Case Splitting newbie

[Speeed]

Case Splitting newbie (pro's advice needed)

I am considering splitting the case on my 2000 YZ125 for a rebuild
my questions are :

1) is it worth it ? (bike has well over 50hrs of fairly hard riding on it)
2) whats the DIY expense?
3) whats involved and how complicated is it?

I have never split a case before but I am by no means mechanically challenged.
I want to do it myself mainly cause I dont have the money to pay someone to do it an being an inqiuzitive(sp?) mind I wanna know what goes on in there I just dont want to bite off more than I can chew and have my bike apart for months cause I screwed something up.
thanks

 

[blackoutyz125]

I have an 89 yz125 and I had to split the case replace my crank berings, it was a total pain in the ass. I did most of the work my self, but some things you need a mechanic to do unless you have all the specific tools. When the case was apart i replaced, all bearings, oils seals, connecting rod. Also you need to factor into the cost for crank truing and rebuild, complete gasket set and labor costs. Removed the motor, removed the top end/piston, took off the flywheel/ignition, clutch, kickstart gear, primary drive gear, external shift mechanism. Then I took the case to a repair shop and had them split the case and install the new bearings and oil seals, go through the tranny, and reassemble the case.

The reason I had a shop do this is:
1. Special tools are needed to split the case, and you can cause some serious damage by trying to do it the wrong way
2. You need a shop press to install bearings
3. I dont know jack sh!t about trannys so I figured to just leave that alone
4. You need more special tools to reassemble the case

The shop time for the case spliting, tranny work, bearing/oil seal instalation, con rod install, crank true,

 

[blackoutyz125]

Sorry my computer randomly restarted....

like i was saying, the final cost for the bottom end rebuild was about $450 for me. I all depends on what you wanna replace and what work you can or want to do your self. It was $450 well spent, it made my bike run :-)

 

[darringer]

Go for it. Your bike has alot of life left in it. Splitting the cases is not very hard. Also would be a great learning experience. Having the crank rebuilt is the biggest expense. The bearings are fairly cheap. Even cheaper if you can find the dimensions of the bearings and buy them from a bearing supply company. They are nothing special. The tranny is simple, also. When splitting the cases, the tranny will stay together in one case half. If you took good care of your bike, the tranny bearings are probably fine, but I would disassemble everything all at once to make sure. Your bike will be new again! Well, at least the motor!

 

[jackdrinker]

It's more taboo than anything... Take it slow and enjoy the learning process. The main thing is taking your time and making sure everything lines up...
If you weigh the cost of buying tools or having a shop do it, you'll end up like this:
Every time it needs to be done it will cost you $xxxx to have it done or:
Spend $xxxx on some pretty universal tools and do it over and over on every bike you have, for far less and the least amount of time..
Crank bearing do not have to be pressed in, a freezer and a heat lamp is all you need.

This is what I did:
Get a box of sandwich bags that seal
paint markers
digital camera
note book...
record everything and take pictures, label all bags in order.

My first complete rebuild took 7 strait days like eight hours a day..
Now I can do a complete in one day, from bike washing to final assembly..


Oh ya,
buy a gallon of simple green at the depot and a spray bottle.
wash the bike w/ a power washer top, sides and BOTTOM:
Then spray non-diluted simple green everywhere, let it sit for about 10min... scrub and remaining dirt and oil clods... hose off....

 

[Speeed]

Thanks guys! it doesnt sound to bad. I think I'll give it a try.
hopefully you wont see a "I cant fix my bike" thread :)

 

[darringer]

I had forgotten to mention the Ziploc bag trick. I used it for all of the "systems" on the bike. Like the clutch in one, the kickstarter assy. in another. Also if you remove the tranny, leave each shaft assembled with the gears and thrust washers. Hold them together with rubber bands, then each shaft into the Ziploc. Never tried the digital camera. They didn't exist when I did the first rebuilds. Use the manual for reference. The schematic pictures make it look alot worse than it really is. Just remember, if you get stuck, you have friends here that will help.

 

[Jim Clark]

The only special tool needed is a flywheel puller, 18.00$ at most decent shops or e b a y . Build a 2x4 box to cradle the motor when doing the work. Some large sockets and a small amount of mechanic skills is all thats needed. Don't set the crank seals too deep or you will block the oil gallery's. Might as well case match the cylinder/case while you have it apart, will help a little with the performance. Leak check before you attach the stator plate. There's a ton of info on the web concerning this.

 

[Speeed]

There's a ton of info on the web concerning this.

got any links?

I was lookin through the owners manual last night and the more and more I look the less afraid I am of it,
I mean I have assembled small block chevys from the pan to the carb, so I cant see this being to much more difficult
thanks for the help and the great tips.

if you get stuck, you have friends here that will help.

I may take you up on that :) thanks

 

[JasonWho]

You can look on www.ericgorr.com. He has an article on it.

 

[jackdrinker]

Pictures in the manual do no justice.... When you split the cases nothing will just fall out.. it's an assembly... everything comes out and goes in during stages...
I've built a boat load of turbo buick motors and they are not even comparable to an mx motor... so if you have done s/m chevy's pull up the skirt and get to it alice...

 

[SULLY]

My two penneth...in no particular order, and of the short rough and ready flavour...

If you have to hit anything use a rubber or at least copper faced hammer
Don't prize anything apart with a screwdrivers on mating surfaces
Use the heat /cool expansion properties of materials to aid removal and assembly
Always better to press than to drift...use the home vice with improvised blocks
Don't hit main bearings on the inner race
Be really carefull with new oil seals, lube them well and don't force them in at angles, it will damage them
Do a dry run assembly to ensure you have all the new parts you will need- don't be tempted to re use any bits you should be changing (like seals, circlips, bearings etc...)

I would say in addition to the specialist tools mentioned in other posts, you will need a clutch holder tool, and a crankcase seperator tool (you can make on of these search for the real thing on web for how it looks, then save a load by making your own)

good luck, it gets easier each time-! My last one took two evenings, which included time to check and order all bits needed for rebuild following tear down.

 

[oldgoat]

Don't forget the refrigrator for cold and the oven for heat, makes bearing installation easy.

 

[darringer]

Yep, I use a small toaster oven and heat one case at a time until water sprinkled on the case just dances off. Works like a charm, is dirt cheap, and keeps the wife off my back from using her oven. Put the bearings in the freezer for about 30-40 minutes to shrink them down. Then the bearings will drop in.

 

[Speeed]

ok so the crank bearings stay in there respective case halves? and can I trouble you guys for a list of must have specialty tools to do the job.
also like was mentioned in my original post, I have between 50 - 60 hours on it (maybe less) is a bottom end rebuild warranted or can it go longer. the bike is well taken care of, fresh premix every ride, tranny oil change every 3rd ride, air filter regularly serviced and the bike is never put away dirty.

thanks for all the help so far.

 

[darringer]

Before even splitting the cases, I would check the lower end for play. There should be no side-to-side play in the crank main bearings. After the top end is off, check the crank big end bearing. There should be zero play up and down in the big end bearing when the rod is pulled up and down. Side-to-side play is not that critcal, since it's a needle bearing. Maybe 2-3mm side-to-side clearance should be okay. If the cases need to be split, I have done it several times with just a flywheel puller for special tools. Instead of a clutch holder, I have used a penny wedged between the clutch gear and the primary gear to hold the clutch for removal. Torqued it back on the same way. Since the penny is soft, it won't hurt either gear. The manual is your best friend if you get stuck.

 

[SULLY]

On some bikes you can undo the centre clutch nut in the way you describe, on others you have to remove the pressure plate to access the nut, so using the penny in the gears method won't work as you have lost the grip between the plates. Depends on the model of bike though, I don't know YZ's

 

[Bodge]

I broke a tooth off an xr80's clutch gear w/ a penny. use a toothbrush.

 

[darringer]

Not true Sully, I think you misunderstand my method. After removing the plates, springs, and pressure plate, you can lock the clutch basket to the primary with a penny to remove the center bolt. The primary gear is what drives the clutch basket, so wedging a penny in between works perfectly. And it only costs two cents to r&r the basket!

 

[Pandaman]

The coin or tooth brush ( I prefer a copper washer) won't work on the YZ, it will however work to remove your primary drive gear (located on end of crank shaft.) you will definatly need a clutch hub holder, this can be made from a pair of vice grips. If this is too much trouble perhaps take it to your local workshop and have them remove it for you. A simple two leg puller with M6 legs is all that is required to split the cases once the flywheel is removed. To pull the crank back into the left crank case I use a piece of hollow 2" tube with a plate and 16mm nut welded to the end, a peice of all thread bar 16mm and an adaptor to screw onto the M8 thread to go to the M16 all thread rod. Do not hit the crank in with a hammer!! if this is impossible for you to make. Apart from that it is quite simple.
The only other trouble spot is removing the primary transmission neddle bearing, it is a very tight fit and will require a inside bearing puller, apart from that go for it!!

 

[Speeed]

To pull the crank back into the left crank case I use a piece of hollow 2" tube with a plate and 16mm nut welded to the end, a peice of all thread bar 16mm and an adaptor to screw onto the M8 thread to go to the M16 all thread rod.

Pandaman, is it possible for you to post a pic of this tool?
I can make it (I have a welder) I'm just having a hard time visualizing it.


I want to thank all you guys for your help!!!! sometimes you need a little push to build confidence even though you know your more than capable of it

 

[Pandaman]

I'm currently at work and wont be home untill next weekend 23.08.2004, if you can wait that long I would be happy to post some pics for you.

 

[KawieKX125]

No need to make a tool, get a stack of LARGE washers with the ID bigger than the inside of the crank, use about 2 inches worth of them. Then get a few other washer and a fender washer and a bolt and when you put it all on top of the left side of the crank, you can use the bolt to pull the crank through.

 

[reelrazor]

I have been using the method eric gorr recommends for years without any hassle or drama. That is; torch on the bearing pocket of the cases, drop in cold bearings, let sit til cool, install seals, frozen crank, heat aluminum slug that fits nicely in the inner bearing race to expand the right bearing, drop cold crank in the right side, apply sealer if necesary to the cases, repeat slug heating trick on left bearing inner race, drop left case on. Make sure everything is lined up, lightly tap case down with plastic mallet. The whole process takes twenty minutes(excluding last clean/prep time).

In 19 years I have never had to use a crank puller tool.

 

[SULLY]

Reelrazor is right use heat/cool method. Some manufacturesrs are tighter than others for some reason KX's seem to have very tight cases, particularly the mini bikes.