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

Motorcycle Bottom End Rebuild:
www.rockymount...
In this 3 part video, we'll be demonstrating how to completely rebuild the bottom end on a modern day 2 stroke motorcycle or ATV engine. Installing a new crankshaft assembly and crank bearings is all part of this process and using the right tools is going to make this process quick and easy. This is part 1 of this 3 part engine rebuild series from Rocky Mountain ATV/MC. In this video we cover the beginning engine tear down such as removing the flywheel and stator assembly. We'll also be removing the clutch assembly and the right side engine cover.
Watch Next:
Motorcycle Bottom End Rebuild | Part 2: Crank & Bearings
• Motorcycle Bottom End ...
Motorcycle Bottom End Rebuild | Part 3: Final Assembly
• Motorcycle Bottom End ...
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[@rmatvmc]

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

[@jacobcragen7133]

Thanks guys - I was really dreading this...Bought a used '98 wr (was the only one for sale with a title) and guy did new cams+chain.....but 2nd ride the piston seized to the crank....so I pull the bottom end and there's tons of stuff going on in there...This video series, and your entire channel/company/business, makes me feel comfortable DIY'ing. Happy, even. Ain't nothing like wrenching - Just the money what's an inconvenience.

[@rmatvmc]

@RicNetro17 - thanks! Glad you like them.

[@rmatvmc]

- the big c-clip is for the kx250. For the 65, fit the black collar over the shaft and use the stock c-clip. I just tested the fitment here and it works great. If you are having problems, give me a call.

[@SirSmighty]

I acquired the tools shown in this video got my laptop and pulled this video up for backup then had my crank bearings in my ktm 250 2 stroker within a few hours. very helpful keep these videos coming!

[@rmatvmc]

Yes i would say these tools are mandatory tools. I guess it is possible to do it without them but these are going to save you a ton of headache and possible damaged or broken parts if you try to do the split without them. A very smart investment

[@jeffstone2601]

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

[@rmatvmc]

It is actually quite easy. I am sure anyone could handle it.

[@jackedsports4114]

Holy cow this video was made in 2008 and better quality than most all videos made now on these subjects

[@enoxosr1]

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

[@rmatvmc]

The puller is only used to remove the flywheel. The flywheelgoes on simply by tightening the nut or bolt. Once it is tight, you need a puller to get it back off. Because of the shape of the puller and shaft, the puller will stick.

[@LotLizardDiesel]

Really appreciate the channel! It has given my close friends and I the drive to make our own KZbin Content! Thanks so much!

[@cr250FoLife]

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!

[@rmatvmc]

Stephen Svetz Good to hear man! Thanks for watching.

[@amarcosdurock2009]

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

[@rmatvmc]

i suggest pulling the magneto to eliminate that factor as well.

[@rmatvmc]

It is hard to say. Unless you have unhooked your primary gear on the right side your crank is still driving the clutch and water pump. It could be resistance from those as well. remove the primary gear on the right side of the crank to be sure.

[@rmatvmc]

That is an 8mm T-Handle but we offer these in all sorts of sizes along with different types and sizes of screwdrivers. If you go to our site and type in T Handle it should pull up everything we offer.

[@rmatvmc]

It depends where the break is. if it is the right side of the center case, you are better off just taking apart the left and right sides. There isn't much on the left side anyway. All the hard stuff is on the right and you need to do that anyway.

[@rmatvmc]

Thank you! About the crank bearings it's hard to say if that is what's causing the whining noise or not. Those symptoms are hard to diagnose but if possible try and figure out where exactly the noise is coming from. Change your oil and see if you notice anything out of the ordinary. Also check your stator and make sure nothing is loose in there. As for your other question no dry ice is not required. You can just stick the bearings in your freezer overnight and that will be sufficient.

[@rmatvmc]

A very important question indeed. No doubt your head gasket is shot; however, it shouldn't cause the water in your transmission. I think you have a leak somwhere else. I would check the water pump seal.

[@rmatvmc]

Thanks. We appreciate your business. We will get more videos coming.

[@rmatvmc]

@rockmusicismyidol - Kawis are tricky because they don't have a bolt or nut on the right side, making it hard to use a crank puller. The best way to do a KX, or KDX is to heat the right case half in an oven to about 200 F (this is about where water boils and it won't damage your seals). Freeze the crank. Once the crank is froze and the case (and main bearing in the case) is hot, the crank will drop right in. Assemble the transmission on the right. then use a pulling to install the left side

[@marconi1982]

Freezing the bearing slightly shrinks the metal and heating up the case slightly expants the material. It makes it easier to get the bearing in. Same with wheel bearing on cars etc.

[@rmatvmc]

You will need a case splitter to get the case apart easily without damaging anything. The crank puller is critical to prevent stress on the crank. The crank must be pulled (not pushed!) into the case halves so you do not knock it off balance or cause other damage. I highly recommend the right tools for any job.

[@rmatvmc]

@Krazer2100 - take your time and pay attention to how each part comes off. It is fairly easy. One step at a time. I do recommend a service manual if you can find one. The manufacture should have one.

[@rmatvmc]

It is probably fine. Be careful not to break the hub. They are fragile. Are you rebuilding the crank?

[@rmatvmc]

There's a number of different ways to get your case apart and you'll find some other videos here on you tube but using the case splitter tool is by far the smartest and most reliable low risk way to get your cases split.

[@rmatvmc]

I am not sure what you mean, but if it is in neutral and the transmission binds when yu push the bike, it sounds like you have some serious problems with eithes some transmission gears of shift forks. You may want to disassemble and inspect.

[@rmatvmc]

@OPureGHOST - they are both very different. You can hold a flywheel with the clutch holder tool, but it won't remove the flywheel - you need both tools working together. On the clutch, the flywheel puller won't do you any good.

[@bubster1981]

To maximize outer clucth hub life i always mark the pack ...with a simple scribe mark along a series of plate tabs...and a identifying mark on the basket. ive noticed if the plates r put back in any order sometimes the tabs wont mate proberly to the basket...which in turn causes un needed wear until they bed back in

[@carpetinbathroom]

Excellent stuff.

[@rmatvmc]

Sounds like you could have bent shifting forks. Most likely the cogs on some of the gears are bad too. When one or both of these problems occur the transmission will fall out of gear.

[@rmatvmc]

It's bound up somewhere but it could be in a number of different places. You may have to end up splitting the cases to figure out what it causing it to seize up but it could be something with your crank or a gear or something with the transmission or possibly something else so I would refer to your service manual for further suggestions

[@rmatvmc]

it depends on the bike. I think this one was around a 27-30mm.

[@rmatvmc]

@ChiefDrakula - many bikes will get hot and spit a little out. If it is getting below the cores in the radiator you may have a bad cap or a bad head gasket that is pressurizing the cooling system. If the bike is OK, we sell a Tusk high-pressure cap that works great.

[@CptBigLips]

oh yeah, and the flywheel puller too. thanks.

[@rmatvmc]

I haven't heard that the tool won't fit a KX100 until now, but I could see the splines being too small. I am not sure. I don't know what you mean when you say you "hogged the slines". You can use an impact. I wouldn't use it to put it back on, but coming off should be no problem.

[@rmatvmc]

Good call. The cam(little gear) can be checked by removing the right case cover. Do that before splitting the case.

[@rmatvmc]

you need to find the correct flywheel puller that your manual calls for do do it right. You don't want to ruin your electrical componants or crank by doing it wrong.

[@rmatvmc]

@BigManlyMan4 - great question. Two ways to do it. 1. wait for the snap ring adaptor we are going to stock - I have one in production now that is specific for the KX250. It won't be done until mid september. 2. heat the right case half to 200 degrees in an oven (flame will ruin the seal). Freeze the crank shaft. It will drop right into the warm crank bearing. Then assemble the tranny on the right side. Use the tool to pull the left side together.

[@rmatvmc]

It could be a few things. 1 - leaky right crank seal. 2 - too much premix in gas or injector is dumping too much in (if you have an injector) 3 - poor jetting - very rich fuel mixture. All 2-strokes smoke some what. Keep a close eye on the color of your spark plug.

[@rmatvmc]

I'm not sure what you mean by "beside" but you've got your left crankcase cover on that side and you've also got your clutch actuator cover which sits right behind the left crankcase cover and right in front of your front sprocket and both of those have gaskets under them. Or are your referring to the seal or o-ring that sits under your front sprocket?

[@rmatvmc]

It depends on what bike you have and you may have to refer to your service manual but some bike use a bolt with a retainer or a snap ring that sits down in that channel or a bolt that sits in a channel on the actuator arm. Others will pull out once the push or lifter rod has been removed . . .

[@rmatvmc]

@bailycoco - your premix at 40:1 is fine. If it is oily it can come from only two places. 1- oil in gas. Since your ration is fine I would check your jetting. 2. transmission oil. This can leak into the crank from a bad right crank seal. You may want to check your pipe as well. I have seen many bikes (especially 125 and smaller) plug up with carbon and oil in the narrow part before the silencer (and in the silencer). Make sure that is clean and clear.

[@rmatvmc]

@LVRidaZ - The right case cover will come off, but the two center cases won't come off until you remove the cylinder and pull the motor from the frame.

[@cr250FoLife]

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

[@rmatvmc]

Stephen Svetz Being a "bolt style" that threads in to hold the gear on i doubt it would be a left handed thread. I just looked at the microfiche for your machine. Lock the clutch up with a nickel or penny and hit it with an impact gun, should break free.

[@rmatvmc]

side to side is most likely normal. up and down movement means the bearings are shot.

[@rmatvmc]

It depends on what problem they are fixing and what the shop rate is. You can easily exeed 500 bucks on the labor though. rocker arms can wear, but I wouldn't consider them 'high wear" items.

[@rmatvmc]

I doubt it would come loose, but it could definitely wear out and leak.

[@rmatvmc]

@BigManlyMan4 - Yes, you will need it tp pull the crank into the bearing.

[@rmatvmc]

The tool shown at 1:06 is our Tusk Clutch Holding Tool - Part # (1188510001) and the tool shown at 7:25 in the video is our Tusk Crankcase Splitter/Separator - Part # (1177390001).

[@rmatvmc]

- if compression is low or you sucked some dirt or sand. Or, when your manual says it is time.

[@rmatvmc]

- it really depends on the person and the bike. they are all different.

[@rmatvmc]

- did you buy the C-clip adaptor tool for the KX 65 (part #1329270001)? You need that to attach the tool to the right side of the crank.

[@rmatvmc]

Yes it should be a 27mm Puller for your 99. I checked our apps and for some reason we aren't listing this for the bikes prior to 2000. I check the part numbers on the OE schematics and they superceeded to the newer flywheel for 1999 so the 27mm puller for the 2000 should work. We will get the apps updated asap.

[@rmatvmc]

You should be fine reusing that lock washer when reinstalling the clutch assembly

[@dreadlock8275]

Hey can I get some help plz idk if you still use this chanel or even are alive but I was riding my birthers bike and I think I blew the clutch not sure I keep looking for videos to show me what I broke but I can't find any plz can u reaply asap

[@rmatvmc]

@rickyelementsk8er - It makes sense, but the only way to know is by pulling it apart. I would be concerned about the oil pump if this is the case.

[@rmatvmc]

sure they can be applied.

[@rmatvmc]

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

[@braydendenlinger9428]

Very helpful vids.

[@mozer30]

Certain types of billet clutch baskets are heavier than stock cast,i know some Hinsons are.However billet has no casting floors so are meant to be stronger.Most are hard anodised as well to make them last longer....What you have to think about is if you do get a lighter basket then yes it will give better throttle response but you will loose torque as there is less rotating mass within the engine

[@rmatvmc]

Part # 1179010002 will fit both bikes and most other two-strokes. You don't need any special tool to put it on. just tighten the nut.

[@rmatvmc]

@memphetic - if you actually have a penny made of 100% copper (made from 1793 to 1857), I wouldn't ruin it. It is most likely worth a lot more than 1 cent. If you have a penny older than 1982 it will most likely have a decent ammount of copper in it. 1982 and newer are 97.5% Zinc with copper plating. The aluminum washer works great!

[@rmatvmc]

It's just going to depend on what is causing the leak; if for some reason your right case cover has a hole or a crack in it you may be able to fix it with some JB Weld or something like that. If it's a tear in the gasket simply replace the gasket but sometimes if you've got a scratch in the sealing surface a little silicone will help it seal. Go ahead and remove the case cover and that should tell you pretty quick what is causing the leak

[@RCGIGSportugal]

your videos are very good but what I really needed was a video of yours if it were possible to repair a motor dt 50 lc. if it were possible .. very grateful ... good repairs

[@lotsofspareparts]

I have found (after many bottom end rebuilds) that instead of a hand held impact screwdriver, the better tool to use is a Craftsman Impact Driver. They are 19.2 volt cordless, and it has a quick connect bit attachment. I am a Sea-Doo mechanic (and do pretty much any 2 stroke wrenching on the side) and have found it to be invaluable.

[@rmatvmc]

Most likely the bolt and the pivot bearing bushings are rusted together. This makes getting the pivot bolt out very difficult. Spray as much "liquid wrench" or equivalent spray on the bolt as you can. Then, try pounding it out. Put something on the end of the bolt so you don't damage it. If it won't come, you need to find someone with a big press. Good luck!

[@rmatvmc]

@Bajabugman23 - I guess it depends why it won't come off. What is keeping it from coming off? Where are you having trouble?

[@rmatvmc]

@bikercc - i think we show that in the video. Do you have a clutch hub holder tool. if that won't do it, use a pneumatic air impact.

[@rmatvmc]

The process is about the same for any bike. We used a YZ250 in this video.

[@rmatvmc]

No you shouldn't need to do anything with the clutch. It's just the cover that needs removed so to do that your kickstarter would need to be removed but that should be about it. You shouldn't even need to remove the clutch cover, just the right crankcase cover.

[@eskimoto4417]

I liked the video; enjoyed it. Liked and subbed, great content !

[@rmatvmc]

Awesome! Thanks for checking out our videos!

[@rmatvmc]

@troy118 - I would worry about it. I would start by removing the right case cover to look at the shifting mechanism. Maybe you will see the problem there. If not, it may be in the transmission.

[@MultiBamf69]

Well. It could be the transmission dog that grabs the 3rd gear..Or a shift fork is bent. Or the shift drum is to worn out..Im pretty sure the problem will cause you to split the case. Unless a rod somewhere bent or ceased. hope this helps you.

[@rmatvmc]

The flywheel pullers will usually always be specific to your bike. They do make universal pullers but we don't carry them. As far as other bottom end tools we have a case splitter (1177390001) and then we also carry a crank puller/ insttaller tool (1177380002) and then a clutch holding tool (1188510001) as well which are all universal tools.

[@rmatvmc]

Sometimes it can be hung up by the actuator arm... try and rotate that a little and see if that allows you to pull the rod

[@rmatvmc]

With philips head screws - using and impact driver prevents damaging the heads.

[@rmatvmc]

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.

[@archiveprivate]

Thanks That exactly what I was thinking, Is there an easy way of checking the waterpumps seal for leaks? Its hard to tell by just looking at it. It looks fine but I know that dont mean it isnt leaking. Thanks for your time i really appreciate it.

[@rmatvmc]

@jacquestdi - this is a YZ250. You need the 27mm puller for your YZ125 (same as the 250 and most other 2-strokes). good luck.

[@wolfgang29]

it makes the front tire fly up in the air its like the powerband thats why they say 2 strokes r easy to catwalk

[@rmatvmc]

@vinnyvalenz - thanks for your comments. Sorry, but we aren't hiring now. Good luck with your new career choice!

[@mikeyforester6221]

great video very helpful thanks

[@rmatvmc]

Yes you can!

[@rmatvmc]

I can't imagine it would. i guess it depends on what the scratch was damaging. Just on the steel? i don't think so.

[@rmatvmc]

@surlybonds71 - yes. you will have to pull the right case cover off, remove the clutch basket and then slide the shaft out. replace the seal before putting the new shaft in.

[@rmatvmc]

2004 YZ250. not every machine will be exactly the same. Most the steps in this video are close to most modern engines out there. Refer to your service manual for your specifics.

[@rmatvmc]

@15tbizzle - It you can't work it out, you will need to drill the bolt carefully (centered) and use and easy-out bolt remover.

[@GuitarMan96]

Cool, thanks

[@rmatvmc]

@Yamahayz2502t - go to our site, enter your machine, and do a keyword search for "puller". You need a 27mm puller.

[@rmatvmc]

@bairdybee - you need a manual and you need to see how the shaft links up to the shift cam. Something isn't hooked up right.

[@rmatvmc]

I supose it depends on the shop. You will get your best estimation by calling a few in your area.

[@rmatvmc]

I would change the water pump seal. That is the most liekly problem.

[@dadygee]

youtube "show how" vids are such a lie.. it is never this easy. :) thanks for showing this!

[@rmatvmc]

@JoelPotter1 - the flywheel is "wedged" onto the crankshaft. It takes a bit of force to pop it loose.

[@rmatvmc]

@heparsons - It isn't actually an "overflow" hose. it is just a breather hose. some will drip out every once in a while. If it is losing a lot, I would suspect way too much oil in there.

[@rmatvmc]

- yes you will.

[@rmatvmc]

@Monsterenergy8771 - If you use a shifter that is loose, the splines end up wearing our quickly. The aluminum shift lever should wear out quicker than the steel shaft (assuming yours is aluminum). Inspect closely and replace what you need to. Make sure to watch the lever and keep it tight!

[@rmatvmc]

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...

[@olehoiii]

I am not looking forward to this.

[@joet6990]

so how did it turn out? lol, i'm about to order my tools and tear apart a 2 stroke for the first time.

[@TypicalJacques]

joe t same

[@goinhot9133]

joe t ah, I think I’m gonna be doing this soon too... almost wanna buy either a good camera to film it along with marking and organizing as I go, or, buying a junk motor and trying it first lol...

[@1MACVSOG1]

t did you do yours yet? How did it go?

[@1MACVSOG1]

@@goinhot9133 did you do yours yet? How did it go?