My 99 YZ125 build thread

hey guys, my names devon and i have a 1999 yz125. ive been riding for about 3 years, and this is my first bike so heres a little history.

obviously you have to take what everyone says when theyre selling a bike with a grain of salt, but "supposedly" this bike was a practice bike for the kid i bought it from's uncle, who raced for yamaha and got the bike straight from the factory. the bike was ran from 99-02, then put away until 2011. once brought back out in 2011, it was run for a year, then had a top end rebuild in winter 2011-2012, and i bought it the end of summer 2012. i picked her up for $900, with a brand new rear tire that wasn't even installed, a brand new fender, hand grips, 2 bottles of 2 stroke oil and a bottle of gear oil. it had GP racing suspension tuned for track, bills pipe, pro circuit silencer, and Tag bars. plastics obviously have some stress marks, it was a 13 year old bike. usual wear and tear, but she started up easy and ran well, putted around the yard and brought her home.

since it was my first bike and i was basically learning on it, it took me a while to start actually being able to use the power, but after 2 and a half years, i can say i can rip her hard enough to have one hell of a time. the only issue this bike has ever given me was when the clutch basket blew apart in a sand pit and wouldnt shift past 2nd gear. i thought i blew the tranny, but upon disassembling the clutch i saw what really happened.

after a new hinson racing clutch basket, clutch plate and a new DP clutch kit, and 6 cans of brakleen, she shifted through every gear perfectly. and of course, as soon as i get alllllll that back together, i blow a wheel bearing! oh well..more maintenance.

so after a total of 1 year of learning then 2 years of tearing **** up on this bike, with numerous amounts of other people beatin the piss out of it, INCLUDING winter riding last winter without rejetting, she STILL hasnt had a rebuild since ive owned her. so, i decided its about that time, before i end up with an unrebuildable bike.

luckily, i just did my rear pads and rotor, and did my front pads. i have a front rotor, and i also have a set of MSR steel bars i havent put on yet either.

so heres the plan: disassemble, have the cylinder honed, the ports ported and polished, then-
-wiseco pro lite 2 ring piston
-wiseco needle bearing
-cometic top end gasket kit with thin base gasket
-moose torque spacer
-Delta v-force 3 reeds
-heat and pressurize to fix dent in my exhaust pipe

then theres all the typical maintenance ****.
-EBC or wiseco clutch plate kit
-all balls front and rear wheel bearings
-all balls fork seals
-o ring chain and 13f-50r tooth sprockets
-twin air filter
-stator cover, bolts, and gasket (my own damn fault)
-radiator hoses (blue..just cus)
-hand grips
-plastic front and/or rear brake guards
-possibly all new plastics, but i havent decided yet

im hoping to get the parts ordered just after thanksgiving, then having all the parts there for christmas break to get the build done. this ****ty part is i can rebuild it and get all excited......but then i have to wait till march or april for the weather to warm up to properly break it in
frown.gif
cus first off i dont even know how to jet for what im modding as of right now, none the less jetting it for cold JUST to break it in?! hell nah. im just gonna wait for spring.

also once spring rolls around id like to take it to a local shop and have the suspension revalved or tuned or whatever for woods riding and my weight. anybody know what a general cost for that would run? basically a suspension tune up and mod for my weight and riding style. also, would i want to wait to do fork seals until when i go to have the suspension done? or does that not matter? thanks

i also am going to consider taking the motor out for the build so i can properly clean the outsides and in all the crevices i can, that way i can also clean the frame and possibly paint it while the motors out. i have to look into how much is left with the shock and linkages and all and how easy painting the frame is with that in, or if i need to take it out anyway to get suspension work then that will be that. but as i said, i dont know how intensive suspension rebuilds are and if they require the shock and spring to come out? guess well have to see

however, as just mentioned, i dont know much about jetting. if someone can point me in the right direction for jetting tips or suggestions based on my mods and build, please let me know! thanks for stopping by, hope you enjoy!

reserved for build updates


when i first got her


first ride out


gettin dirty


out for a ride with my buddy and his 450


redneck load up


TRX-700xx, kx250f, and the yz waitin for a wash


blew up the clutch basket...time for tacos


back in action!


lil winter action


got her a lil stuck in the ice




loading up for mountain madness


assss


mountain madness was a messsss


 
Sounds awesome! Definitely going to have to stick around throughout the rebuild, don't flake on us!

I would take the bike down to the bare frame for this rebuild. Would be silly to do all of that work and not start from the ground up. Sounds like you have some time to research jetting before you get to that point. But once you are at that point there are some knowledgeable dudes around here like Big Dan who can help ya out.

Also, WELCOME!
 
Sounds like you know what you are doing! Sweet ride, and great photos. In my experience, also some advice I got from a wise fellow. Do not do mods at the same time as rebuild. That way you know your jetting is already ballpark and can have the optimum break in period. After you get the rings seated, then do your reeds, spacers, and P&P. It's obviously up to you, but I thought I would throw it out there.
 
Tacos!!! :drool:

RRP is a local shop for me. Make sure you have a steel sleeve before you hone the cylinder. If yours is nickasil then the cylinder will be ruined with a hone.
 
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Tacos!!! :drool:

RRP is a local shop for me. Make sure you have a steel sleeve before you hone the cylinder. If yours is nickasil then the cylinder will be ruined with a hone.

really? where are you located? if im local there maybe ill have GP racing or RRP do my suspension. more likely GP since i know it has GP and RRP could just be a sticker..but then again there could be a lot of said shops in different areas lol.

i just did a quick search and found this
"After the plating is done, the bore has to be machined to the correct diameter. This machining process is what leaves the cross-hatch. If you attempt to hone a plated cylinder with a traditional hone, you will damage the bore surface. The hone can snag in the ports, chipping the edges of the plating. And instead of restoring the cross-hatch, the hone will simply smooth the ridges of the machined cross-hatch, giving you lesscross-hatch than you started with.

All you need to do with a plated cylinder is clean the bore surface with soapy water and a Scotch-Brite pad. If the cross-hatch is worn down, then the bore is worn beyond spec, and it's time for a re-plate."

that being said, basically i just need to clean the cylinder out, check out the cross hatch, if it is worn too much (which honestly i dont think will be an issue..) ill have it replated and ported and polished by my dads buddy who is a machinist. and if it doesnt need a replating, then just have it PnP'd and clean her out and go.


Sounds like you know what you are doing! Sweet ride, and great photos. In my experience, also some advice I got from a wise fellow. Do not do mods at the same time as rebuild. That way you know your jetting is already ballpark and can have the optimum break in period. After you get the rings seated, then do your reeds, spacers, and P&P. It's obviously up to you, but I thought I would throw it out there.
ok, definitely a good idea on waiting for the spacer and reeds, but the PnP would be done by the same guy who would replate my cylinder (if need be) and even still its easier just to do the PnP while the cylinder is off and everything that way you dont have to disassemble it twice
 
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really? where are you located? if im local there maybe ill have GP racing or RRP do my suspension. more likely GP since i know it has GP and RRP could just be a sticker..but then again there could be a lot of said shops in different areas lol.

i just did a quick search and found this
"After the plating is done, the bore has to be machined to the correct diameter. This machining process is what leaves the cross-hatch. If you attempt to hone a plated cylinder with a traditional hone, you will damage the bore surface. The hone can snag in the ports, chipping the edges of the plating. And instead of restoring the cross-hatch, the hone will simply smooth the ridges of the machined cross-hatch, giving you lesscross-hatch than you started with.

All you need to do with a plated cylinder is clean the bore surface with soapy water and a Scotch-Brite pad. If the cross-hatch is worn down, then the bore is worn beyond spec, and it's time for a re-plate."

that being said, basically i just need to clean the cylinder out, check out the cross hatch, if it is worn too much (which honestly i dont think will be an issue..) ill have it replated and ported and polished by my dads buddy who is a machinist. and if it doesnt need a replating, then just have it PnP'd and clean her out and go.



ok, definitely a good idea on waiting for the spacer and reeds, but the PnP would be done by the same guy who would replate my cylinder (if need be) and even still its easier just to do the PnP while the cylinder is off and everything that way you dont have to disassemble it twice


I'm in hunterdon county nj. About 20 miles from rrp. At one time rrp was at the top of the list for mods and actually built motors for a series of yammi pro guys as well as Honda satellite teams.
 
back in 1969 there were two great documentaries made: The Hellstrom Chronicles, and On Any Sunday. If you get a visor to go on that helmet you will look more like you were in the latter, than the former.
 
back in 1969 there were two great documentaries made: The Hellstrom Chronicles, and On Any Sunday. If you get a visor to go on that helmet you will look more like you were in the latter, than the former.

Actually "On Any Sunday" was released in '71, but a great documentary non the less, probably responsible for a whole generation of new dirt bike enthusiasts.
 
Hey Devon, I have absolutely no advice for you - ask any of the Fellas around here and they'll tell you I have no advice for anyone. I've got enough issues in my own garage to deal with. One thing I can tell from your pictures is I can tell, you are my kind of people. :cheers: Welcome, and hope you hang around. :thumb:
 
well, the time has come to tear into the bike, both all around, and the motor! here we go!

merry christmas to me!




can you tell we like our toys?


starting the teardown




air filters a wee bit dirty.....


gas tanks off


found out a subframe bolt was missing...scary :0


radiators and stuff off


put a new spark plug in when i bought the bike 3 years ago, this is the first time its been out since!


anddd the dome is off!


underneath...




inside the exhaust port (powervalve slightly closed)


the jug








top of the old piston, which was a vertex


side shot


now here im trying to figure out what happened..2 guesses. one is they lost a piston or skirt and it grooved the bottom of the case like that, or 2 is maybe lost a rod and grooved it? either way its not as bad as the pictures look, but i think ill have it just grinded down, and or smoothed out. its run for 3 years so its obviously not detrimental.




you can see some oil down in the crank


old reeds








intake port


took some more stuff off


pile of parts off the bike


sofar the plan is to keep tearing into it the next couple days, get the clutch and stuff done, maybe wheel bearings. then theres bars, carb cleaning, and im probably gonna clean, scrub, and paint touch up the frame. i didnt take close ups, but a lot of the discoloring is just dirt. then theres some spots with missing paint im gonna scrub out and use goo gone (dont know why that shit stops surface rust completely..)

also bringing my jug to my dads machinist to port and polish. although after looking at it im not even sure how much he can really do with it. lol but ill have him scrub hone and restore the cross hatch, which was still visible in some spots, but restoring the cross hatch is probably in my best interest.

pics and more info and progress to come!
 
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well, the time has come to tear into the bike, both all around, and the motor! here we go!

merry christmas to me!




can you tell we like our toys?


starting the teardown




air filters a wee bit dirty.....


gas tanks off


found out a subframe bolt was missing...scary :0


radiators and stuff off


put a new spark plug in when i bought the bike 3 years ago, this is the first time its been out since!


anddd the dome is off!


underneath...




inside the exhaust port (powervalve slightly closed)


the jug








top of the old piston, which was a vertex


side shot


now here im trying to figure out what happened..2 guesses. one is they lost a piston or skirt and it grooved the bottom of the case like that, or 2 is maybe lost a rod and grooved it? either way its not as bad as the pictures look, but i think ill have it just grinded down, and or smoothed out. its run for 3 years so its obviously not detrimental.




you can see some oil down in the crank


old reeds








intake port


took some more stuff off


pile of parts off the bike


sofar the plan is to keep tearing into it the next couple days, get the clutch and stuff done, maybe wheel bearings. then theres bars, carb cleaning, and im probably gonna clean, scrub, and paint touch up the frame. i didnt take close ups, but a lot of the discoloring is just dirt. then theres some spots with missing paint im gonna scrub out and use goo gone (dont know why that shit stops surface rust completely..)

also bringing my jug to my dads machinist to port and polish. although after looking at it im not even sure how much he can really do with it. lol but ill have him scrub hone and restore the cross hatch, which was still visible in some spots, but restoring the cross hatch is probably in my best interest.

pics and more info and progress to come!

Once again.....great pics, looks like a pretty good project for ya. After seeing your first couple posts, I don't spose you'll be shy bout sharing pics and updates, looking forward to it.
 
battle scars...and numerous missing bolts for plastics..hoses..stupid shit here and there. lol hopefully by the end of the day and 20$ later, ill have restored cross hatching, and a knife edge exhaust port on the jug!
 
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