Motorcycle Bottom End Rebuild | Part 2 of 3: Crank & Bearings
Motorcycle Bottom End Rebuild | Part 2 of 3: Crank & Bearings


This is Part 2 of the Split Cases, Crank and Crank Bearing Replacement Video. Please refer to Part 1 for the previous dis-assembly. Using the Tusk Case Splitter. We’re going to go ahead and put this on the ignition side. And there’s a couple important things to remember with this tool. First of all it needs to be level with the case. So the tool pulls it level, and it also needs to be centered on the crank. And the bolts don’t need to be tight. You don’t want to damage the sealing
surface because the pressure will not be on the case half. It will be actually on the bolts. And you go ahead and use a ratchet. And start to press that
splitter and you can see that it’s starting to split the case. And you want to make sure that the case is coming apart parallel. If it doesn’t sometimes you need to take a rubber mallet and tap the backside. So that it comes out together. You don’t
want it coming off at an angle. It needs to all come out parallel. Once you’re done with it go ahead and remove the puller. And pull your case half off. And as you do this you want to make sure that there’s no washers that have stuck to the inner races of the bearings on the other side. So you don’t misplace them. And now you can see everything exposed, there’s your transmission and your crank. We’re going to go ahead and pull the transmission out. Get your countershaft and your main shaft. Make sure and try to keep
them all together. All your shift forks And then lay them out. Make sure and check for washers, and your shift drum also. Now’s a good time to check for wear on your cogs. Now we’re going to go ahead and push the
crank out from the other side using our splitter again What we’ve done is we’ve mounted this to the clutch side, and we’re just pushing that crank out. As you can see it comes out nice and straight. Make sure
once again that your puller is centered on the crank. We’re going to inspect our rod. At this time. Now side to side movement is OK but it’s just the straight up and straight down movement is what you want to check for. And if it is loose. Pro-X or Hotrods makes a complete crankshaft assembly. Or you can have your crank rebuilt by a machine shop. Now it’s time to remove the crank bearings and seals. To start off with we’ll remove the seal retainers And we’ll flip it over and use a punch or a screwdriver and pound that seal out. We also want to remove the centering
dowels. So we can lay the case flat on our clean work area. Because we don’t want to mess up the sealing surface of that crank half, the case half. Use a large socket. And pound out the main bearing. It may take some considerable force. We’re going to go ahead and clean it up at this point. We want to make sure and get some new quality bearings to install. And what we need to do is we need to use, it’s called sweating it in. And you heat up the case half and then you’re going to freeze the bearing. And so we want to heat this up, we’re just using a propane torch. You want to heat it up until water just barely sizzles. It’s about two hundred degrees. And we’ve had our bearing in a little cooler with some dry ice to shrink that bearing up. You want to use some gloves to protect your hands. This bearing is very cold at this point. We want to wipe off the ice so this slides right down in there. There’s some condensation that’s formed and some ice. And you actually just drop it right in. And if you’ve done it right it should just slide right in. Now we’re installing our seal, our crank seal. But it might be a good idea to do this later and you install the crankshaft. Here is the seal retaining clips. Use some medium strength threadlocker on them. You don’t want any of these bolts coming loose inside your case. We’re lubing up the outside of the seal for the other side. And this also, you can install the seal after your crankshaft has been installed. Here’s all your parts laid out on your clean work area. They’re in order, they’re organized. We know how they’re going to go back in. Alright we’re going to start to install the crank. We’ve got our new bearings, were gonna go ahead and grease up the inner surfaces a little bit. We’re going to go ahead and sit the crank in the bearing. And flip the case half over. And install the crank installer. And there are several parts, adapters that adapts it to the end of your crank. There is an aligning notch that this tool goes down onto. Put the nut on the outside. Thread that on a little bit. Some cases you can actually just rest the puller down on the case just outside the bearing. But on this model we needed to use some bar stock. To hold it up and away from the boss’ that were interfering. The bar stock just holds it parallel to the case. Where there’s no interference. We’re gonna go ahead and start tightening the nut which will pull the crank in. And you want to make sure that the rod is up or where it needs to be so it doesn’t interfere with You’re going to go ahead and tighten that, and it pulls the crank all the way in to where it needs to be. This concludes Part 2. Please refer to Split Cases, Crank and Crank Bearing Replacement, Part 3, for additional assembly instructions.

100 thoughts on “Motorcycle Bottom End Rebuild | Part 2 of 3: Crank & Bearings”

  1. BloodOnMars says:

    Qestion! How do you know how tight to tighten the crank. Can you do damage if you tighten it to tight?

  2. Franke Diamonds says:

    Am i able to ship a 2001 honda cr250 motor to have the crank, bearings and piston changed out? you guys look like yall know what the hell yall are doing. Im scared to try this on my own and even more scared if i give my motor to someone else they will even do the work. [email protected]

  3. Rocky Mountain ATV MC says:

    Sorry but unfortunately we don't offer this service so you have a couple different options. If you were to follow this set of videos and have your service manual right there for reference i'm sure you would be fine doing the split but your service manual and the correct tools are key to a succesful job. If you don't feel comfortable doing the split one of your local dealers or local shops would be the next best option.

  4. BloodOnMars says:

    4:10 what did you spray to clean the cases?

  5. Rocky Mountain ATV MC says:

    We were just using an aerosol contact cleaner but most times we'll clean each case half in a parts cleaner

  6. Irish outdoors says:

    hi,i have a kxf 250 06 and i think my main bearing may be gone,picture this im kneeling down putting the front sprocket on and notice play in the shaft,it goes in and out slightly,if i rock it up and down theres no play its only in and out theres play,not a whole lot tho?

  7. isaiah essex says:

    hey I have a 2006 yz250 and I was just wondering what tools I would need to fix my bottom end 5th gear is done and I never done the bottom end before so its my first

  8. Rocky Mountain ATV MC says:

    Just follow these videos and your service manual very closely. You'll need a few different tools such as a flywheel puller, case splitter, crankshaft install/ puller tool and then also a clutch holding tool.

  9. OlivierV9000 says:

    Nice instructive vid thx for that !!! Just to be sure… how long do you let the bearings cool down in dry ice & how long should an average warmin' up fase of the crankcase take with a propane torch? I tried to warm up mine with a heat gun and the bearing got stuck half way.. had to get it in with a hammer and that killed the bearing 🙁 …. thx

  10. Rocky Mountain ATV MC says:

    The bearings and crank will get to a point where it's not going to let you pull it together anymore. You'll feel it when it stops and you won't be able to go anymore. Obviously you don't want to crank on it super hard but also as you put your other case half on it will put the crank where it needs to be

  11. Rocky Mountain ATV MC says:

    Usually i will put the bearings in the freezer overnight so they are good and cold and then pull them right before you and going to set them in. When heating up the case half i will go around it with a torch for a few minutes to the point where water will sizzle as shown in the video. Alot of times the bearing will drop right in with a little assembly grease but if it doesn't drop right in don't hit it directly on the bearing.

  12. Rocky Mountain ATV MC says:

    I like to use a bearing driver set but if you don't have access to one a socket that sits on the outer race works just fine. Just watch and make sure the bearing goes in straight.

  13. twistedfocus100 says:

    My bearings stayed on the crank. Any tricks on pulling them off of the crank?

  14. Rocky Mountain ATV MC says:

    The only way to get these bearings off and not jack up your crank is to use a bearing puller. We sell a Tusk Crank Bearing and Gear Puller Set for $59.99 a piece. The part # is 1195970001. You don't want to hit and pound on your crank at all so a bearing puller is by far the best and easiest route to go.

  15. vagelis priftis says:

    Hi man! I like your work! I please you, can you find a cylinder from yamaha yz 250cc with 4da00 249cc? If you can find it communicate with me in Youtube in my profile and tell me how it cost and if you can send me in Greece. I search it in Greece a lot of time and I will be very happy if you can send it to me! Thank for your time which waste for me!

  16. Guy Garic says:

    what an echo at 4:00

  17. Guy Garic says:

    thats a two stroke, right?

  18. Rocky Mountain ATV MC says:

    Yes this video is of a YZ250

  19. Rocky Mountain ATV MC says:

    Thanks! That is the Bel-Ray Waterproof Grease, We carry it in a 14 oz. Tube (1043410001) and also the 16 oz. Tub (1043410002).

  20. dblock2626 says:

    Hey could I not just use a shop press to push the crank into the bearing?

  21. Rocky Mountain ATV MC says:

    You could do this for the 1 side but it's critical that the crank goes in straight to avoid causing any damage.

  22. dblock2626 says:

    For the other side it will pretty much handle itself when I go to put the case back together using a criss cross pattern it should be fine sliding the crank into that side by tightening the cases correct? U don't really need any tusk tools right.. I mean what did they do years ago before tusk was a company.prob help a lot to have them but don't absolutly neeed them

  23. Rocky Mountain ATV MC says:

    That is correct, you can do a rebuild without the help of the Tusk Tools but they sure do make the job a whole lot easier!!!

  24. dblock2626 says:

    Cool man thanks I thought so but had to be sure

  25. Rocky Mountain ATV MC says:

    Not a problem!

  26. jarred dell says:

    You would be more successful if you got a socket big enough to get on the outer race of the bearing , then pound or press them out

  27. dirtbike whip says:

    does it matter which side of the crankcase i install the crankshaft and transmission into first?

  28. Rocky Mountain ATV MC says:

    Nope it doesn't matter, you can install them into either side. I will usually start with the right side and work from their but it's basically up to you to start with whatever side you think is gonna be easier. On some bikes if your crank puller only fits on one side of the crank it may be easier to heat the bearing and freeze the crank and install that side first and then use the puller tool to pull both cases together. Other than that it's totally up to you

  29. Nicholas Sabourin says:

    if i have up and down play with my connecting rod, does it mean I need a new crankshaft bearing. Or is there a way to tighten the connecting rod?

  30. Rocky Mountain ATV MC says:

    You don't want any up and down play in the connecting rod so you have a couple options… depending on the bike you have some cranks are easier to rebuild than others but a lot of times you have to have a shop do it. You would need to buy a new connecting rod assembly if you go that route… If not you can just buy and entire crankshaft assembly which already comes balanced and assembled but it's up to you…

  31. Okipouros says:

    I wonder if you could assist me with this:
    The 560, has one deep groove, and one roller bearing, since it has a ball bearing, how do you set the axial play to spec?

    Great vid, I do the same stuff, only that i stick the crank in the freezer so it drops right in

  32. Rocky Mountain ATV MC says:

    If you are refering to a KTM, they sell thin spacers (thrust washer) for the crank (between crank and main bearing). They sell them in different thicknesses to adjust the play. Check the OE parts diagrams on our site to see the spacer options.

  33. dirtbike whip says:

    I did this bottom end rebuild and after me bike didnt run right, I pulled it apart and the cylinder has wore out of round. I also noticed that the crankshaft is all the way to one side of the crankcase, is there supose to be an even gap on both sides of the crankshaft and could this be what caused my cylinder to get out of round?

  34. Rocky Mountain ATV MC says:

    Most dirt bike cranks don't require shimming; rather, the crank needs to be pressed together with its width in spec with the tollerences in the service manual (Some KTMs do need shimming). In most cases, the crank will always be pulled to the right side (primary gear, bolt and spacer are all tight). Regarding your cylinder, I am not sure what you have going on. side to side or front to back? Typically, there is enough side to side play in the rod to put any side pressure on the piston.

  35. dirtbike whip says:

    It is warn wider side to side, when i put the ring in the cylinder it only touches in the front and back and its a 2005 cr125 if that matters.

  36. M Baggie says:

    So many of these engine rebuilds dont include replacing the transmission bearings. I guess its because of the cost of the bearings. Most people dont know that you need not buy bearings from the Bike manufacturer or parts distributor. Most of these bearings are standard bearings that can be purchased for a fraction of the cost.Typical example would be replacing the main shaft bearing on a KTM125. If you buy it from KTM expect to pay around £15.00 plus carriage. You can get the same bearing off Ebay for £1.84 and that includes delivery.

  37. M Baggie says:

    Oh and another thing. Dont bother spending nearly £100 on the tusk crankcase splitter. Just buy a harmonic balance puller for approx £10 on Ebay. It will do the same job. When reassembling the crankshaft. You wont need a Tusk crankshaft puller either. Put the crank in the freezer for an hour and put the case half in the oven 150 degress for 15 minutes.Crank will slip in without problems.Fit the oil seals after the Crank is installed. Use the case half bolts to pull the 2 Crankcase halves back together. Cheap as chips to do your own engine rebuild. Dont bother buying gasket kits either.Too expensive. Buy A4 gasket sheets for a couple of quid and cut your own.Plenty of vids to show how to make your own gaskets for a fraction of the price.

  38. sony xray says:

    I had a watch band like that when I was a teenager

  39. NL Snowboard says:

    what bike does this motor come off?

  40. Magnetic.Crayon says:

    Is it possible to push the crank bearings in to far? I dropped them in and then gave them a little tap and when they warmed up they were difficult to spin. Its a kx 250 so the crank seals go in before the bearings so to tap them out would mean destroying the seals would it not? Is this normal? If I finish re assembling the motor will it correct its self during the first run? I do have the case halves together already and I dont wanna go back and redo it all lol

  41. Mr-Cody Grimes says:

    When installing crank seal , make sure its nice and flush , or it will leak

  42. JEFF STONE says:

    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
    esto lo hice por medio del traductor google

  43. Bala Customs says:

    What year is this ???

  44. Bala Customs says:

    What year???

  45. Bala Customs says:

    Is the engine set up the same for an 03 ? Cause I was having some trouble getting my gears out, I think the shift drum was just stuck but I'm not sure

  46. Bala Customs says:

    Ok thanks, I already got them out. The case was cracked so I was putting everything into a new one and I had to cut the old case because she shift drum wouldn't break free from the bearing

  47. bobmcgoober27 says:

    IDK if youknew, buuut RMZ is 4 STROKE!!!

  48. John Basson says:

    excellent video , Thanks !!

  49. Cody Michler says:

    28 thumbs down? this video is probably one of the better videos out there. Great video 😀 much help to me!

  50. phdequipped says:

    We are rebuilding an 06 kx 250. The crank seals come out to the inside. As a result heating the case to insert the bearing could be detrimental to the seal as it must be placed first. Got any ideas? By the way, THANK YOU for this vid. We rebuilt a 90 CR 500 successfully because of you!

  51. Michael Chappell says:

    So what do you do it the lower rod where it is connected to the crank is seized? How do you remove it if it won't spin like in your video?

  52. Yasin Abdul says:

    I have a question. I have a 1984 Kawasaki KDX250 and I need a part #21007 STATOR GENERATOR MAGNET ROTOR and I can not find it online anywhere at all. It's actually obsolete. Will another later model work on my bike to get it up and running again? If not, what should I do?

  53. stevecon82 says:

    Great Video lots of help. I'm rebuilding my 05 YZ250. I had to replace my left main case and am having problems getting the bearings to seat.  Tried the torch trick and freezing the bearing but no go they wont seat all the way. Now I'm stuck with one of the transmission bearings half way seated. Any idea how to remove it or get it to seat the rest of the way. ( can't beat it out from the back side ) I didn't have any issues with the right case all the bearings went in easy.

  54. Codie Bell says:

    At 3:55 could sombody give me a name or part number for the small bearing above the one he is knocking out ? I need on as mine is jammed in there on an angle somehow…

  55. D. Ryan says:

    Hey Rocky Mountain I have a question. Ive replaced the crank and crank bearings on my 2010 kx250f. Bearings sweated in nicely along with crank. Also used a crank installer to make sure the crank is seated all the way. My problem is the crank spins freely but as soon as i start to tighten the crank case bolts squeezing the cases together the crank seizes. Any ideas about how to fix this ?
    Thanks

  56. Ronnie Godfrey says:

    When re-installing the crank how do you know when it has been seated properly into the crank bearing? How much force do you apply without over torquing it into the crank bearing?

  57. Travis Vincent says:

    tusk this tusk that…this job is simple wo the special tusk tools…

  58. Narayana23597 Yagna says:

    which bikes engine did you remove

  59. Narayana23597 Yagna says:

    can you get me a video of a complete dismantle of new version engine

  60. Honda XR650R Freaks says:

    You're doing a excellent job… Thanks for the helpful video.

  61. Rico Matic says:

    low rocky m0untain what is size the transmisi0n bearing and other bearin inside engine a h0nda tmx 155cc

  62. Warrior Nutrition says:

    can i use regular ice to chill the bearings rather than dry ice?

  63. Warrior Nutrition says:

    ok thx for the advice.

  64. Logan says:

    what is that material you spread on the crank and the bearing called?

  65. MrJohnnyJohnster says:

    Great, I just spent the last half-hour trying to pull my bottom end bearings out of the case with a slide-hammer bearing puller and this joker comes along and shows me how to do it in half a MINUTE. I don't know whether to thank you or kill you.

  66. Brandon Quenneville says:

    TIP- weight the frozen bearing with 1/2lbs for five min. After dropping it in the case of course.

  67. Sled_NeckX99 says:

    Is the case splitter required

  68. Sled_NeckX99 says:

    Is the process at least anything like a Yamaha TTR 110cc

  69. javonte johnson says:

    having a problem splitting my yz250 case open. when I use the crank case tool it gets harder to spilt the case each turn.

  70. Aldean Louis says:

    hi. these are very informative videos. nice. I have to get to my transmission of my 2003 Yamaha wr 450f as the bike is stuck in 3rd gear with the shift lever stuck down.
    do I have to take the engine off the bike to do so?

  71. Kenny Skjæveland says:

    do you have to remove the transmission to change te crankshaft on a Honda crf 250 2008 anyone??:)

  72. Tyler Davidson says:

    what kind of grease are you using on the bearings? at 6:10

  73. William Todd says:

    when re-installing the crank you used bar stock across the case doesn't that mean the crank installer is pulling on the crank / inner race of the bearing only? it should be holding the inner race and pulling the crank into it. I love your videos but had to close my eyes for that part

  74. luke mccosby says:

    do you have to have that tool to install the crank

  75. Devon Brown says:

    Great video! I am currently rebuilding a 2008 KX250f. I have the motor pulled out and piston removed and oil drained. Bottom end is on the bench. When I rotate the rod/crank by hand, there is a slight clunking sound. It rotates smoothly but there is still a noise. Is this the main crank bearing? There is no free play up and down but a little from side to side of the rod. The clearance free play from side to side is 0.35mm (between connecting rod and crank), standard clearance is 0.25mm-0.35mm and service limit is 0.55mm. This is my first bottom end job so I'm not sure if the rod/crank should rotate with no noise at all. Also, my service manual states that you should not use a torch on the case as it will cause warping. Is it still okay to sweat bearings in as long as you don't heat it up too much (above 200F)?

  76. TiTs McGee says:

    dont install the crank seal backwards lol

  77. Joseph Aznar says:

    rockymountain why not replace all the bearings ? mines has a knocking sound on the yz125 change top end but still knocking..

  78. Taylor Anderson says:

    A rubber mallet doubles as a crank installer so save the money

  79. Robert Flowers says:

    my crank shaft is blocking my clutch from coming out in my baja dirt runner 125 cc and there isn't a bolt to take it out any suggestions???

  80. Thisisaj14 says:

    Well how would I do it on my 1983 KX500? It has the seal on the inside like the bearing.

  81. mareksozols says:

    i think that the crank puller needs to be redesigned to rest on the inner race, this way it will not exert exessive acial force on the bearing during assembly.

  82. Josh Slone says:

    Heat a socket that will slide in the bearing, it will fall in trust me.

  83. keeping it real says:

    hello great vid in the process of building my bike and this is helping alot, im just curious tho as to why you didnt change the other bearnings left in the crank? is it because they didnt need to be replaced? should you just replace every bearnings if your splitting the case? thanks in advance!

  84. Brandi Meeker says:

    what year bike was this

  85. Andy Jonson says:

    When you pull the cranck in with the Tusk tool, how far in ( to the side of the case) do you pull it?

  86. cecilyt006 says:

    like a boss, yo.

  87. diego paloschi says:

    Hi friend, could you answer me if the crankshaft of the YZ 250 2001 is compatible with the YZ 250 1998? what would be the differences from one to another and would have how to modify something to use it in the yz 250 1998 thank you.

  88. tonymarcuso says:

    Hi, i love this video, really well explained, looking for the same one for Honda nsr 125 jc22, somebody's got any idea

  89. Adam Chevrefils says:

    Quality bearings – Uses Allballs –

  90. Oklahoma Fool 2 says:

    What do I use if I don’t have a case splitter

  91. RideArizona says:

    Thank you for making this video 👍

  92. Daniel Flynn says:

    So I stood by as a bystander while the bottom end was replaced and now it seems like its stuck in gear. What did he miss?

  93. Jackofalltrades masterofdanger says:

    thank you your video was really helpful

  94. Jamie Metevier says:

    I have a question….2008 crf450..doing this exact rebuild. But I dont know what direction the seals go. Paint on inside of seal go on the outside?. Or facing inward towards cranks. Btw they are all balls seals and bearings…

  95. Lewis Cross says:

    8mins hahaha look at those trousers

  96. Yee Thirty says:

    Hotrods does not offer a crank assembly for the early RM, DS or JR series bikes (same engine) as a matter of fact if you get one of these bikes be prepared to search your ass off for rebuild parts and custom ordering some bearings and seals from an INA/FAG or SKF dealer.

  97. andrew davis says:

    Is a machine shop an absolute requirement when rebuilding a crankshaft and if so is the case for all engines?

  98. bugsysiegals says:

    The crank bearing seized my KX250F, which also damaged the sleeve/piston, and I've tore everything down for rebuild. I've removed the main bearings and also some of the others shown here which you've not removed. There are a few I'm not sure how to remove but am wondering why you didn't remove them, is it unnecessary or are you just demonstrating how to replace the crank bearing?

  99. gordon mazy says:

    Is there any way to diagnose a possible bad crankshaft main bearing seal?
    I've got a 05 ninja 250 with just under 4700mi, the seal shouldn't be bad but I've got a lot of oil/fuel mix coming out my exahust.
    Prior to this leak the bike sat for about 3yrs then was briefly ridden, the old fuel drained, carbs cleaned and reset to factory specs, no additional or after market parts have been added. New oil and oil filter, cleaned the air box and air filter.
    The bike runs but has not been ridden or run much since the work has been done, the RPM's fluctuate at most 500rpm's and have a difficult time staying between the factory 1300-1500RPM's at idle but won't die unless the RPM's drop below 1000RPM's so I guess you could say it's running strong considering.
    The proper oil quantity (1.6qt)was added after a warm drain and shifting through the gears, but the bew oil didn't show up in the oil peekhole for a bit which had me slightly concerned even after shifting through the gears post oil change.
    Obviously if the bearing seal is out, it will cost more money to have that work done, or more time then is worth the cost of the bike to repair.
    Is a cylinder pressure test or oil suction test the only method to checking if this seal is out? Or are there any other non-intrusive methods for diagnosing a bad seal?

  100. Christopher Maloney says:

    How similar is this to taking apart a 2005 DR650SE? I believe I need to replace my crankshaft connecting rod bearing, I have never worked on a motorcycle engine this involved before

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