splitting cases Tri-Z/YZ250

[86350xman]

I'll start off by saying I have a manual. I have a spare Tri-Z motor that has piston pieces lost in the bottom end that I plan on splitting the cases to clean out and replace all seals and bearings and maybe even a new rod. My question is, does the transmission stay intact within the case? What all should I look out for while doing this? This is something I really want to tackle myself because after I have the tri-Z motor done, I want to go through my YZ motor too and would rather save the money by doing it myself than pay a shop to do it for me. And what is the best way to split the cases? I've heard some say a screwdriver and pry them apart, but then I've heard just as many say don't do that.

[Gdkarma]

Right or wrong by other's ideas, I tore two bottom ends apart with a rubber mallet and had no problems...................if you get all the bolts out first! There's one, somewhere, that is hard to see or know it is there, but besides that, mine came apart fairly easy. I took my time and just seperated them apart, then placed on a bench and pulled them apart from there. I "think" you want the clutch side up, as all the gears are in there.:doh: I can look at some stuff to verify, if nobody else chimes in with some suggestions. I seem to remember that the crank was a bugger to get out, and I won't give any suggestions on that!

[86350xman]

Yeah that would be great if you could verify. Thanks for all the help!!! This weekend I'm probably gonna be putting a radiator in my truck, but within the next couple of weeks I'd like to get all the parts oredered and have at least the bottom end done in this Z motor.

[likestrikes]

Most motors I have split and thats quite a few, the tranny and fork shafts will stay in either side without falling apart. Splitting cases isn't easy but not hard either. Even if you just ripped it all down, most of the gears stay on the shafts with clips. Only a couple of gears will slide off along with a thrust washer in front and or behind them. As far as which way they go back on, it's easy because there either both sides are identical OR one side will allow FULL engagement from the neighbor gear or it will only partially engage.

The big stuff is...... Stoning the 2 surfaces perfectly flat, taking them apart smoothly and even and using plastic hammers to tap things apart and or together. I have had good luck with making sure to press in the new main bearings evenly and then I use a piece of pipe over the crank to only press against the inner race of the bearing while I'm reassembling the 2 halves. I get it all together and press the seals in last. Sometimes the crank to bearing is a tight fit and too much force is on that bearing if you don't press directly on the inner race. Thats why I do it that way....