Part 12: Assembling dirt bike motor bottom end mating cases 1. YZ250F example

[denning12591]

Why use a press? I have a tusk crank puller meant for pulling the crank through the crank case. $60 well spent. Also have the tusk crankcase splitter. Another 60 well spent

[jroweapd]

John when I split the case on my bike 01 426 will I need a case gasket or will this yamaha 4 stuff work without a gasket

[Johnnysshop]

@jroweapd Depends on if it has a gasket or not. Most of the bikes I've done do have a gasket but this one doesn't call for one. I don't believe the 426 using one either but I may be incorrect. If it doesn't, the Yamabond works great.

[Sumrack9]

I've just assembled my yamaha jog r scooter crank case, after inserting my crank.. I had to press the other crank case back on the main crankcase (with a special tool - Needs lots of power), because of the very little diameter difference between the crankshaft and the crankbearing.. How come u just "put" the other case on the main, without using a lot of power? Isn't the crankbearing a little too big for the crank then?

[Johnnysshop]

@Sumrack9 Really depends on the bike. Was it a 2 stroke? If so, every 2 stroke I've done has needed a press.

[Sumrack9]

@Johnnysshop Yes, it was. Then that's probably it. thx for the reply. :)

[ben1996ful]

i took my 06 yz250f in for a topend rebuild and when the shop took it apart they called me and the bottem end needed to be done aswell so they took that apart and called again and the new and used dealer i brought it of had welded some steel on to the side of a bearing to hold it in place and some of it has chipped of and cracked one of my cases so i am not very happy about that

[Johnnysshop]

@ben1996ful Man that isn't good. How much did it end up costing you?

[ben1996ful]

@Johnnysshop if i went ahead with it it would cost $5000 but i am only getting a topend done on it and then trading it for a brand new rm250 2t

[Johnnysshop]

@ben1996ful Wow, 5k... You could buy a new one!

[B0DYR0T]

Johnnysshop, I thought you are supposed to apply Yamabond to each side of the case, then let it get goopy, then assemble? Good video though my man.

[Johnnysshop]

@B0DYR0T Hmm.. Not sure, I've never done it that way. Thanks for watching!

[pmkfrtscvo]

i went and pulled the kick starter gear and such without thinking, when iput it back on, the gear on it, jus moved freely? is it suppose to? if not, how do i fix it?

[Johnnysshop]

@pmkfrtscvo Hmm.. Are you sure it's seated all the way?

[smalltownpower]

i've rebuilt a few 2 stroke snowmobile engines and so far none of them have a gasket between the two halves. they mostly use threebond or yamalube 49(even on a bombardier productt) or loctite 515...which i think was changed to loctite 518. their anerobic sealers and will only seal in the absence of air, so the remaining that gets squeezed out usually gets burned off. so dont bitch cuz thats how they come from factory...without case half gaskets

[davison1021]

hey i have a hole right behind my engine i can see right down into my tranny gears it not a broken hole it looks like a vent or i dont know is this normal?

[Johnnysshop]

@davison1021 Not normal to have a hole... Sounds like a plug or something is missing. Post some pics.

[nizmojoeblows]

who at yamaha designed that engine without a gasket between the cases? really dumb....they are MAKING you fuck up your engine with that goop.....KISS OF DEATH FOR ANY ENGINE is seeing that goop on the outside of the cases....if its outside it--its inside it too,and thats bad.....IF YOU PROPERLY INSTALL A GASKET YOU SHOULD NEVER NEED TO USE GASKET SEALER.

[Johnnysshop]

@nizmojoeblows I agree. The goob was there from the factory as well. If they had a gasket kit I would prefer to use that but they don't. Oh well...

[nizmojoeblows]

@Johnnysshop ya not much ya can do really. great videos BTW!!

[Johnnysshop]

@nizmojoeblows Thanks!

[lollol587]

@Johnnysshop i have a couple of question if you dont mind ... i might buy a yz 125 its a bit out of shape ... how much did you pays for the rims and could i get the aluminium frame cover and head cover for a yz 125 ?

thanks and nice vids !!

[Johnnysshop]

@lollol587 The rims where $550 or so. You mean frame guards or the engine guards?

[lollol587]

@Johnnysshop yes the engine guards and frame guards 

[Johnnysshop]

@lollol587 Yeah, you should be able to get them on eBay depending on the year. That's where I got all my engine guards.

[BAKARDAN1]

do i need to dry the liquid gasket before assembling ?

[Johnnysshop]

@BAKARDAN1 No

[twhiff3344]

how would it cost to rebuild the bottom end of a kx 450f 2006

[Johnnysshop]

@twhiff3344 Entire bottom end crank, piston, rod, bearings, etc with labor would probably run 800-1k more than likely.

[loop1612]

Hi! Nice work XD! I reassembled many 2 stroke motocross engine but not 4 stroke and i saw that in 2 stroke when i assembly the case, they are very very hard for approach because the interference between bearing and crankshaft is very little and i use a particular tool. But i saw that you reassembled your case easily, this because in the 4 stroke the interferece is more?How did you do?

Thank's and excuse me for my english! BYE BYE

[Johnnysshop]

@loop1612 Overall the 4 stroke is a way more complicated built except for splitting the cases. Every 4 stroke I've done has been easy. Every 2 stroke I've done has required the use of a case splitter.

[blazerblast]

i'm supprised you dont need a gasket in between the cases.

[Johnnysshop]

@blazerblast Yeah, Honda is one of the few that do use gaskets now actually. Wish they all did.

[blazerblast]

always with you,great video very very informative and visual video,thx again for a great video

[Johnnysshop]

@blazerblast Thanks!