Motorcycle Bottom End Rebuild | Part 3 of 3: Final Assembly

Everything You Need To Rebuild Your Bottom End!
www.rockymount...
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 @ www.rockymountainatvmc.com!
Click Here For Part 1 (Flywheel, Stator & Clutch Removal)
• Motorcycle Bottom End ...
Click Here For Part 2 (Splitting Cases, Crank & Transmission Removal, Crank & Bearing Installation)
• Motorcycle Bottom End ...
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/ @rmatvmc

[@rmatvmc]

Experience the ultimate convenience to get all the correct tools, and parts you need in order to get your OHV back on the trails. www.rockymountainatvmc.com/Sales/1974/Bottom-End-Rebuild?Bottomeendrebuildpart2&

[@poogocker]

I watched this video about 6 months ago when I bought a bike with a blown bottom end. Decided to give it a try and my bike is still running strong. I even bought the fancy tools you got to. I now do work on my friends bikes as well. Thanks!

[@zachsylvestermotocross48]

all of you guys at rocky mountain deserve a pat on the back your service is the shit and it's awesome how you guys put things out like this and reply to any questions it shows you care about your customers and enjoy riding and fixing bikes as much as we do! keep up the good work you'l always be my main source for product/service!

[@rmatvmc]

Thanks zach sylvester! We appreciate the feedback and yes, we do love to ride!

[@andrewacton5885]

ive referenced this video for rebuilding motors numerous times over the years. it doesnt get any better than this

[@jonsmith3723]

I appreciate all the information that you are giving me. I need it all.

[@carsonvandegriffe3764]

This video has been a lifesaver. Without it, I don't think I would have been able to tackle the rebuild on my '06 yz250f. God bless!

[@rmatvmc]

That's so good to hear! Glad we could help with your rebuild!

[@nvader88]

I too appreciate the fact that you put these videos on youtube. Even more that you do respond to questions and comments. guys like me spend more time trying to keep my kids bikes going than riding my own, and businesses/people like you help guys like me a lot! I purchase a lot from RM ATV and will continue! Thank you!

[@rmatvmc]

nvader88 Thanks a bunch! Maintenance on a family of bikes can be a full time job in itself! Let me know if there's any videos that could help you in the future and thanks for watching!

[@happyg.444]

I just wanted to let you know that I tore the 99yz250 completely down and all I found was a loose shift drum bolt. I went ahead and put new crank and all in it and new top end.I just fired it up! It started on the 3rd kick! I can't thank you enough for the videos!! I am so proud of myself! lol Thanks a bunch!

[@GatheringSticks]

best instructional video on this subject on the web.

[@amarcosdurock2009]

This video will be a great complement to my English classes. Thank you.

[@mickeysaathoff938]

I can't say how awesome it was to watch your instructional vid's. I am taking a course at home that does not include the videos and these were a huge amount of help. Thanks again.

[@dblock2626]

Once I got clutch and bottom end connect to bike its shifts smooth, thanks a lot to every at rockymountainatvmc u guys have been more then helpful

[@factoryXperimental]

Putting the transmission back in, yeah. Totally pro removal and installation in the video. Awesome!

[@ronaldcardwell3737]

Yup I accidentally dropped my shifter forks n got gears outa place They left out the hour it takes to get your shifter forks back on the shifting drum and in between the right gears

[@Kjames9951]

Wow man, just wanted to say thanks for taking the time to show everyone how to do that. I have built several top ends but never dreamed I would attempt the crank and berrings until I watched you 20 times. I ordered all the tusk tools you mentioned, a service manual, berrings, and a Hot Rods complete crank like you said. Very nice tools and crank by the way. Now, if I only had a bike to work on.... Just kidding. The tear-down is almost complete. Thank you for your videos.

[@rmatvmc]

having the right tools can be the difference between easy and nightmare.

[@checkurhead801]

Thats impressive i rebuilt the bottom end on my kawi and it was all but a f--king nightmare! you made it look pretty easy

[@rmatvmc]

Thanks and good luck. The heating does work on the kx if you heat it in an oven (200 degrees is all it takes and it won't hurt seals). The oven method does stink up the kitchen though!

[@rmatvmc]

The right tools definatly make a huge difference. good luck!

[@chonjio1]

You guys are AWESOME, I'm about to rebuilt my 2 stroke yz250. I am learning a lot from your videos. Thanks very much.

[@rmatvmc]

Sounds good, glad to hear it was just that and not something worse!

[@dizzyspud10]

you make it look so easy, I have never do this before but I might give it ago by following this video :/

[@rmatvmc]

it is hard to shift when the motor isn't running and you are trying to shift it by hand. However neutral should not be all the way down. Try spinning the countershaft with one hand while trying to shift. This helps the gears move into place.

[@bahamaboy25]

i am satisfied with you rockyMountain ATVMC guys

[@rmatvmc]

This video should give you a good start. There is simply not enough demand for that specific bike but it will be similar enough to this video and if you follow a service manual you should be able to get the job done.

[@CptBigLips]

that is some good shit. i can definitely see this coming in handy later. tusk sold me, ill buy their stuff when i do it too. great video. 5 stars.

[@rmatvmc]

WOW! 1893! i didn't know Suzuki existed 116 years ago. Assuming it is 100 years newer, i would recomend Belray, Maxima, etc, motorcycle 80 weight gear oil.

[@rmatvmc]

You can find this on our website, the part # is 117380002 and it's the Tusk Crank Puller/ Installer Tool. Click on the link in the video description and search the part #.

[@ivanbogdantsev5607]

Are you using Tusk camera ?

[@mxracer711]

LOL bro that made me laugh out loud for real

[@tylerjames3526]

13th Apostle I peed a little when I read this 😂

[@rmatvmc]

Most likely will need to have someone repress and ballance the crank. The right tools make all the difference. The crank must be pulled into the cases, it can't be forced.

[@rmatvmc]

- yes it is. the gears need to be moving so they can slide into place. It is difficult to spin it fast enough by hand sometimes (Which always makes you nervous when rebuilding)

[@rmatvmc]

You have to be able to pull the crank into the bearings. If you push it or force it somehow from the opposite side you will most likely damage the crank or throw it off ballance.

[@rmatvmc]

This is the same problem with most Kawaskis. The best thing to do is assemble the engine (crank and transmission) in the right crank half first, then pull the crank throgh the left side for final assembly. This way you can heatthe bearings in the right side and freeze the crank so the crank drops into the right side.

[@emanonup]

Rocky Mtn.you have the best how to videos out there thanks!

[@Enduron1Gerry]

This video is one of the best I've seen. I look forward to more of your mechanical illustrations. I race enduros and have 03 and 06 KTMs (EXC and XCW). This video will be useful.

[@rchrd1bolt]

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 ,

[@rmatvmc]

@brentnowell - 1 - The crank goes all the way in. 2 - We don't change the timing. We put it back where it originally was, which is where the manual recomended. 3 - we don't need to check the timing after the piston was on. we set the stator to where the manual said to set it. 4 - I wouldn't say bearing wear in the transmission is common - it depends on how bad the wear is. 5 - the bar stock comes with the tool. steel.

[@rmatvmc]

There is really only one way it can go. Refer to your service manual to make sure you got it right. It is worth noting that it is difficult to shift it whil it is on your work bench. You need to spin the drive shaft quickly while trying to turn the shift cam to get it to shift. Turning the drive shaft gets the gears moving and keeps them from binding up.

[@rmatvmc]

Sweet! Glad to hear that's all it was and that the videos helped you out. Good Job!

[@redrider37j]

Ok, thanks a lot. The bike is a 2001 cr125. I'll definitely be referring to your videos during the tear down.

[@rmatvmc]

- that was kind of the point of this video. the tools we use are the tools you need.

[@rmatvmc]

I don't have the manual either. I recomend getting one to be sure.

[@TheYamaha109]

Saved me 1000 thank you so so soo much

[@rmatvmc]

If there was a gasket there then you need a gasket. The tolerances of the case halves are designed to have that gasket in there.

[@rmatvmc]

Refer to the manual or parts diagram. It is usually quite simple. you need to pull the spring back so ther is tension on the spring. It should just slide in.

[@rmatvmc]

It fits most. There are a few that it won't work on. I am not certain what tool you are refering to though. Case splitter works on all, crank puller won't fit the raptor 660 and a couple others.

[@rmatvmc]

@sx512 - you can split the case from the other side, but if you want to remove the transmission from the case you need to take out the stuff on the right side.

[@rmatvmc]

It depends on the problem. If the bottom end has a bad crank or crank bearing (or is showing wear), you need to rebuild it. Of course if you have a transmission problem, you need to split the cases as well. However; if you don't need to do it, then I wouldn't do it for no reason.

[@rmatvmc]

you have to split the case to change the bearings. When you split the case you have to deal with the transmission. Yes you need to remove it. It isn't bad though. You will do fine.

[@rmatvmc]

Your main bearings would be affected by whether your clutch is pulled in or not. When the clutch is pulled in gears in your transmission stop spinning (even in neutral). Most bikes make a little more noise (in neutral) when the clutch in engaged as aposed to being disengaged (pulled in). That is because you are driving gears in the transmission. You may just be hearing the gears driving each other, or you may have a bad clutch basket bearing or some other shaft bearing.

[@happyg.444]

Oh... I just ordered a torque wrench! Hopefully this will save me in the future! The right tools for the job makes it a whole lot easier!

[@rmatvmc]

You should be able to shift through the gears without having the clutch assembly installed. Some bikes will be smoother than others and a little oil will help the gears shift but yeah you should be able to shift through without the clutch assembly installed

[@rmatvmc]

if your center case halves require a gasket then you need to run the gasket. The thickness of the gasket is critical if it is made for it.

[@rmatvmc]

An expert had to start as a novice at some point. With the right tools and a service manual to double check your work, you will be a pro in no time!

[@rmatvmc]

Some symptoms are you'll have knocking or noise coming from the motor. Sometimes it will cause a whine or whistle almost if your bearings is spinning in the case.

[@tylerw2239]

this makes me confident that i may be able to do it myself. The transmission assembly looks scary I would hate that thing to fall on the ground in 400 pieces.

[@rmatvmc]

it depends on the bike for the "absolute needs", but you can do most with theses "must haves". flywheel puller, case splitter, crank puller, and snap ring pliers. And of course your common tools. It realy isn't that hard. Just takes a little time.

[@rmatvmc]

@troyfrtc - the joys of electrical problems! it could be a lot of things. I would suggest having a shop diagnose the problem.

[@rmatvmc]

Not necessarily. Only if the crank spun in the main bearings. The biggest reason to change a crank shaft assembly is if the lower rod bearing wears out. It is usually cheaper to replace the whole crank than to buy the rod assembly and pay to have someone press it in and balance the old crank.

[@rmatvmc]

On a rebuild, we are not refering to power; rather, the area of the motor. Top-end usually refers to everything above the crank. Bottom-end refers to the crank.

[@rmatvmc]

What all did "fixed it from leaking oil" entail? If it shifted through all the gears before the "fix" something may have been done when you were working on it but i'm not exactly sure what you did...

[@rmatvmc]

If your crank is moving then you have problems. Your rod will usually be able to move side to side a little, but it should not be able to move directly up and down. The crank should not be able to either. Grab the flywheel to test for any free play in the main bearings. It should be solid.

[@rmatvmc]

it should only have one screw that adjusts jetting - the air screw (The other may be an idle screw) the air screw is a minor adjustment on the air/fuel mixture on the slow jet. it should be set between 1 to 2 turns out. 2 being the leanest. If you are still rich on the idle to 1/4 turn, then you need to go with a smaller pilot jet. The only way to lean the needle is by either changing it or adjusting the clip 9raise clip to lean) to adjust main jet - it must be changed.

[@rmatvmc]

i think it is possible. I suggest trying again with a gasket.

[@rmatvmc]

you could, but i doubt you will find the problem that way. you need to take it apart, put in the gasket that is needed, and carefully reassemble.

[@sammig330]

Thank you very much for the video. couldnt of done it without it

[@yamahass125]

Thank you for your inputs. The oil looks black and muddy during change. I am planning to open the magneto cover and check everything up. thanks again. If i find something ... will update you.

[@rmatvmc]

Great question. No it won't. Most KX cranks have a c-clip holding the primary gear on the right side of the crank, so the tool doesn't have any thing to thread into. The best think to do on the KX is to heat the bearing a little, freeze the crank, then install the right side of the crank first. Then instal the tranny on the right side. Then use the puller to pull the left case onto the left side of the crank for final assembly.

[@rmatvmc]

It doesn't look like they have changed the Main Shaft or the Countershaft since 99 but i would recommend checking the OE numbers after you have torn it down and figured out exactly what is wrong and then going from there. They may be the exact same parts from 99 up so it may not matter. Thanks!

[@rmatvmc]

Yeah it sounds like you've got a bent shift fork shaft or one or more of the shift forks could be screwed up. The channels in your shift drum could also be either worn out or chipped off. Have you changed the oil in this bike yet?

[@rmatvmc]

@dmbnorthphilly - check out our website for tool and part pricing. If the main bearing is stuck in the case, you either need to press it out or carefully pound it out.

[@rmatvmc]

- you could seperate the crank from the transmission by removing the clutch. As far as free-play goes, you should have none when grabbing the flywheel. If you do, you have wore bearings.

[@rmatvmc]

yes we do. refer to our website.

[@rmatvmc]

@tlbohanon - The last thing you want to do is press it in. it has to be pulled in. On a KX250 you need to heat the case half in an oven (flame eill damage internal seal) and freeze the crank. It will drop right into place.

[@rmatvmc]

It's obviously going to depend on the bike and how smoothly everything goes. If you had all the parts and correct tools you could do this in a day

[@socrati007]

nice vids makes everything look easy (with the right tools of course) and congrats to you for explaining everything

[@eamh2002]

I put my crank in the freezer, it dropped in the bearings like butter :) No need for force.

[@rmatvmc]

@79stingman - Yeah, I would have done more to diagnose the problem before. Do you know it was a problem in the transmission? Could the cylinder or crank have been full of gas from being laid down, locking the piston? I have never seen a shift fork jump out of the drum. if it did, you would see some seriously bent forks and most likely some ground gears (a wreck won't do it though). I am not sure what to tell you without knowing the problem. good luck!

[@rmatvmc]

It's hard to say what it is because it could be quite a few different things. Can you tell which side of the motor it's coming from? You might take your magneto cover off and make sure everything is tight in there. How does your oil look when you change it? That could give you a good idea as to what could be going on...

[@rmatvmc]

whatch close. Our clutch cable is hooked up when the cover goes back on.

[@rmatvmc]

@crf250rider6 - if you want to do it right - YES. it takes a few hours with practice.

[@rmatvmc]

I always recomend you follow your manual. I use normal Bel-Ray bearing grease. The purpose of the grease is to make sure the seal goes on right, and to make sure the seal breaks in right.

[@rmatvmc]

Glad we could help!

[@happyg.444]

Well... I'm not sure the right side crank bolt had worked loose.(I used medium strength lock-tight on all the bolts) When I tore it down it had a broken clutch spring bolt,my fault, I didn.t have a torque wrench,then I noticed the broken clutch rod. Plus the clutch actuator arm had a chip in it,so I order more new parts, hopefully this will cure the problem.I tried to save some money by buying an older bike, but it is nickel diming me to death now. Thanks for all your help! You guys are GREAT!

[@suponcozaabuild1400]

I will repairing my bikes thanks for guide video.

[@rmatvmc]

suponCoZaA Build You're welcome. Thanks for choosing Rocky Mountain ATV/MC.

[@wardy1231980]

hey man, great vid. Im changing my 1st gear cog and shift fork on my yz250 2000 model. this vid is such a great help, thanks.

[@rmatvmc]

@paintballer2X5 - i assume it is on a stand with the tire off the ground??? This is most likely normal. There is still drag in the transmission that will move the wheels some when off the ground. It it wants to drive off on you, you may have a problem.

[@rmatvmc]

Yes. you have to pull the cover off, remove the clutch basket and primary gear. The seal is in there tight!

[@topstar3]

Thanks alot. I just watched the bearing removal video, and I'll be ordering a Tusk Bearing Removal kit this week from RMATV. On another note, keep up the great work with all of your videos. I enjoy watching them all.

[@rmatvmc]

@stutest2 - i am not sure. I would use what the manual recomends. In this case it was yamabond 5.

[@jeffpallaro6952]

Thank you guys for using a yami for the demonstration.

[@rmatvmc]

You need to know how to do this if your main or lower rod bearing wears out. Or if you have to fix anything in the transmission.

[@rmatvmc]

Garret Blackburn - The difference in liquid gasket makers such as Yamabond and a "Regular" Liquid gasket maker is the recommended gasket makers "as stated in your service manual" are designed to hold up in a higher vibration higher heat situations so that's why you always want to follow right along with what your service manual is saying

[@baggie00001]

Use Loctite 5920 Premium copper gasket sealant. Its better than Yamabond and is a fraction of the price. I get mine from Halfords.

[@peterpalamaris2730]

Rocky Mountain

[@dr00andrew]

@@baggie00001 good for you!

[@dimitriostsesmetzissr8845]

You make look way to easy I rebuilt 3 of my motors and every time i forget where all the parts go to hahahaha .... Nice video though ...

[@rmatvmc]

@83BigChevy - What altitude are you at? Why do you suspect it isn't rich? Suposing it isn't, you could have a right crank seal leak. That would draw extra oil in from the transmission.

[@rmatvmc]

@dmbnorthphilly - Did the crank spin smoothly when you got the cases together? I hope you used a crank puller. Retrace your steps and see what is rubbing or hitting. It could just be something with the kick start mechanism.

[@rmatvmc]

@KX817 - Great question. If you have a KX with the c-clip that holds the primary gear on, I now have an adaptor that works with our crank puller. It should be in stock this week!

[@Nym1a]

"sweating" in the bearings into the case, as well as sweating in the crank into the bearings is way better than to use some wierd special tools wich maybe wont place everything correct. IN MY OPINION! :) (cheaper too)

[@Krispii347680]

Hampus Olsson what do u mean ‘sweating’?

[@ReaperAHHH]

heat the case freeze the bearings/crank

[@rmatvmc]

did you use the right tools or did you force the crank in and out? That will lock it up.

[@rmatvmc]

@Sandeep9201 - you most likely have a bad shift fork and a couple gears. you will have to split it to inspect. i am not sure about the cam mechanism you are talking about without looking it.

[@denzlepob]

Another superb instructional video, well done.