rebuilding bottom end (I need help please!!!)

[schmanman]

I have split the cases, and I need to get the shift forks lined up with the shift drum, and get some gasket sealer on the edges of the case, but but getting the cases to go together all the way is giving me trouble! does anyone have tips or suggestions? the motor has been apart since fall, and I'm itching to get the bike back together.

any help would be greatly appreciated!

thanks!!!

-Alex

EDIT: the bike is a 1987 yz 250, if that helps. not sure how I forgot to include that!

 

[kx2502009]

make sure the gear shift drum and trans shaft are lined up to go in the other case half and you may not have something together correct and the cases must be pressed on with a press

 

[whenfoxforks-ruled]

Are you trying to put it together on its right side? You can be inadvertently pushing the counter shaft out. Are you sure the shafts are all the way to the right side? Spin them, and get a good light to be sure its all the way in. Sometimes the gears are not meshed exactly right, specifically the ones that the forks move. You should be able to go through the gears if you are careful. On most, it sure seems the washers on the left end are about even, and the fork pins are all the way in, and straight. Then carefully draw the cases together, and frequently spin the shafts to make sure they are free. The freeze the crank and warm the cases or slug help a ton, literally Vintage Bob

 

[schmanman]

ok, thanks a lot guys. this should help. I was hoping the cases required a press, I haven't been using one.

what kind of sealant would you recommend for the seam?

 

[whenfoxforks-ruled]

Some are very difficult to draw together, especially when they are the same temperature. I use a set of big c clamps at the motor mount area, and/or draw them together with the screws. If its a Honda, use Honda bond. If its a Suzuki, use Suzuki bond? Joking, any of the thin fast drying gasket sealers, some have silicone? Vintage Bob

 

[kx2502009]

i have tried regular gasket seal none of it works it sucked taking the motor back apart but now i always use suzuki bond kinda of pricey for some gasket sealer but holds up great with no leaks

 

[whenfoxforks-ruled]

i have tried regular gasket seal none of it works it sucked taking the motor back apart but now i always use suzuki bond kinda of pricey for some gasket sealer but holds up great with no leaks

In no way is it pricey. Try buying the white silicone gasket bond, its like 3 times the price. And everyone swears its better. I know its messier! I have never had a problem with the usual stuff. Vintage Bob

 

[schmanman]

thanks a lot for the help guys!

the knowledge on this site has helped me tremendously!

 

[Porkchop]

I have seen the product, "Yamabond"seemingly duplicated by a couple of different companies.
Wurth, a german based industrial supply co. has a sealer spooge similar to y-bond,it's pricey too. Permatex has one too, Item #29132, " Motoseal, ultimate gasket maker, GREY ", not too pricey & found in auto parts stores. All 3 spooges are good & look, apply & do the same thing. A good friend of mine that owns a wholesale transmission rebuilding co, says the original concoction for the spooge was german developed & licensed or copied by the other companies, the only difference is the retail price.
As Bob has advised, freezing the crank/ trans side of the cases, & warming the other side that you are assembling is necessary due to the exact diametrical measurement of the crankshaft fit in the main bearing, when both are at the same temperature.
Aprox 125 to 150 degree f will do ok. Apply the sealer to the cold parts after drying any ice or condensation from the gasket surfaces. Be sure that all the internals are lined up properly & spin tested as you tap them together with a dead blow mallet or a rubber or leather mallet. I would advise against using a press, if something is not right, you may bend or break parts. Do not be concerned with any disassembly issues of one sealer over an other, the objective is to result with it all sealed & assembled perfectly. Gaskets are cheap in comparison to your time & effort.
Good Luck! :ride: :cool:

 

[2strokerfun]

If your cases have a gasket and the mating surfaces are smooth and not scarred up, I prefer a light coat of grease instead of sealant. Yes, grease. With smooth mating surfaces, the grease helps swell the gasket slightly to insure a good seal. And when it is time to rebuild, it is usually fairly easy to peal gasket and clean surfaces. If the cases do not use a gasket, I normally prefer Yamabond.

 

[whenfoxforks-ruled]

If you have gaskets, you should not need sealer? Reconditioning old gaskets or over kill? Properly maintained, I have never had an issue with the basic procedures. Used stuff, buggered up by others, all of the above and a prayer! Vintage Bob

 

[schmanman]

nope, no gasket on these cases. that would simplify things a lot, but no such luck

 

[whenfoxforks-ruled]

Gaskets: parts I really do not need, and pay for. Vintage Bob