YZ 125 project bike

Coach529
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5/4/2016 7:01am Edited Date/Time 5/5/2016 6:12am
Getting back into bikes after a couple years away. My boys (12 and 3 years old) are crazy about it.....and if I am going to be spending time at the track I might as well be riding.

Shopping for a YZ 125 as a project. Last one I owned was a 2000. I do not know much about them after that since I was on KTM's from 2001 until recently.



Thinking about a 2005 or newer to be on the alum chassis, although not opposed to steel either.

Any notable changes making a certain year a better option?

I have ridden a 2006 and it was a blast.



Not going to be a crazy project. Stock motor, or close to it with exhaust and possibly updated bodywork. I will be using it for some vet moto and possibly some offroad stuff.

Thanks guys.....





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5/4/2016 7:04am Edited Date/Time 5/4/2016 7:04am
Slippery slope. Before you know it, it'll be a 144.

Get an 06 or newer. Do all new Chassis bearings Rebuild engine. Get suspension done. You're golden.

My 06 144 woth 16 hours on the total overhaul. Crazy to think its 10 years old....feels new to me!

5/4/2016 7:05am


Last pic. That Or build a steely. That's popular right now....
Coach529
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5/4/2016 7:13am
I have done the hog wild thing a couple times......trying to remain under control this time.

Last time was a 2008 KTM 144. Pretty much threw my wallet at it.







I could potentially have two kids racing this summer, so the budget will be tight.
Frodad78
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5/4/2016 7:39am
I can't wait to toss the 144 kit in my 05!!

The Shop

5/4/2016 8:10am


My 08 with 2016 plastic upgrade, PC works front pipe & PC R304 shorty, which is extremely loud. I wanna put a V Force 3 reed block on it & a pair of silver Excel rims & Talon hubs.
cwtoyota
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5/4/2016 8:20am
Slippery slope. Before you know it, it'll be a 144. Get an 06 or newer. Do all new Chassis bearings Rebuild engine. Get suspension done. You're...
Slippery slope. Before you know it, it'll be a 144.

Get an 06 or newer. Do all new Chassis bearings Rebuild engine. Get suspension done. You're golden.

My 06 144 woth 16 hours on the total overhaul. Crazy to think its 10 years old....feels new to me!

2006 - 2016 models are two wheeled perfection.

Chassis bearings, seals, grease and all that makes a bike feel so tight and new. A new lever, perch and foot pegs/pins get rid of some jingle-noise and complete that new-bike feel.

I don't think the 144 is necessary if the budget is tight. That's a chunk of change that could go to things like brakes, springs and valving. Also, the 144 pistons cost a bit more each time you do a top-end. It does add a noticeable amount of power though.



5/4/2016 8:36am
Bought a entire 144 kit on Amazon for 539. Can't complain.

My next additions will be steel braided brake lines and oversized front disc. If I could get my 144 to stop like a Ktm does id be very happy!
Phillip_Lamb
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5/4/2016 9:22am
biggest change was in 05. vs the steel frame bikes the dropped almost 10 pounds and added a 6 spd (5spd from 02-04)
usafwx
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5/4/2016 10:24am
Whats everyone running for their pipe, the stock pipe seems to be perfect, but its getting pretty ugly on my end, would like to upgrade at some point but dont want to change the characteristics of the bike power wise too much. Thoughts on everyone's pipe choices?
5/4/2016 10:35am
usafwx wrote:
Whats everyone running for their pipe, the stock pipe seems to be perfect, but its getting pretty ugly on my end, would like to upgrade at...
Whats everyone running for their pipe, the stock pipe seems to be perfect, but its getting pretty ugly on my end, would like to upgrade at some point but dont want to change the characteristics of the bike power wise too much. Thoughts on everyone's pipe choices?
I found the shorty pipe gives a bit more bottom end. I had to put my OEM silencer on for my local practice track at the weekend coz the shorty is so damn loud. I did notice a slight difference but I could easily run the stock rear with the PC front.
usafwx
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5/4/2016 10:39am
I found the shorty pipe gives a bit more bottom end. I had to put my OEM silencer on for my local practice track at the...
I found the shorty pipe gives a bit more bottom end. I had to put my OEM silencer on for my local practice track at the weekend coz the shorty is so damn loud. I did notice a slight difference but I could easily run the stock rear with the PC front.
So the PC pipe, shorty?, gives you more bottom end? That would be nice since alot of times I find myself having to quick shift from 2nd to 3rd. I was under the impression the PC pipe gave you more top end. Thanks!
5/4/2016 10:51am
I found the shorty pipe gives a bit more bottom end. I had to put my OEM silencer on for my local practice track at the...
I found the shorty pipe gives a bit more bottom end. I had to put my OEM silencer on for my local practice track at the weekend coz the shorty is so damn loud. I did notice a slight difference but I could easily run the stock rear with the PC front.
usafwx wrote:
So the PC pipe, shorty?, gives you more bottom end? That would be nice since alot of times I find myself having to quick shift from...
So the PC pipe, shorty?, gives you more bottom end? That would be nice since alot of times I find myself having to quick shift from 2nd to 3rd. I was under the impression the PC pipe gave you more top end. Thanks!
The shorter the pipe the more bottom end it will produce.
Coach529
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5/4/2016 10:53am
Bought a entire 144 kit on Amazon for 539. Can't complain. My next additions will be steel braided brake lines and oversized front disc. If I...
Bought a entire 144 kit on Amazon for 539. Can't complain.

My next additions will be steel braided brake lines and oversized front disc. If I could get my 144 to stop like a Ktm does id be very happy!
What brand 144 kit?
usafwx
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5/4/2016 10:59am
The shorter the pipe the more bottom end it will produce.
Did you have to mess with jetting? Some guys say they did some say they didnt. Thanks bud.
FGR01
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5/4/2016 11:06am
My feelings on shorty mufflers... they do not add bottom end power but they give you the impression there is more because the bike feels snappier. There is less back pressure so it allows the revs to spool up quicker which most people interpret as "more bottom power". This can be useful on tighter tracks with jumps very close to corner exits. However, the shorty absolutely kills the top-end overrev. I had one on my 2006 YZ and did not like how it forced me to shift to higher gears on every straight because of falling off the power on the top. I switched to the normal length FMF powercore which is essentially about 1/2 way between the shorty and the stock silencer. Much better now.
5/4/2016 11:12am
usafwx wrote:
Did you have to mess with jetting? Some guys say they did some say they didnt. Thanks bud.
No I didn't change the jetting.
5/4/2016 11:16am
FGR01 wrote:
My feelings on shorty mufflers... they do not add bottom end power but they give you the impression there is more because the bike feels snappier...
My feelings on shorty mufflers... they do not add bottom end power but they give you the impression there is more because the bike feels snappier. There is less back pressure so it allows the revs to spool up quicker which most people interpret as "more bottom power". This can be useful on tighter tracks with jumps very close to corner exits. However, the shorty absolutely kills the top-end overrev. I had one on my 2006 YZ and did not like how it forced me to shift to higher gears on every straight because of falling off the power on the top. I switched to the normal length FMF powercore which is essentially about 1/2 way between the shorty and the stock silencer. Much better now.
I understand what you are saying. The track that I was running it on was fairly tight so it seemed to give a bit more snap at the bottom compared to my OEM. I've got a practice day later this year at a National circuit with nice long hills & it's kinda sandy do I'll try the pipes back to back.
usafwx
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5/4/2016 11:16am
No I didn't change the jetting.
Cool, might pull the trigger on a PC pipe and R304 silencer now. Thanks!
5/4/2016 11:24am
usafwx wrote:
Cool, might pull the trigger on a PC pipe and R304 silencer now. Thanks!
Just beware that the R304 is frigging loud. I need to do a db reading on it to measure exactly how loud it is.
cwtoyota
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5/4/2016 12:28pm
usafwx wrote:
Cool, might pull the trigger on a PC pipe and R304 silencer now. Thanks!
Just beware that the R304 is frigging loud. I need to do a db reading on it to measure exactly how loud it is.
...and it makes less top end / over-rev power. I like the regular old PC 304 silencer.
usafwx
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5/4/2016 1:44pm
cwtoyota wrote:
...and it makes less top end / over-rev power. I like the regular old PC 304 silencer.
So would you recommend the pc pipe with 304 over stock then?
cwtoyota
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5/4/2016 1:56pm
usafwx wrote:
So would you recommend the pc pipe with 304 over stock then?
The stock silencer makes great power. The PC 304 is a little more compact, lighter and sounds awesome. Eventually the mount will crack right off of the PC canister since they only use one bracket on the 125cc bike. It takes a lot of hours, but it always happens. I just weld on a stronger bracket when they break.

In my opinion, shorty silencers are pretty dumb for a fast 125 rider. You want top end and over-rev on a 125. The shorty adds a little more hit in the mid range at the cost of top end. The shorty feels and sounds faster, so lots of people just love them.

The FMF pipe feels like it makes a little more top-end than the PC, but you'll need a transmission-fluid funnel to fill your oil because the pipe sits lower in that area.

I like the PC 304 silencer and FMF factory fatty combo in terms of performance.
usafwx
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5/4/2016 1:59pm
Thanks!
Phillip_Lamb
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5/4/2016 2:13pm
usafwx wrote:
Whats everyone running for their pipe, the stock pipe seems to be perfect, but its getting pretty ugly on my end, would like to upgrade at...
Whats everyone running for their pipe, the stock pipe seems to be perfect, but its getting pretty ugly on my end, would like to upgrade at some point but dont want to change the characteristics of the bike power wise too much. Thoughts on everyone's pipe choices?
on my last yz125 05 i had a pc pipe/shorty, but switched to a FMF fatty, the pc pipe put out more top end so it was harder to keep in power, fmf just added everywhere, stock had a little sign off on top and it covered that but without sacking bottom end
Phillip_Lamb
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5/4/2016 2:15pm
usafwx wrote:
So would you recommend the pc pipe with 304 over stock then?
cwtoyota wrote:
The stock silencer makes great power. The PC 304 is a little more compact, lighter and sounds awesome. Eventually the mount will crack right off of...
The stock silencer makes great power. The PC 304 is a little more compact, lighter and sounds awesome. Eventually the mount will crack right off of the PC canister since they only use one bracket on the 125cc bike. It takes a lot of hours, but it always happens. I just weld on a stronger bracket when they break.

In my opinion, shorty silencers are pretty dumb for a fast 125 rider. You want top end and over-rev on a 125. The shorty adds a little more hit in the mid range at the cost of top end. The shorty feels and sounds faster, so lots of people just love them.

The FMF pipe feels like it makes a little more top-end than the PC, but you'll need a transmission-fluid funnel to fill your oil because the pipe sits lower in that area.

I like the PC 304 silencer and FMF factory fatty combo in terms of performance.
im curious as to why you're against shorties. I can remember seeing every pro bikes at hangtown with em on. of course Hangtown is a relatively tight track as opposed to washougal and unadilla
theToothPerry
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5/4/2016 2:25pm

Bought my 06 for $1100 bucks and with a little love it has become my favorite bike ive ever owned. Great Project.




5/4/2016 2:28pm
im curious as to why you're against shorties. I can remember seeing every pro bikes at hangtown with em on. of course Hangtown is a relatively...
im curious as to why you're against shorties. I can remember seeing every pro bikes at hangtown with em on. of course Hangtown is a relatively tight track as opposed to washougal and unadilla
Everyone was running them at the last EMX125 round too.
Skerby
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5/4/2016 2:45pm
Shorty 4 lyfe. I havent ever ran anything else though lol. The R304 is crazy loud! Im glad everyone else has had the same experience, i thought mine was messed up its dang loud.
cwtoyota
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5/4/2016 2:47pm
im curious as to why you're against shorties. I can remember seeing every pro bikes at hangtown with em on. of course Hangtown is a relatively...
im curious as to why you're against shorties. I can remember seeing every pro bikes at hangtown with em on. of course Hangtown is a relatively tight track as opposed to washougal and unadilla
That's just my personal opinion. I remember back in the day almost all of the national pros had a shorty on their 125. I always figured they were running different porting, fuel and exhaust temperatures than the rest of us... I feel like there is more over-rev with a longer silencer.

On a tight track like local arenacross, the shorty would probably be superior.
Underdog999
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Kalaheo, HI US
5/4/2016 3:33pm Edited Date/Time 5/4/2016 3:35pm
I found the shorty pipe gives a bit more bottom end. I had to put my OEM silencer on for my local practice track at the...
I found the shorty pipe gives a bit more bottom end. I had to put my OEM silencer on for my local practice track at the weekend coz the shorty is so damn loud. I did notice a slight difference but I could easily run the stock rear with the PC front.
usafwx wrote:
So the PC pipe, shorty?, gives you more bottom end? That would be nice since alot of times I find myself having to quick shift from...
So the PC pipe, shorty?, gives you more bottom end? That would be nice since alot of times I find myself having to quick shift from 2nd to 3rd. I was under the impression the PC pipe gave you more top end. Thanks!
I had a PC pipe and shorty on mine and switched out the shorty silencer and it was better. I hated how loud it was, and it gave me more snappy power when I put the stock silencer back on with the pc pipe. That shorty silencer is not all that great.

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