Bearing failure behind front sprocket

keeptwostrokesalive
Edited Date/Time 2/11/2015 6:26pm
So yesterday I was out at my local track practicing on a perfectly groomed track, getting ready for the race(which was today) when oil started leaking from behind my front sprocket. At first it was just a very small amount, so I figured it was most likely just a faulty seal and I could ride a little bit longer before calling it a day. I rode a few more laps only to stop and find out the bike was pouring oil from behind the sprocket now with VERY fine metal shavings mixed in to the oil. I immedietly packed up and took it too a buddy of mines shop to discover the bearing inside the engine behind the sprocket was completely shotPinch Now I'm in the process of taking my motor out to have the cases split, but I'm having trouble locating the bearing that I need on rockymountains OEM. Is this bearing connected to the crank, or is it in an entirely different position? I have never done a bottom end on any of my bikes so I am very unfamiliar with that area. Bike is a 2006 yz250
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slipdog
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slipdog 2/8/2015 1:42pm
2/8/2015 1:42pm
The seal and bearing will be listed under the transmission section.
Paw Paw 271
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Paw Paw 271 2/8/2015 2:33pm
2/8/2015 2:33pm
http://www.bikebandit.com/oem-parts/2006-yamaha-yz250-yz250v/o/m145162#…

You need parts 24, 25 26 & 27 from the transmission drawing.

Understand that if this bearing went bad then you may also have trash in the other bearings as well. Now that you have to split the case, why not just change all of the bearings and the seals to be 100% sure?

Paw Paw
keeptwostrokesalive 2/8/2015 5:07pm
2/8/2015 5:07pm
Paw Paw 271 wrote:
http://www.bikebandit.com/oem-parts/2006-yamaha-yz250-yz250v/o/m145162#sch529974 You need parts 24, 25 26 & 27 from the transmission drawing. Understand that if this bearing went bad then you may also have trash...
http://www.bikebandit.com/oem-parts/2006-yamaha-yz250-yz250v/o/m145162#…

You need parts 24, 25 26 & 27 from the transmission drawing.

Understand that if this bearing went bad then you may also have trash in the other bearings as well. Now that you have to split the case, why not just change all of the bearings and the seals to be 100% sure?

Paw Paw
It wont let me pull up the page for some reason but is it the same as the ones on this site? https://www.rockymountainatvmc.com/oem-schematic/1
When I split the cases I will be inspecting and replacing everything that needs to be replaced, I may even do a bottom end rebuild while I have it all apart.

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jhansen510
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jhansen510 2/8/2015 5:41pm
2/8/2015 5:41pm
Paw Paw 271 wrote:
http://www.bikebandit.com/oem-parts/2006-yamaha-yz250-yz250v/o/m145162#sch529974 You need parts 24, 25 26 & 27 from the transmission drawing. Understand that if this bearing went bad then you may also have trash...
http://www.bikebandit.com/oem-parts/2006-yamaha-yz250-yz250v/o/m145162#…

You need parts 24, 25 26 & 27 from the transmission drawing.

Understand that if this bearing went bad then you may also have trash in the other bearings as well. Now that you have to split the case, why not just change all of the bearings and the seals to be 100% sure?

Paw Paw
keeptwostrokesalive wrote:
It wont let me pull up the page for some reason but is it the same as the ones on this site? https://www.rockymountainatvmc.com/oem-schematic/1 When I split...
It wont let me pull up the page for some reason but is it the same as the ones on this site? https://www.rockymountainatvmc.com/oem-schematic/1
When I split the cases I will be inspecting and replacing everything that needs to be replaced, I may even do a bottom end rebuild while I have it all apart.
May? If your going in go all the way. When was the crank last replaced?
jmpatt79
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jmpatt79 2/8/2015 7:26pm
2/8/2015 7:26pm
if your digging that deep , just do a bottom end !!!!
keeptwostrokesalive 2/9/2015 3:27am
2/9/2015 3:27am
Believe me I REALLY want to do the bottom end too, but money is very tight for me right now. College and motocross is not a good combinationPinch
Gooose
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Gooose 2/9/2015 7:15pm
2/9/2015 7:15pm
If u could've see metal shavings in the oil leaking out its definitely in other bearings too. It may not b cheap now but its much cheaper than something major failing and being laid up somewhere later for a few months.
jmpatt79
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jmpatt79 2/9/2015 7:45pm
2/9/2015 7:45pm
if money is tight brake clean the crap out of all the bearings , and take the seal and bearing you need to the local bearing supply house and match up seal and bearing , i would use a NTN bearing if i was you ............and put it all back together
jhansen510
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jhansen510 2/9/2015 8:22pm
2/9/2015 8:22pm
Like I said before? When was the last bottom end job? Surely you have enough things laying around you can go to craigslist with to scrape up some funds. That's what I always did in a pinch back in the day. My suggestion is to source your own bearings and seals and get the crank rebuilt. Do the labor yourself. It is not a difficult job with a service manual. The cheaper route can often end up being much more expensive.
keeptwostrokesalive 2/10/2015 5:58am
2/10/2015 5:58am
jhansen510 wrote:
Like I said before? When was the last bottom end job? Surely you have enough things laying around you can go to craigslist with to scrape...
Like I said before? When was the last bottom end job? Surely you have enough things laying around you can go to craigslist with to scrape up some funds. That's what I always did in a pinch back in the day. My suggestion is to source your own bearings and seals and get the crank rebuilt. Do the labor yourself. It is not a difficult job with a service manual. The cheaper route can often end up being much more expensive.
I'm already in the process of parting out a 2000 kx250 for extra money, and yes I will do all of the work my self. Except for splitting the cases, I have a buddy that will do that for me. The guy I purchased the bike from 2 years ago redid the bottom end, so yes it has been a while. The problem I thst I need new swingarm bearings too and they aren't cheap, but I will do Whateve it takes to get the bottom end rebuilt too
keeptwostrokesalive 2/10/2015 6:00am
2/10/2015 6:00am
eBay is going to be my best friend for most of my parts too, it's not the ideal choice but I can't afford to buy direct from some websites right now
BobPA
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BobPA 2/11/2015 9:09am
2/11/2015 9:09am
the countershaft seal and bearing kits are available aftermarket for maybe 25 bucks
keeptwostrokesalive 2/11/2015 6:26pm
2/11/2015 6:26pm
BobPA wrote:
the countershaft seal and bearing kits are available aftermarket for maybe 25 bucks
Where are you seeing that at? Everywhere I have looked the bearing itself is more then $25

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