other side. Back over to the ignition, countershaft side. We’re going to remove the case half bolts. Make sure you get them all. There seems to always be a hidden bolt. In Part 2 we’re going to continue splitting our cases using the Tusk Case Splitter. And then we’ll also begin assembly, using our crank puller/ installer.

About the Author: Michael Flood

100 Comments

  1. Best way to get hub off without hub holder I cut my finger pretty bad trying and seeing how lock washer bent up do you have to replace with a new one when you ready to put back together

  2. Most modern bikes are designed like this. The Actuator arm is on the left side of the motor and it goes down into it to push the lifter rod and push the pressure plate out. Other bikes used it on the actual clutch cover like the older YZ125 but that really isn't seen anymore but it's because it's just a better design. Easier to push the plate than pull it and then you don't have to run the cable over there and for other reasons as well

  3. quick question im buying a 92 yz250 and the guy said 4th gear is not working and thinks the shift fork is bent how could i fix that problem i never fixed a transmission problem on a dirt bike before but i always get them running.

  4. You need to split the cases like we have done in this video. Most likely you have a couple bad gears inside and a bent shift fork. When the ears of the gears wear, they pop out of gear easy and can bend a shift fork. I would bet that is what you would be looking at.

  5. question, what is that bearing that goes inside the basket? I have a 2001 that needs that bearing replaced but I coudnt find it anywhere

  6. It will be a double roller bearing or 2 seperate bearings but if you are looking to replace them you should be able to find it on the OEM Schematics for your specific bike and they are almost always found on the "Clutch" diagram. If you let me know what bike you have i can double check for you…

  7. well come to find out the smallest shift fork closest to the crankshaft was sooo worn its possible it could not fully engage the 4th gear.

  8. You didn't show us how to install the crank pin. i want to get this 100% done correctly, so i have to know the right ways. Nice video love the info!

  9. If you pull up the OEM diagrams for your bike you can see which direction the collar faces… It looks like the shoulder portion of the collar sits towards the middle of the motor…

  10. If I'm stripping a motor, I'll leave the clutch cover on and just remove the main cover, one less gasket and 6 less bolts to undo??!! the clutch cover is to service the clutch only

  11. Hello, there seems to be oil leaking out of the exhaust of my yamaha mini enduro 2 stroke bike. Any idea what might be the issue? Or guidance on where to look for problems?
    Nice video btw.

  12. I put my gear shifter mechanism in and then my kick starter in and the other gear but when I went to try to kick start it gets stuck on the shifter at the bottom and that's what is holding it from kicking the bottom gear gets stuck on it , i have a 1996 kx 125 , any help ??

  13. Hey I really need some help with a bbike , its a 1999 cr250 , and I have just put a new crank , all the seals , all gaskets and bearings , new piston and rings , and its burning motor oil , it will smoke really thick and it turns my motor oil black , so someone said my crank seal was put in wrong , so I bought another one and its still doing the same thing , I can't find anyone that knows

  14. It smokes so bad that when I. Park it , it drips oil off the tip of my pipe. , I'm not mixing it to rich or anything , and it acts like it always needs cleaned out unless you run it wide open

  15. I have a 1998 yz 250 is the crank from the 98 the same as a 1999 2004 in specs
     or upgraded? (can the newer model crank be used for a 1998 motor?

  16. If I am just replacing my crank and rod do I still need to take the transmission out or can it stay in?

  17. congratulations on your video from Colombia
    I do not speak English, you only need to see a video to learn more
    thank you very much I wish had had a teacher like ud to teach me a lot more.
    very immaculate your workplace

  18. RockyMountain, quick question. THis will be my first time opening a dirtbike case, I have a great Mechanical aptitude. Does the Head need to be completely taken apart to split the case? rmz250 2013

  19. great series RM, not only you sell quality products at reasonable prices, you also help the DIYs with these great videos. Awesome. 

  20. hey RockyMountain please help me i have this problem with my bike for at least a year now ..this if before i even split my case ….

    my problem.. I know that first gear clunk is normal but this is what i feel when i shift from 1rst to second after that incident. Im happy I dont get grinding as much (maybe once in a while) but whenever I shift from 1st to 2nd, I hear a loud cunk. When i shift it at higher rpm, i have this strange feeling in my feet. Right upon shifting, i feel that the gearbox is exerting a force on my foot (opposite reaction). So when I change from 1rst to 2nd in high rpm, it shifts but there is a clunk and after the shift, the SHIFT LEVER HITS MY FOOT BACK. (Same feeling as bounce a tennis ball against the wall and catching it)

    i have new shift drums, forks, and also like brand new gears…dogs on my old gear was out…..is there something im missing here please help me im going crazy…it only happens shifting from 1st to 2nd….lever hits my foot back but im able to shift it in …ty for taking the time

  21. Rocky ,I have a 2006 Baja 250cc atv ,I need to replace the crank do you have a video of the tear down of the moter?

  22. What do you think about HOT RODS CRANKS and BEARINGS? Please help cause my yz 250 2003 needs this parts replacement and I`ve read a lot and watch some vids, some say that its good quality product and never had any problems and some shout to stay away of it, I would be grateful if you could answer that question. Is it worth to save money buying HOT RODS and worrying about seizing engine or folks just can`t place it properly and thats why this problem appears? PLEASE HELP

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  24. Hi hi! Thanks for sharing! Since you are on the topic of motorcycle; have you done business with " Vidadsmedia Two Wheeler Supply Review " (should be on google…have a look)? My BFF had some dealings with them and was impressed by their super customer service. 

  25. Oh hai! Thanks for sharing! On a separate note; have you ever tried " Vidadsmedia Two Wheeler Supply Review " (google the exact phrase)? My riding buddies had some dealings with them and was impressed by their great customer service.

  26. Hello! Thanks for sharing! By the way; have you considered " Vidadsmedia Two Wheeler Supply Review " (do a google search)? My best friend who is riding fanatic had some dealings with them and was impressed by their awesome customer service.

  27. Oh hai! Thanks for sharing! On a separate note; have you thought about " Vidadsmedia Two Wheeler Supply Review " (do a google search)? My riding buddies had some dealings with them and was impressed by their great customer service. 

  28. Great videos! Helped a lot on my cr. I am doing an rm now and that primary drive gear at 5:38 is giving me a real headache. I jammed that washer in and hammering on the ratchet all night trying to get that bolt to break free but it's not coming. Any ideas?

  29. Thanks for the quick response. It is a 1993 rm125 and I thought it was a 96 originally so I have the 96 repair manual that did not mention anything about a left handed thread but I might try

  30. Me and my dad got it finally it just took a lot of leverage and cranking but thanks for the help I really appreciate it!

  31. A soft aluminum washer didn't work on my primary drive gear. It's over torqued. Any other suggestions? Tried a thicker washer and even a quarter and they all started to bend

  32. well… i have tore apart my 2000 yz426f bike the other day and im great with engines…and to the rookie that doesnt have a hard time remembering where he or she took a part from go this route. if you have a hard time remembering DO NOT remove the kick start gear the it showed him removing YOU DONT HAVE TO… also you dont have to remove the shifter peg either however when you go to put the cases back together it might push out a bit but it will help you align the cases easier… this is a long comment eh. but other than that its fairly simple and can be done by a professional very quickly. it takes me 5 hours to tear down and rebuild my engine top to bottom. it only takes me two to out the whole thing together. also the person i got my bike from had rebuilt it before and trust me it seems like a good idea to beat the crank shaft out of the cases but dont be stupid by the correct tool for that… it isnt expensive.

  33. would this be a good idea if i spun a bearing? 2004 ninja zx10r

    i had a small leak i was unaware of which i believe caused the friction

  34. is it the shift paws what makes the shifter return when switch gear ? i need help because my shifter is loose and when i switch gear it come back to its place it feel like a spring came loose or something

  35. i took out the screws from my honda trx 250 gearbox but it wouldnt seem to come out
    what can i do?? please help

  36. Q.on my honda shadow saber 1100 06.right side there is a noise sound like lose chain.what can you tell me.

  37. Finally ready to do this myself. Good thing I have the same bike. Where can I get the lubricants and bonds that you used in this video?

  38. i purchased some tools from you to assist in removing my engine from a 2001 yz250 and i can't seem to remove the bolt that runs through the lower control arm and engine. am i missing something here?

  39. I just rebuilt my 2000 yz250 when I started it for the first time after rebuild it was like i was holding it wide open and it wouldn't shut off. But I fixed that but it still revs like I'm holding it half open. I'm thinking that there is air getting in somewhere or maybe the sealer that i used was bad idk. I used a hotrods bottom end rebuild kit. Can u please help me?

  40. My primary drive gear is stuck. The washer just gets chewed up by the gears when I try and loosen it. Any recommendations??

  41. i need help, i got a 76 Husqvarna WR250 and i cannot get that gear that runs from the crank to the clutch to save my life. how the dick do i get it off without breaking it?

  42. I just got my cr80r and it won't let me shift up sometimes, what could be wrong, and might changing the gear oil fix it

  43. i got a problem were in first gear it really weak and going uphill it start making a grinding noise on my left side

  44. great video! I have a lot of play in the primary gears on the crank side, what will I need to do to fix the problem?

  45. how much would a shop charge to do something like this? i have the top end taken off my bike already, covers and pates are out but that's it. i have the bottom end rebuild kit also. my local shop charges $100/hr.

  46. Do I have to take all the gears, clutch, and flywheel off or could I leave them on when splitting the case? All I'm doing is replacing the crank. Its an 04 yfz450 which has basically the same motor as the yz450f, yz250f, wr450f and wr250f. Any help appreciated!

  47. so this is a damn good hobbie.im gonna use my spare time and rebuild my ninja 80.im gonna put some special Technics on it to stop it up.ill post pic when I'm done.

  48. my kx85 bottom end went out and im not mad at all because on 2 strokes its easier and cheaper. but i need a left crankcase, top end, bottom end, drain plug, plus the tools that are required

  49. I would like to see a full rebuild and valve adjust on the 2008-09 DS450xmx/xc as the DS platform motor, frame and suspension is a animal all it's own with it's own problems with frame and efi system and no one has anything for it I hope you could pursue this idea for a video set if you choose not to please let me know either way ty I am willing to help with problems I have ran into that everyone seems to be having

  50. What happens if you don’t line up the dowel on the shift drum back to the notch on the star detent?

  51. I have to do it myself on a 125rm the only problem is it's a 97 hard to find parts for I got to find out what other years will match my 97

  52. How do u unscrew the couch spring bolts in 2:59 without having the whole thing spin? I got my engine out of the frame as well and I can’t seem to keep the clutch assembly from rotating when I try to unscrew the spring bolts. I have it in gear too any ideas?

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