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Picking up my first 2 stroke 125

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Hey guys

 

So I decided to go back to fundamentals and also wanted a back up bike so I picked up a 2016 YZ125, I currently ride a YZ250F and all 4 strokes are all I know as far as riding (yes I know big no no)  Ive been riding about 3 years now give or take, C class old vet rider. Anyways besides the usual creature comforts (bars, levers, new air filter, etc.) what do you guys recommend to make the bike manageable for a newb stroker moving to a smoker, lol. I've heard of fly wheel weights, reeds, etc. Dont want to spend too much, but dont want to kill the darn thing in every turn either and want her purring. Also what are you guys running for premix and ratios? Thanks for all the help in advance. Im pretty excited, many of my friends have said I'll want to sell my 250F after being on the new bike. 

 

Zach

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First off congrats on the new bike! Two years ago I bought a new 2014 YZ125 and modded it before even riding it... Don't make the same mistake I made, ride the bike and decide for yourself what Mod's you think you need.

For instance I listen to everyone about what the best gearing was only to arrive back to stock on the 3rd try. V-Force reed was a waste of money also. And don't run a shorty silencer on the stock expansion chamber, it kills all the over rev in my experience.

The Mod's I would suggest if you want more responsive, easier to ride power would be porting, head Mod's and exhaust that the porting tuner would suggest to compliment his work. That's what I have done to mine and I've had people ride it that were blown away at how much faster my bike is than there 125.

I've got Enzo tuned suspension but to be honest it's not light years better than stock. I will be sending it back over the winter to see if they can get it a little closer to where I want to be.

Hope this helps, what I'm trying to say is that it's hard to improve on this bike. Yamaha has it dialed

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What kind of tracks do you ride? Adding a tooth or two to the rear sprocket might make her sing more easily. Otherwise, they're great bikes and don't require much work to go fast. Personally I use a braided front brake line on all my YZ's.

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What kind of tracks do you ride? Adding a tooth or two to the rear sprocket might make her sing more easily. Otherwise, they're great bikes and don't require much work to go fast. Personally I use a braided front brake line on all my YZ's.

 

One track is hard packed the other sandy with mulch and dirt mixed in. 

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more responsive, easier to ride power would be porting, head Mod's and exhaust that the porting tuner would suggest 

bingo

 

And big bores. Your in the Vet class bro. You deserve a big bore.

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As the owner of a 2010 YZ125 I'd suggest to keep the engine, pipe and reeds all stock,

while not absolutely necessary but if you can find the slightly shorter 2006-2010 stock OEM silencer buy one,

don't be tempted to install an aftermarket shorty on the stock expansion chamber headpipe.

 

Not saying that some bolt-ons, porting or even a 144 big bore aren't worth it in the never ending quest for more power,

it's just that the stock engine configuration is a well proven package and easy to fine-tune by simply following

the jetting guidelines in your service manual, an important consideration since this is your first 2-stroke.

 

In a 2-stroke proper jetting is everything;

-too rich and your engine stutters, fouls plugs, leaks un-burned oil, saturates the silencer's packing, doesn't overrev well

-too lean and you engine lacks throttle response, bogs badly etc. If ran excesively lean you'll risk seizing / damaging it

But by taking the time to fine-tune it close to 'perfect' to match ambiant temperature & conditions, you are always rewarded with a strong crisp running race machine.

 

Buy a few extra pilot and main jets (genuine Mikuni/OEM) Figure doing a jet change / small adjustment for about every 15°F rise or drop in ambiant temps to keep the engine performing optimaly.

Don't be intimidated, after a while you'll get the 'feel' if the engine runs rich or lean, you won't hesitate twice in doing a jet change so the engine always runs it's best. It only takes 15 minutes to do.

Always premix at 32:1, Amsoil Interceptor is a good clean burning choice, avoid 'racing' type oils if you are not yet running WOT most of the time.

Never less than 91 R+M/2 octane (95 RON) ethanol-free premium pump gasoline, perhaps mix in 25% race fuel if you want an extra safety margin to prevent detonation.

 

When doing your first top end maintenance, measure the combustion chamber's squish height and have it corrected if necessary,

that will reduce octane requirements and make your engine run even crisper.

Your new engine gets about 180-185psi on it's new top end. No matter after how many hours, when it drops to about 155-160psi figure it's due for a refresh.

 

If you weigh more than 160lbs. or ride really tight tracks, add a tooth to the rear sprocket.

I have a 9oz flywheel weight on mine, it helps somewhat to avoid stalling in really tight corners.

As Sheriff245 mentioned, a steel braided front brake line makes a nice improvement in brake 'feel'.

 

Until you master the ability of riding your YZ125 with the throttle absolutely pinned all the way around the track,

having the suspension dialed in for your weight (spring rates) and skill level (valving) will matter more than any engine mods.

Edited by mlatour
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I've found (riding one in the woods) that number one is to get your suspension set how you like it.  This may involve more than clickers.  

 

Number two is to ride it like a hyperactive teenager!  The clutch only really works when your into the meaty part of the powerband and the engine is really singing!

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In my opinion, the greatest mod I ever made to my 2006 yz125 was making it an Eric Gorr 144. The power is better everywhere, the top end lasts much longer, it's still the same weight, and it is even more fun to ride. I left everything else stock except the suspension of course, which was revalved by FC and spring for my weight (185). 5.1 shock spring, .43 forks.

 

Unless you are considering the 144 I wouldn't touch a thing (other than jetting of course). Definitely keep the OEM pipe.

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I say keep it stock and ride the thing first stock jetting is really close for most conditions don't worry about it too much right now. Only changes you should be worried about are like your favorite bars n grips and tires. Master riding it first before major changes.

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Thanks guys for all the input. I agree, stock she will be for now, minus my bars, grips, etc. Any way of breaking her in, guess similar to a 4 stroke just minus all the oil changes. lol. 

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Thanks guys for all the input. I agree, stock she will be for now, minus my bars, grips, etc. Any way of breaking her in, guess similar to a 4 stroke just minus all the oil changes. lol.

I just do a few heat cycles.. Then let it rip.

I also drained the fuel the dealer put in to run my own mix.

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I'm in my mid 50s and all I ride now are 125 smokers (I have two yz 125s).  My 250 smoker is an expensive rack for drying my riding gear, and it has been ridden exactly twice since May of 2015.  I take my YZ 125s out to play every weekend.  

 

My advice would be as follows:

 

1. Leave the motor stock, and run 32:1.  It can't be any more fun than it is.  I have been largely unimpressed with the 144 kitted bikes I have ridden.  They just don't feel "free revving" like the stock motor. There is just a "blob" of power and then it is time to shift.   I also wouldn't even bother with a pipe, unless you smash the stocker.  One of mine has a Pro Circuit pipe and the other has the stock pipe.  If there is a difference it is certainly nothing to write home about.  Also, don't let a FWW come near the bike. I always put them on 250s, but you want to be way up in the rpm range on a 125.  It's not going to stall if you have the rpms where they are supposed to be!

 

2. Jetting will be very close with stock jetting at 32:1.  If you are riding in sand, leave it alone.  Maybe a tad leaner (optional half step needle) if no sand.

 

3. If you are riding offroad, get the suspension done.  It will be the best money you have ever spent.

 

4. Where ever you ride, it is essential to have the bike sprung for your weight.  The handling is very poor if you are over 170lbs and trying to ride stock springs.  

 

The mods you need for the bike are really very little. My bikes are revalved/resprung for offroad and have the usual offroad protection (skid plate, hand guards, big tank for races), but are otherwise stock. What you really need to mod is your riding style.  You really need to use first gear.  When you want to upshift, don't do it.  When you think you need to downshift, downshift twice.  Keep that motor spinning and keep that clutch slipping!  You are not going to believe how much fun the bike can be.  Get your 250f ready to be a rack for drying your riding gear.

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Suspension is the always the best way to spend money first. That thing will probably be dialed right away, as far as engine package is concerned. But to be 100% honest, i don't ride other peoples bikes because I know the suspension is not for me. 

 

Always glad to see suspension mods to be #1

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I have a 2009 YZ125 that I bought brand new.  Kept it completely stock for 4 years.  Never changed the jetting, or suspension (~150lbs).  Fastest, funnest 125 I've ever ridden, and my friends agree.  When I rebuilt I went up a tooth in the back, FMF fatty with shorty silencer, and now I'm able to carry 3rd gear in places where previously I'd be ringing it's neck in second.  Super happy with the extra tooth, fatty + shorty combo.  I ride some trails (more open than tight) and motocross style tracks.  I could tell a pretty big difference with the combo listed above, much easier to keep on the pipe in 3rd, which is where it fell off some with the stock setup.  Extra pull in the crucial gears, and really no loss of top end.  Like others have said....excellent bike from the factory that requires nothing but the willingness to ride it hard.  If you're over 175lbs, you may need the suspension tweeked.   I always run 32:1 Amsoil Dominator.  Minor upgrades I really enjoy are Renthal Kevlar grips and +10mm wider pegs from a newer YZ 4-stroke.  Enjoy and welcome to the smoker brotherhood!!

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Like has previously stated, don't do the mods until you feel you want them. At least other than guards. For instance, I am a woods rider and do not want or use a flywheel weight. If think it would take to feel that I love about the bike. Some love them. It's basically a matter of preference. If you don't stall much, you may not want one.

Edited by The Hedgehog

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