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.
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
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.
@@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
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?
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.
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.
The PO did rebuild the crank at some point and Im wandering if he put the mains in wrong, should the bearings be facing up so you can see the brand and numbers or down so you cant read them?
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
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
