03 YZ 125 Issues

lcgordon711
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lcgordon711
Edited Date/Time 3/22/2020 7:43pm
Hi guys,
I have an 03 yz125 and it started having issues this weekend. First second on the track it starts making this bad clicking noise. Sounded like the chain was super loose and catching on something and you could kinda feel the bike grab while accelerating. I thought it was some weird chain issue so I fiddled with stuff and also shifted gears and rocked it back and forth and nothing helped. So I putted back to the truck. When I was almost back it grabbed pretty hard almost enough to kill the bike. Got it back on the stand started it up and you can hear the clicking in neutral. I was hoping it was something inside the inner clutch cover so I looked inside last night and nothing is wrong that I can see. I also drained the oil and no metallic pieces that I can see. The noise sounds to be coming more from the left transmission side and not the right or from the front like the top end or crank. I think I will have to split the cases. I have never done this but have wanted to and am excited about that part just not excited about what I may find. My question is is there something by the sound of it I should look for? I’m worried I will miss something taking it apart and when it’s apart not be able to tell any more. I will go slow I guess.
Thanks
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lcgordon711
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lcgordon711 3/5/2020 7:04am
3/5/2020 7:04am
Sorry guys if anybody looked already but I moved it over myself. Took the motor out last night and was playing with the trans. Spinning it sometimes it spun freely and sometimes it felt a few notches and some times it would hang up. When it had the notches it would make a clicking noise that sounds close to what it was doing when running. I did take the head off and look and the cylinder walls looked normal. Today I should have a little time to try to split the cases. Time will tell I guess. I hope it’s just one or two parts messed up and nothing big.
lcgordon711
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lcgordon711 3/6/2020 6:30am
3/6/2020 6:30am
Ok so split the cases last night. What looks to be third gear has 3 teeth broken off and the matching 3rd wheel has a messed up one tooth. My plan is to buy a new trans off eBay it’s 125 bucks. Then put in oem trans bearings and crank bearings and send off the crank to get rebuilt too. All that seems fine but might as well. The trans bearings seem a tad rough. Anybody have any objections to that plan? Here is a pic



Paw Paw 271
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Paw Paw 271 3/6/2020 7:17am
3/6/2020 7:17am
Replace all seals and bearings.

Paw Paw
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lcgordon711
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lcgordon711 3/6/2020 7:33am
3/6/2020 7:33am
Paw Paw 271 wrote:
Replace all seals and bearings.

Paw Paw
Yep doing that with oem. Unless another bearing is better price and same. Going to be 130 for tranny bearings and 70 for crank bearings.

The Shop

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DynoDan22
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DynoDan22 3/6/2020 9:20am
3/6/2020 9:20am
x2 Paw Paw's advice. Make sure to order all new circlips and one or two extras in case you bend one or lose one. Inspect the shift drum for wear and all shift forks. 125's do not have enough torque to shear teeth like that. That tranny was out of sync and sheared a tooth of. In other words a shift fork or shift drum was worn enough to engage two gear simultaneously and kaboom. Take it slow and measure/inspect everything. There is a reason that gear let go and it's not always the gear's fault.
lcgordon711
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lcgordon711 3/6/2020 9:45am
3/6/2020 9:45am
So basically look for wear or anything bent? Ordering a whole tranny of eBay. Just way cheaper and I’ll have an extra set of everything. 125 bucks I feel can’t be beat.

When it comes to sweating in the bearings can I put the case in a cheap aluminum tray and put in the bbq grill?

Going to go with crank works I think for crank rebuild using pro-x parts.

When you say circlips are you talking about the snap rings on the tranny gears? Or piston circlips? I

looked over some of the stuff and did not notice anything too bad but I’ll take apart and look more.

DynoDan22
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DynoDan22 3/6/2020 10:36am
3/6/2020 10:36am
I meant transmission circlips. There is always risk involved in buying a used tranny but to each their own. I would just inspect and measure each part and replace what's necessary with new OEM parts but that's my opinion.
lcgordon711
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lcgordon711 3/6/2020 10:46am
3/6/2020 10:46am
DynoDan22 wrote:
I meant transmission circlips. There is always risk involved in buying a used tranny but to each their own. I would just inspect and measure each...
I meant transmission circlips. There is always risk involved in buying a used tranny but to each their own. I would just inspect and measure each part and replace what's necessary with new OEM parts but that's my opinion.
I can take apart my tranny and inspect. The way I look at it is my gears are used with unknown quantity of hours what’s the diff between that and some used ones I buy. I could have a whole extra set with extra shift forks and drum and pins for the same price as 2 new gears. How do you measure? Does it go over that in the manual? I have a manual coming in the mail currently.
DynoDan22
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DynoDan22 3/6/2020 11:21am
3/6/2020 11:21am
The factory manual does a good job of showing what to measure.
lcgordon711
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lcgordon711 3/13/2020 7:52am
3/13/2020 7:52am
Couple questions when replacing bearings.
Can I hear in bbq grill in a alum pan? To what temp?
What if bearing drops half way in? Can I use old bearing to tap in new one? This was showed to be ok in rocky mtn bearing replacement vid.
I’m going to replace the little tranny bearings also is that smart? Do they go into just like the big ones?
Should I put assembly lube into all bearings once in?
Should i put anything around outer races when installing bearings?
lcgordon711
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lcgordon711 3/18/2020 8:22am
3/18/2020 8:22am
Anybody have any suggestions for the above questions. I’m getting close to needing to start putting back together.
navyslideby
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navyslideby 3/18/2020 12:14pm
3/18/2020 12:14pm Edited Date/Time 3/18/2020 12:15pm
lcgordon711 wrote:
Couple questions when replacing bearings. Can I hear in bbq grill in a alum pan? To what temp? What if bearing drops half way in? Can...
Couple questions when replacing bearings.
Can I hear in bbq grill in a alum pan? To what temp?
What if bearing drops half way in? Can I use old bearing to tap in new one? This was showed to be ok in rocky mtn bearing replacement vid.
I’m going to replace the little tranny bearings also is that smart? Do they go into just like the big ones?
Should I put assembly lube into all bearings once in?
Should i put anything around outer races when installing bearings?
Ummmmmm, You can use the bbq if you have a temp gauge and can get the case on an upper rack or something. Heat to like 250 or 300. But if you dont have an upper rack further from heat source, I wouldnt. Honestly an oven is a better bet if you can.... otherwise, get the case far from the burners....
Yes you can tap the new bearing in with a socket that fits the outer race or old bearing.
If you have all the bearings, replace them all! They pretty much all go in the same. Some fight more than others.... is what it is.
I put assembly lube on my bearings when I installed them just in case. Dont know that it was necessary but cant hurt.
I dont know what you mean by putting something around the outer race?
lcgordon711
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lcgordon711 3/18/2020 12:23pm
3/18/2020 12:23pm
navyslideby wrote:
Ummmmmm, You can use the bbq if you have a temp gauge and can get the case on an upper rack or something. Heat to like...
Ummmmmm, You can use the bbq if you have a temp gauge and can get the case on an upper rack or something. Heat to like 250 or 300. But if you dont have an upper rack further from heat source, I wouldnt. Honestly an oven is a better bet if you can.... otherwise, get the case far from the burners....
Yes you can tap the new bearing in with a socket that fits the outer race or old bearing.
If you have all the bearings, replace them all! They pretty much all go in the same. Some fight more than others.... is what it is.
I put assembly lube on my bearings when I installed them just in case. Dont know that it was necessary but cant hurt.
I dont know what you mean by putting something around the outer race?
Awesome thank you so much for getting back to me. First time splitting cases and doing bottom end rebuild so trying to not screw it up extremely bad. I will not be able to use an oven. I already know I’ll be killed if I use that. I’ll get the grill on extremely low and get it up to temp first. When I say around the outer race like do I put grease around the outside so it slides in the case better. Also saw to keep from spinning the bearing you can use red loctite.

Couple more questions how long would you keep the case in the (heat source) at say 275. Just an estimate of how long it takes to heat up. 1,5,10,20 min?

When the bearings are in and back together do you run some tranny oil inside the bearings to lube before start up?

Thanks so much. This is a bit scary of a deal but so exciting at the same time cuz it’s so interesting.
lcgordon711
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lcgordon711 3/22/2020 7:39am
3/22/2020 7:39am
I am struggling to find this bearing in parts catalog. It’s the small one in this pic. It’s on the right side case on the outside just above the crank bearing.
CarlinoJoeVideo
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CarlinoJoeVideo 3/22/2020 8:33am
3/22/2020 8:33am
I hear my case for 5-10 minutes.

But the bearings in the freezer for 30 minutes.

I use assembly lube on all bearings to lube them and to help them slide in.Something like this:


Not sure what you meant by using red loctite to stop the bearing from spinning?

Overall it’s a fun process, watch the videos and read the service manual if you can find it. Take your time and it’s very gratifying once it’s done and you know you’ve built a beast!
lcgordon711
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lcgordon711 3/22/2020 9:27am
3/22/2020 9:27am
CarlinoJoeVideo wrote:
I hear my case for 5-10 minutes. But the bearings in the freezer for 30 minutes. I use assembly lube on all bearings to lube them...
I hear my case for 5-10 minutes.

But the bearings in the freezer for 30 minutes.

I use assembly lube on all bearings to lube them and to help them slide in.Something like this:


Not sure what you meant by using red loctite to stop the bearing from spinning?

Overall it’s a fun process, watch the videos and read the service manual if you can find it. Take your time and it’s very gratifying once it’s done and you know you’ve built a beast!
Thanks for that info. I should be good to go. Need to get the crank sent off this week. It takes a while but I’m trying to go slow and not mess anything up
lcgordon711
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lcgordon711 3/22/2020 1:34pm
3/22/2020 1:34pm
tylerbernauer wrote:
93300-60814-00

That should be the PN for that small bearing. Its in the governor part fiche.
https://www.partzilla.com/catalog/yamaha/motorcycle/2003/yz125-yz125r/g…
Thanks I thought that was it but was not sure and wanted to make sure. I’m glad my blind bearing puller goes that small

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navyslideby
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navyslideby 3/22/2020 5:50pm
3/22/2020 5:50pm
No grease and no loctite..... and I would heat your case for about 15 minutes. I leave the bearings in the freezer overnight, the colder they are the better. And I put assembly lube in the bearings for that 1st start.
Sorry for the delay, was riding and camping in the Ocala National forest!
lcgordon711
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lcgordon711 3/22/2020 7:43pm
3/22/2020 7:43pm
No worries thanks. I think I got all the info I need for now. Need to get the crank shipped off but keep being lazy.

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