Putting My Motor Back Together School Me???

Okay I'm completing my first bottom end tear down on my 2000 YZ250 Monday when the remainder of my parts show up. I had to split the case due to 2 bad shift forks and 4 bad gears. While in there I'm replacing crank seals and main bearings. Also replacing crank rod and piston and case half oring. Anyways if you have any tips to give me secrets or advice so I make sure it's done right the first time let me have them. I did read something about copper coating the head gasket what about the base gasket? Any advice would be appreciated as far as building a motor back up goes. I have done tons of research just wanna make sure I don't miss any tips. I do have a manual.

when you put the cases back together are there gaskets? You might need to get some gasket replacer. just making sure you dont get all the way to putting the cases together and have forgotten that :smirk:

Use the correct torque specs... and remember to loc tite your primary drive bolt. Ive seen too many times people forget to torque and loc tite them and they back themselves back out through the case.

Another thing that will make life easier in the future, if you have a couple bucks to spare... Replace every phillips head screw on the bike with a allen head. I started doing this after I had to take the phillip heads out of a motor that had never been torn apart and all but one of them stripped out. Never had an allen head strip out on me.

dont forget the oring seal that sits under the bushing on the counter shaft.....it happens.

dont go too crazy with the 3 bond, and if you think you are going to be pressed for time, consider locktite flange sealant. it is anerobic so you have all the time in the world to fit the case.

I have a tube of Hondabond to put it back together I'm having my buddy's at the shop put the case halts together so they can visually check things before it goes back together! If my bike runs when I get done I'll have way more confidence next build. I replaced my powervalve and carb bolt with Allen head so far thanks. I'll make sure and loctite that primary gear!

I just rebuilt my 2000 YZ250 bottom and top end. I was going to suggest getting a crankshaft puller but if your having mechanics do it then you really have no worries. I sweated mine and it worked ok but next time I'm investing in the puller. Also use Hondabond / Yamabond 3, not 4. Just use the gaskets the bike calls for don't add anything to them.

Okay thank you for the advice but why not use the hondabond 4?

nothing wrong with hondabond.

When installig the piston do I need to make sure its dry or lubed the cylinder or piston?

When installig the piston do I need to make sure its dry or lubed the cylinder or piston?

Lube, lube, lube.

I never understood the dry-install method that many swear by.

that's what I did, I just got some raw 2t oil on my hand and rubbed it on the cylinder walls. Don't forget the oil the piston wristpin and bearing as well.

I would rather foul a plug from too much assembly lube then wonder what I am hurting by dry fireing.

Thanks guys I'll be starting the build back tomorrow when my case half oring comes in and my last two gears!

Well I got the transmission all back together except for the last gear the 27 tooth first gear wheel I forgot to order. So I one dayed it it should be hear tomorrow.

I see most rebuilds they install the clutch and mag while motors out of the bike? It's okay since I don't have the holding tool I can wait and install this stuff with the motor back in the bike right? I used 5th gear and hold rear break when removing these items!

Went to put the cases back together and woulnt seat. Anyway I had the shift drum backwards dang it. So putting the cases back together tonight then putting it all back together tomorrow so fingers crossed it'll be running friday.

Just as a tip, shift through all gears before putting the engine back in. Also move the crankshaft and see if all moves nice and smooth.

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