Yz125 problems?

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11/22/2017 9:39 AM

I will be buying a 2006 Yz125 this weekend. Bike looks decent and nothing leaks, or looks too rough. The owner, who is a girl, said she only got to take it out a few times this year on trails. She said the previous owner had a top end done on it with supposedly only an hour on it.. So I'm obviously gonna check the top end and crank play. But are there any common problems with Yz125s from around these years? I've heard that they're usually very reliable.

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11/22/2017 12:40 PM
Edited Date/Time: 11/22/2017 12:40 PM

2005's and 2006's had known shift stopper problems; The new wheel-style has since superseded the old ball-bearing one. I lost a set of cases and gears due to this very problem...Besides that, they're typically quite reliable. Make sure it has the newer "SSS" suspension and not the one year 2005 stuff


https://thumpertalk.com/forums/topic/512858-replace-your-shift-stopper/

http://www.vitalmx.com/forums/Moto-Related,20/Yz-125-Issues,1198546

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11/22/2017 1:41 PM

crc245 wrote:

2005's and 2006's had known shift stopper problems; The new wheel-style has since superseded the old ball-bearing one. I lost a set of cases and gears due to this very problem...Besides that, they're typically quite reliable. Make sure it has the newer "SSS" suspension and not the one year 2005 stuff


https://thumpertalk.com/forums/topic/512858-replace-your-shift-stopper/

http://www.vitalmx.com/forums/Moto-Related,20/Yz-125-Issues,1198546

That's exactly what I just read, so I'll definitely be doing that. Other than that, aren't the bikes pretty damn good? I've heard nothing bad about them, except about the shift stopper. Also wondering what good jetting would be for stock exhaust and elevation at 1000 feet, if you could help me out with that.

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11/22/2017 6:36 PM

PC is usually pretty close on specs: https://www.procircuit.com/jettingspecs2.htm


I'm at 410M, 40P, 2AS, 3rd position for most Socal tracks with OE needle on my 2006. Running 50/50 pump and 110 leaded with Bill's Pipe/Silencer and a Vforce3; This should be fine for stock setup as well. In 2011, I believe, Yamaha went to richer global specs on the jetting (and a needle change). They're good bikes cool

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11/23/2017 9:24 AM

crc245 wrote:

PC is usually pretty close on specs: https://www.procircuit.com/jettingspecs2.htm


I'm at 410M, 40P, 2AS, 3rd position for most Socal tracks with OE needle on my 2006. Running 50/50 pump and 110 leaded with Bill's Pipe/Silencer and a Vforce3; This should be fine for stock setup as well. In 2011, I believe, Yamaha went to richer global specs on the jetting (and a needle change). They're good bikes cool

crc245 has you squared away here. The jetting he's running is essentially stock for a 2006 and the stock is really very good. When I had the stock pipe I tried going in both directions richer and leaner, main, pilot, needle.. basically played around with everything and ended back up at stock. When I put on an FMF pipe or a Bill's pipe and Boyesen Pro reeds I ended up at a 400 main and 42.5 pilot. If it's hot out or I am at 4,500 ft or better I can drop to a 390 main. All of this is based on running 32:1. If you run a different ratio it will affect your jetting.

I tried a V-Force reed block and it leaked and sucked air. If you use one of these make sure you seal it up good with Moto-Seal, Ultra-Grey, or some other gas-proof sealant.

As far as other things, the inner clutch hub gets notched pretty easily. Luckily they aren't too expensive. I am on my 3rd or 4th one. The top head bearing seal is a known issue. It allows water past and you end up with a rusty, notchy head bearing. Be careful when washing the bike and use the seal from the YZ250F when you change it. It has a different lip that seals better. Do not run your chain too tight. There is a known issue with the cases breaking around the countershaft bearing. There is another thread on here detailing it. If you weigh more than about 165 or are reasonably fast try to get the stock springs from a YZ250 front and back. Big improvement.

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Powerband in every gear !

11/23/2017 2:19 PM

Thank you guys for all the replies, I really appreciate it. Will definitely help me with getting this bike dialed in.

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