03 yz125 help

lcgordon711
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4/4/2018 6:15am Edited Date/Time 4/4/2018 2:46pm
Couple questions I have about my bike?

Can I use keihin pilot jets in the mikuni carb? They look close to the same.
If the main jet does not have a number on it is there any way of knowing what size it is?
Can I use a 08 yz450 front brake master cylinder? What about the whole front brake assembly. I’m guessing it won’t match up.

How do I change this part of the front brake back to stock so I can use a stock lever? Buy the new plunger assembly?




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mattyhamz2
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4/4/2018 7:37am
You should be able to run the 08 450 front brake set up, but you'll need to check out 2005 yz fork guards and the brake hose clamp. The 03 setup goes under the forks where the 08 would run to the inside of the fork leg.
lcgordon711
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4/4/2018 7:40am
Cool thanks not sure if I will do that or not but I think I have all the parts for it.

mattyhamz2
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4/4/2018 7:45am
Cool thanks not sure if I will do that or not but I think I have all the parts for it.

Another option is take the clamps and forks from your 450 and get the stem pressed out of your 03 clamps and into your 450 clamps and swap the entire front end on to the 125. SSS setup at no cost to you other than having someone swap stems
lcgordon711
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4/4/2018 7:54am
Yeah I actually am parting out my 08 and already have all that stuff sold or down payment atleast. Kinda needed the money since I had to buy a new 450. Still have the front brake set up though.

The Shop

lcgordon711
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4/4/2018 8:13am Edited Date/Time 4/4/2018 8:14am
Never mind I looked back through my messages and the brake is going with the front end haha.

Any body know about the jets or the 03 brake pin thing?
mattyhamz2
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4/4/2018 8:26am
Yeah I actually am parting out my 08 and already have all that stuff sold or down payment atleast. Kinda needed the money since I had...
Yeah I actually am parting out my 08 and already have all that stuff sold or down payment atleast. Kinda needed the money since I had to buy a new 450. Still have the front brake set up though.
Gotcha. Bummer because the forks would have been awesome on the 125. Check into the 05 fork guards though. They should work
RyanLester761
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4/4/2018 12:58pm Edited Date/Time 4/4/2018 1:01pm
If the pilot jets have the same thread and length, I suppose they can work. I suggest getting the proper jet though. Going off memory, I'm pretty sure they are different... IDK. And for the numbers, do you have any to compare, like a 40 and 45, but you need a 42? You can buy a cheap set of precision plug gage pins. (.011"-.060" size) Then, probe each jet to find out the size of the thru holes. I use them for cleaning clogged jets. They are handy. You would need tiny drill bits if you need to make one bigger. If you aren't in a rush, you can buy 10 pilot jets from China for like $5 on ebay.

For the front brake master, is there a C-clip inside?
lcgordon711
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4/4/2018 1:16pm
Thanks for the info. Little more info. The main has no numbers on it so I'm not sure what is in it. Maybe I should just buy a couple new jets just so I know. Says 410 is stock and I'm at 5000 ft so not sure if I should run a 400 or maybe 390 not sure. I have no experience with jetting mikuni or 125s for that matter.

The pilot is stock with a 40 and it has a 45 in it. So it is really rich. I cannot get the pilot screw to do anything and the idle screw is all the way in just to get this thing to idle.

Does anybody know where I could buy like a package of jets from like say range of 32-42 in all sizes?

What is the deal with knock off jets do they still work ok?

I have a lot of keihin jets because my other bikes all run them.

Yes I can see a C-clip inside or snap ring. Looks like you just buy a new oem rod and swap them out once you take apart the master cylinder.
RyanLester761
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4/4/2018 2:18pm
I used the knock off jets before and they're fine.
lcgordon711
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4/4/2018 2:24pm
Cool thanks for that link. I have looked before but could only find like 10-40 size jets. I need to find a different set because I will not need like 10 of those. I need like 40-30 or something.

Thanks
RyanLester761
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4/4/2018 2:38pm
Ok, no problem. If you need it fast, you can go to a dealer or find something else on Ebay. I work on a lot of bikes so I often buy in bulk. Good luck. Post some pics of your bike when you get it going.
lcgordon711
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4/4/2018 2:46pm
It goes pretty well really. It rode well this weekend. Just want to dial it in a little bit better.





Here is our crew at the track. Got the mountains in the back ground.


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