Dirt bikes - yamaha 125cc ttr - how expensive is it to replace the bearings?

my 14 yr old son just bought a yamaha 125cc ttr dirt bike. we replaced the sprockets and chain...

my 14 yr old son just bought a yamaha 125cc ttr dirt bike. we replaced the sprockets and chain. the person who worked on it says the bearing(s) probably are going bad. how expensive and is it worth it to have it fixed?

thanks,
Gail.

the bearings can be assesed by getting the bike elevated and the rear wheel free. When doing that try to move the wheel from left to right.
And if there is any play at all, then yes the bearings are failing and i would definately get them replaced out. But if you cannot get any play around the axle area i may not worry about it as much and possibley just keep an eye on it. But if they are out, that can prematurely wear the new chain and sprockets both. As well as be a hazard with the rear brakes. If that rear hub doesnt stay centered with the axle the the drum brake can bind up and cause faulting there as well.

as far as cost goes. That may vary a little bit. Because shop rates vary. But take your dealerships shop rate and account for about an hour or 1.5 hours of labor time plus the cost of bearings and seals. Bearings run about 17$ and there are two of those. And seals those run around 7$ and there is only one possibly two of them. So for instance if you took it to a shop with 70$ an hour you can possibly say around 100$ for labor plus approx. 50$ for parts. Seems like alot but again these are pretty vital for keeping the rear drivetrain intact.

thank you, I guess I wasn't clear on what I needed help with. The bearings I am referring to are the crank shaft bearing(s). I think that may require more time?
thanks,
Gail.

yes, unfortunately the labor time is what is going to be the major part of the bill on this. The parts may be at or below $100. But labor may run you about 5 hrs approx. And that may send you around the $400. If this does run into an approx $500 bill it is a good bike. And i think the value would still hold over that. And finding one like it that isnt ran to the ground will be more then what the shop bill is to pay for yours. As far as comparison to a shop bill versus bike value.

Thank you very much. It's what we thought.

Crank bearings on those bikes are very durable. But until it is torn down and inspected properly its hard to say.
Good luck with your ttr. A very fun bike!

they said that without proper maint, like changing the oil would make it go bad?

yes and no. Yes you definately need to keep up on the oil changes.
Rideing habits differ so looking at the oil quality on the dipstick can help determine the intervals. But usually if oil was the issue the top end, or piston usually is the first to show signs of wear before the bottom bearings.
But also another area of concern would be the top side of the crank rod. If this gets starved of oil it can also sound like a bottom noise or worn bearings.
If that were the case usually the crankshaft is replaced. This would still be the same amount of labor as replaceing the bearings, just may be a little bit more in parts. Again, haveing it inspected is the only true way to know what you are looking at. These are just some observations that are usually common with poor oil quality or low oil level.