Splitting cases?

[jaybob]

OK I have a 88 KX 250 with a thrashed top and lower end.
The motor was seized at some point and the owner (not me) let it sit torn apart for a long time. Needless to say the cylinder and piston was corroded. The carb is corroded beyond repair and the bottom end is corroded as well.

Now I know that most of you will say walk away from this 14yr old piece of mouse piss drenched gobbledygook. However I may have a line on a spare carb, cylinder, and various other needed goodies for cheap. So I drove the piston to the bottom of the stroke, took off the cylinder, pulled the rest of the motor from the frame and am ready to dig into new territory.

I am not a total bike nincompoop. I can readily handle most repair and rebuild operations but this would be the first time for me to try my hand at total case deconstruction. Granted if a fatal mistake was made I could easily ditch the whole project without losing a penny. So I figure I might as well give it a go.

Does anyone have any tips for case splitting in general? I am assuming that I am going to need to take off the stator and clutch covers and remove the offending, in the way parts therein. Then remove all of the bolts holding the cases together. Are the case halves press fitted at all? I'm sure that it is a tight fit between the crank and main bearings. I am wondering how best to remove stuff so as not to damage anything?

I am currently planning on having the crank and rod assembly rebuilt and replacing the main bearings and having a replacement cylinder fixed up with a new piston and rings. I really can't afford to send this old motor out to a pro if I can possibly accomplish some of this stuff myself, as it is just a junk project anyway. But I would like to end up with a running motor.

I know that this is still going to cost a little, but hey you guys are the pros and maybe someone can help.

 

[geir54]

Well, I've just split my first case on a '92 cr 250 and I've only done a top end job before. You will probably need a flywheel puller (I bought one) and I made a case splitter out of a bar of steel and a bolt and nut and used the case bolts. IF you make one, make sure the bar is strong. I made one out of a square steel bracket. Once you split the cases, make sure you get all the spacers that go with the trans shafts cause they stick to the cases somtimes. The trickey part was trying to keep the cases halves an equal distance apart. I deadblow hammer helps for this. They run about $10-15. If you get this far and decide to rebuild it, I'd go with new crank bearings and seals because its not worth doing again. One last thing. Make sure you get all the case bolts out before you split it. I missed one by accident and it took me a while to realize why I couldn't split the cases evenly. Good luck.

 

[Weezie]

Just to add to the above, you'll have to remove the flywheel, stator, clutch covers, the clutch itself, water pump and primary gear(all the offending parts). If you don't have a manual, GET ONE. Taking it apart is the easy part, it's getting it back together that takes patience and did I mention you should get a manual. It's not all that difficult. ;) You might want to consider replacing all bearings and oil seals in the lower end. But then again you gotta ask yourself, how much do I want to spend. Is the bike worth it? I just spent around $200 for all the bearings and seals in my '92 KX. Add a crank rebuild for around $140 and you have a fresh bottom end. Good luck, Mike. :confused:

 

[jmics19067]

all the above and have a nice clean area to work in, egg cartons. rubber bands, and plastic baggies or whatever To keep all subassemblies and bolts in order. if engine is still in frame counter shaft sprocket and cover and all motor mount bolts goes in to a plastic baggie. Flywheel and all related stuff set inside flywheel cover dont lose the woodruff key! take off clutch cover any and all parts taken off that side set inside clutch cover. you get the idea pay close attention to everything you take off a digital camera or poloroid would be nice. keep everything neat and clean and organized.

 

[2001yz250]

Do yourself a favor and get a manual. It, at least, gives you confidence that you have instructions on getting it back together and you don't have to wonder, 'now where did this thing go'. Nothing worse than getting it back together and having spare parts left over that go on the transmission! :whiner: Funny story, at least it is now. I was just putting the cases back together when, right at the split second they were about to connect, the rod falls over. Ok, now I have the cases back together with a working transmission but nothing to connect the piston to! The rod was sticking into the transmission :scream: Ok, so I split the cases again. Now I'm putting them back together AGAIN, watching that rod, trying to keep the shift drum aligned and together they go. A quick once over and everthing looks A-OK. So I continue to put on the main rod, rotor and stator, clutch, piston, cylinder, etc. put the COMPLETED engine back in the back, put everything else back on the bike, radiators, etc. and have a completed bike. So now its time to fill 'er up with transmission oil, coolant and fuel and take it out for a test run. Ok first the oil, put in about 3/4 quart and what do I see? You guessed it! Fresh red Bel-Ray 75w transmission oil running out from the bottom of the motor from between the case halves. :scream: :p :whiner: Seems the case gasket had crooked just a little right before the halves came together. It took all of my will power just to keep from dowsing it with gasoline and throwin' a match on it. So, after a couple hours of cooling off and soul searching, here I go again tearing the bike completely down again. I finally did get it fixed and back together again and everything was peachy keen. Moral of this story: If you have to concentrate on remembering all the small details of what goes where, you may completely overlook the large, obvious things. Get a service manual!

 

[jaybob]

here we go

I went for it last night. I got the cases apart and the crank out. I even managed not to break anything, or the use of any tools that I did not have on hand. So far the complexity of the mechanism is a little less than I had imagined. Now a question. Is there a tool to remove the main bearings from the cases? I definitely need to have the bottom end rebuilt the bearings hardly turn, and the whole assemby is pretty rusty. I hope I can find a local shop to do it. The good news is that the tranny is in good shape.

 

[jmics19067]

use heat. warm up the area around the bearing with a propane torch. if you can guestimate about 350degrees farenhiet.

if you can the eaisest quickest way to change the bearings is to put the new bearings in a freezer. remove the dowels and bearing retainers of the bearings you want to change. clean the cases extremely well finishing up with soap and water. Blow dry with an air compressor. Heat the cases up <luckily I know someone who used to own an old Bultaco dealership and he has an oven in his shop for specific reason> to about 350 using welding gloves or oven mitts hold the case 8 10 inches away from a hard peice of wood and smack it flat against the wood . Most of the time they pop right out . If the area behind the bearing is clean then you can just drop the new bearings in while the case is still warm. Install your dowels and bearing retainers using blue loctite on the screws.

if you have everything ready, the crank and transmission all clean and set to go in, poor a little gear oil on the gears , shafts and bearings and then a little 2 stroke oil on the crank bearings .lay the right side case on 2 4x4 one under the front engine mount and one under the rear engine swingarm pivot .<if this is the case with kawasakisnot sure > put your trans and your crank in the right case . smear you sealer on stingily but making sure you cover all that needs to be sealed or line up your gasket. now just line up the left case on top . if the cases are still warm it should go right together with maybe a slight help from a rubber mallet. Install your case screws and torque. Spin the crank to make sure it rotates freely and install you shift shaft and lever and go thru the gears to make sure they are alright

Watching this being down by someone who has done it often is shear poetry in my eyes. talking 15/20 minutes from when the cases are out of the oven till youhave a complete bottom end ready to have its clutch and all put back in . The only key being organized before you start.