YZ250 Bottom End Assembly- How To / Walkthrough

Рет қаралды 6,618

Chuck Harder

9 ай бұрын

Here is a detailed walkthrough of how to do an excellent job rebuilding the bottom end on a '99 through current YZ250.

Пікірлер: 26

@camilogomez6538 8 ай бұрын

this guy really knows what he's doing

@ntinkham20 10 ай бұрын

Wow! Awesome tutorials, Chuck! I learned what I got wrong on my first bottom end rebuild years ago. The tap of the inner race of left side crank bearing to free up the crank. I'll never make that mistake again now.

@andrewdi8561 4 ай бұрын

Great video , Never new about releasing the side load , thanks for sharing your knowledge

@Dobemandan 9 ай бұрын

Nice work 👍🏻

@Thepianobird 4 ай бұрын

very informative video. At first I did think you realized the the seal can rub on the bearing. Do you have a source for the bearings? Subbed...

@ChuckfromTrueTech 4 ай бұрын

The bearings are easy to cone by if you search by size. YZ250 uses 63/28 C3 or C4 bearings. Just buy Japanese, IE: Koyo, NSK, NTN etc. I rarely buy OEM.

@RamRaidAt4am 29 күн бұрын

When you installed the clutch side crankcase seal initially it appeared that you installed it with the spring facing outwards ( as I believe it should be? ) but only moments later in the edited video it appears you reversed the seal and now the spring was facing inwards towards the crank/centre of the engine. Is the general rule not that the spring faces towards the medium that it is sealing?

@ChuckfromTrueTech 29 күн бұрын

The purpose of the crank seal is first to seal in crankcase pressure. Of course it is also responsible for preventing oil from entering the crankcase but that is secondary.

@Dsm152 2 ай бұрын

Interesting. Never thought of pulling the crank into the case via the inner race of the main bearing, if you went too far you would start to press the bearing out of the case though? I see why you choose your own method for ease of setup however it doesn’t always go that smoothly when using heat. If using heat to put cases together you have to be very well timed and ensure your puller is close by ready to go if the bearing suddenly stops. First few engines I ever built I was scraping and cleaning the yamabond off the cases and starting again

@ChuckfromTrueTech 2 ай бұрын

You won’t press the bearing out of the case, but you can put side load on the bearing the opposite way or pull the crank out of true. You’re right that it can be tricky to get the timing right with heat.

@Dsm152 2 ай бұрын

@@ChuckfromTrueTech I need to try tapping the inner race of the main bearing on this RM125 I just built, crank is very slightly resistant to turn. Used a puller on both sides to seat the crank however still not perfect. Will remove the crank seal and try hitting the bearing lightly

@motown0723 4 ай бұрын

Where do you purchase your bearings? Are they koyo?

@ChuckfromTrueTech 4 ай бұрын

I have several suppliers, but most of my bearings come from Winners Circle in Toronto. The bearings will be Japanese. Either Koyo, NSK, Nachi or NTN.

@Chris-uh3cm 8 ай бұрын

Thanks. Can I send you my engine / transmission to be worked on?

@ChuckfromTrueTech 8 ай бұрын

Definitely.

@Chris-uh3cm 8 ай бұрын

@@ChuckfromTrueTech great how can we exchange info? Do you have a website?

@ChuckfromTrueTech 8 ай бұрын

@@Chris-uh3cm Yep. www.truetechmc.com. My email is chuck@truetechmc.com.

@IBotBurchell42097 19 күн бұрын

Crank dropped in nicely, but i am worried i overheated the bearing with a heatgun 😢

@ChuckfromTrueTech 19 күн бұрын

If the bearing turned blue it’s overheated.

@IBotBurchell42097 19 күн бұрын

It didnt go blue like the bearing ive just purposely overheated, my concern is because as i rotate the crankshaft, holding the case i can can hear almost a train wheel sounding affect along with feeling holding the case, first time doing this so i am abit clueless, im probably gonna just run it and if all fails learn from my mistakes, costly tho 😅 thanks for the quick reply , and also the video helped alot thanks

@IBotBurchell42097 19 күн бұрын

Well i pushed the crank back out, I did overheat the bearing and warp it slightly not that i got it blue buttt a golden colour on one side of the inner and now has a notchy feeling on that bearing causing that feeling i was one about, as the bearing in the other case is smooth like butter, just purchased a laser heat gun temp guage lol, once again thankyou for the video