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06 Yz125 - setting up for old guy novice

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A while back we as a family decided to try to the dirt thing with atv's and I stuck with a bike. After a couple of 4 strokes (yz 426 - first bike I had with a good suspension and later a crf450) I ended up with a 95 Cr125 and really liked the low weight, but it needed some fixing (fork seal leak, so why not update to newer forks? then there is the shock and on and on). Fortunately I found a deal on an 06 yz125 which short circuited my attempt to put way too many dollars into the CR125. Now I have the newest dirt bike I've ever owned and I'm trying to get more used to it. 

First off the power of these 125's is incredible and I'm trying to tame it down while I learn. It has an athena 144 kit.  Before riding it, I installed a 7oz flywheel weight. The bike definitely didn't rev up or down as fast as the CR125 and I'm not sure I liked it going into a corner and I'm going to have to pull it to feel the difference. It has an FMF pipe and short silencer that I think is good for low end, but maybe low end means harder power hit at lower rpm (hard hits are hard to control right now). It's a 2T, but I'm willing to trade power for a smoother torque curve until I have better clutch and throttle control. Some would suggest going back to 4T, but the low weight of the bike trumps everything else. I do wonder if any of the 'woods' pipes flatten out the torque curve more?

On the suspension I set the rear sag for me and it seems to handle ok, but it's a taller bike than the CR125 and I have lots of settings to fool with. I was thinking about a lowering link and different shock spring, but after talking to a salesguy, I'm pretty sure I do not have a stock spring since it took only a little adjustment to get 4" of sag with my 195lbs. I probably need to hold off on linkage changes until I figure out what I have. The bike was raced previously with a pretty small rider so I'm not quite sure what I have for springs (or why it would work for my weight). I probably need to pull the fork springs to see what I have - they should be too light for me, but they don't feel like it (it's even hard to strap down for transport). 

So if any 56 year old novices have one of these and have the perfect learning setup, I'd love to see it. 

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OK, I was reading your post and started thinking, "If I had the exact bike you have, what would I honestly do"?

 

  1. I would get a manual so you will have a reference on stock settings etc...
  2. Go over the bike and make sure everything is lubed properly and worn parts are replaced.
  3. Get the jetting dialed in (it could be fine, make sure) Check the reeds (see item #2).
  4. If you are serious about keeping the bike and getting it setup properly for you, find a good reputable suspension specialist to get the suspension dialed in properly for you and the type of riding you do. This is probably the best money you can spend on a bike!
  5. Check out the forum posts for owners that have the 144 kit. That way, you can specific info on the 144 engine.

That is what I would do. Before you check everything out and get it in good operating condition, you might be chasing possible problems.

I think I would prefer a stock engine myself, but that's just me.  

Good luck with your project. Enjoy the ride!

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There was a recall on the 2006 model YZ125 to update a part called the 'shift stopper', make sure that was done.

 

With you at 195lbs + gear and, with that oversized fuel tank filled up, 

if they already haven't been replaced, stiffer fork springs will likely be required.

 

At 4" / 100mm race sag, what is the free sag measurement?  (weight of bike only, fuel fill up to 1/2 tank)

If within 20 to 35mm, (3/4" to 1-3/8") you then have the proper shock spring rate. (the linkage must not bind for this to be accurate)

 

A stock length silencer will broaden the power,

in most cases shorties add some additional 'hit' but fall off the pipe sooner, perhaps even more so on a 144.

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You don't need to do much to a YZ 125 to have fun.  I agree totally with dmrogers above:

a. basic maintenance

b. suspension--at a minimum springs for your weight.  YZ 125s are particularly sensitive to spring rate and how if affects cornering (I own two myself).

c. if the opportunity comes up to go back to a stock top-end (maybe when the 144 wears out?) I would do it.  The 05 and later stock engines are actually very good for novices, easy to jet, and reliable as a brick.

d. Check the shift stopper.  The 06 definitely comes with the ball bearing model, and needs the update.

Finally, I would resist adding things to "tame" the 125 (FWWs, O-ring chains, pipe combinations, big bores, etc).  The yamaha engineers knew what they were doing, and they made the best 125 engine ever, until KTM upped the ante in 2016.  The better (and cheaper!) option is to accept the 125 for what it is, learn to ride the power, and enjoy the fun.  You are not too old.  I am 55 and I think about riding my YZ 125s all week, while my 250 just sits and collects dust.

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Thanks for the replies. My concern is about what defines a "good" engine. My thought is that I would be "de-engineering" the 125 motor for a while to make it a little easier to ride. I thought the direction for "good" is mainly more power and secondly try to spread it out over a few more rpm. Most of my experience is road bikes and some road racing (until I had to get life insurance) and the best bikes almost always had the widest powerband and were often called boring by folks not racing the bike. I suppose the 4T bikes bring that to the dirt, but also added weight. I liked the smooth power of the 426 and 450, but the I like low weight better. 

I had an interesting experience with a super narrow powerband the other day. I wanted to top off my fuel and dumped enough klotz for 1/2 gallon in the tank followed by gas. Since there was already gas in the tank I assumed it would mix. Wrong but I think a side of the tank had less fuel than I thought. The klotz went right to the bottom and I was running on oil. After clearing the carb I got it running but it was only running with the choke. That made the powerband worse than ever and I got launched off a jump. It was fun (after my heart stopped pounding), but unintended. I got back to running without choke and it ran normally again. So I think I've tested the far end of a narrow power band now (3 to 21hp in 0.5 degrees of throttle)

The suspension is sort of an enigma right now since it looks like the free sag is ok as well. I really don't like the large tank at this point and plan to go back to stock. I'm trying to get as much riding in as possible now, so I probably won't tear it down yet. I'll try the compression/rebound settings to see how that feels. I probably will try to find a stock pipe and silencer in hopes it would smooth the engine out more so I can focus a little more on suspension (but there's the 144 kit?). We farm so maybe when harvest starts I'll pull the forks and shock and have it rebuilt and setup for me. 

Overall, it looks like the bike was taken care of pretty well in it's former life. It had an obviously worn chain and sprockets when I got it but that was probably from the most recent owner doing not so much maintenance (15 yr old, nice guy, but probably didn't know about chain lube). The engine oil looked good with only a hint of shiny stuff (probably hadn't been changed since it's racing owner). I'll have to research the shift stopper to make sure it was done.

At a minimum it's a great starting point for basic changes like springs and fork valving instead of grafting newer parts on an older bike (my cr125 plan). I plan to call the suspension shop that may have worked on it (or at least sold the stickers) and see if they have a record by vin number. Not sure these guys keep records though. 

 

thanks

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The 05 and later YZ 125 probably has about the smoothest 125 powerband ever--crisp even on the bottom with a good mid and high.  I actually prefer the more "traditional" powerband of my 03 yz 125 over my 06, but I spend almost all my time riding 125s these days, so I'm really used to keeping the revs up.  The 144 kits that I have ridden offer a really strong mid range surge, but it seems like the top is chopped.  Some guys love them, but I just kind of like the old-school 125s!

If you need a chain and sprockets, my suggestion would be to go with an RK 520H chain (yellow box).  It is a regular chain but is really quite durable if you lube it over the course of the day's ride.  I've tried a lot of chains on 125s, and this seems to be the best combo of price and durability.  Just keep checking ebay and amazon, as it will go on sale for silly cheap.  Just buy a 120 link and cut it to your sprockets.  I would avoid ring chains (X and O) as they dull the response of the engine with the additional drag.   For sprockets, at one time Outlaw racing was offering a lightweight steel rear sprocket (made in Germany!) that was great, but I don't think it is available now.  I've been using the JT steel sprockets on my bikes lately.  

Money on suspension is the best money you can spend.  Make sure your tuner checks your spring rate, as you never know what your are going to get with a used bike.  A friend of mine bought a 250f, and we could not get it to turn like we felt it should.  Our tuner measure the spring rates, and it turned out the bike had the stock rear spring, but the forks were like 4 steps up from stock!  I have had good luck with the major players (e.g., Factory Connection) as well as local or regional guys.  My current favorite is SoPro in Tennessee.  He does killer suspension on YZ 125s, and while no suspension guy is cheap, at least his prices are more reasonable than FC or the other big boys.  He is great to work with.  

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I have an EG144 and putting a 1 larger tooth front sprocket took some of that snappiness that was causing me grief in the form of wheel spin. Also maybe consider a 6oz flywheel weight to help luggability in low revs. Once the revs pick up its effect is not really as noticeable. If you dont like it you can take it off and sell it on ebay

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54 here and I also have a 2006 yz125 (and also a 2011 yz250). I put an Eric Gorr 144 kit on it a few years back, and I love this bike! As others said above, the 2005+ yz125 is already the smoothest, broadest powerband 125 ever made. The 144 kit make it even broader and smoother (at least the EG one. Never tried Athena). As the previous poster said, going up one tooth on the front sprocket (14 tooth) is a GREAT idea with the 144 because it has enough torque to pull the taller gear ratios and the shift points become perfect. I recommend getting the factory service manual (downloadable for free) and going over the entire bike. Be suspicious of anything that is not OEM. The factory pipe and silencer are probably the best possible choice for a 144. Jetting is essential of course. I could go on, but there are sooooo many excellent 144 threads already that outline what works best. Good luck!

PS. The pic looks like a stock spring. If so, it is too light for you. I am also 195 and to get proper sag I think I ended up with a 5.1 or 5.3. I'll have to check. I believe stock is 4.7. If you tighten the 4.7 enough to achieve the 100 race sag you will be near 0 on the free sag, which is not good for handling at all. However, you said free sag seemed ok, so maybe someone already increased the spring. The original is titanium. See if a magnet sticks to it.

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Thanks for the tip on the spring. I'll check it with a magnet tomorrow. I need to call fast lap and see if they have any info on the bike. The kid that owned was oddly smart enough not to say much about the bike except for the tidbit he knew (really rare these days on FB ads - lots of cobbled together bikes with somewhat cobbled ownership). I was thinking it was mx raced, but the oversize tank says some sort of enduro, yet the 19" rear is not the cool thing in woods/enduro. I'm hoping to get out to our riding spot pretty soon. The kids are back in school so I'm not sure the 5pm to dark rides will keep going and I'm not sure I'm ready to go solo - it's a pretty remote place and I have good life insurance. The family would be sure to start looking for me in a week or so, but on the upside I might have a nice funeral (so I got that going for me.... which is nice). 

I think I'll try to find a stock pipe and I have a 14T front sprocket already ordered. What rear sprocket do you guys run? (I have a 48 and 52 now)

thanks

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13/48 (3.69) is the original final drive for that bike, so going to a 14/52 would pretty much be equivalent :

 

13/48 = 3.69

14/52 = 3.71

 

13/52 = 4.00 which would be quite steep 

(actually what I'm running on my CRF250X but it has a wide-ratio gearbox)

 

13/48-49-50 is popular for motocross (125)

Edited by mlatour

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2 hours ago, harmetp said:

 

I think I'll try to find a stock pipe and I have a 14T front sprocket already ordered. What rear sprocket do you guys run? (I have a 48 and 52 now)

thanks

I am running the stock rear sprocket, so the combo is 14/48. It seems perfect for mx, not sure about trails and such.

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Well, I got out to ride some this weekend and removed the 7oz FWW after a few laps and it might have made it a little easier to run since it the motor slowed quicker giving me a hair more engine braking (as if a 2T has that much anyway). 

I thought about lowering the forks 5mm to see what happens but turned out not to enough tools to do it right (loosening the clamps didn't result in any leg wanting to move). So it's a home project.

I thought I had an aftermarket shock spring since it seems like the race sag and free sag are in the ballpark, but it's a not a steel spring and looks like it might be the oem spring. I have the lock rings about half way up the shock body to get the race sag - does that seem about right? I realize there are different spring lengths available also which would affect this position. 

I did get in touch with the suspension tuner for the bike (Fastlap) and the guy (steve) thought he knew which bike I had since he didn't do many 125's and my bike has the athena which this rider had done also. Apparently a pro level woods rider that weighed about the same as me. That started to make sense until I looked at the spring color again and tried a magnet. I suppose the bike has gone through several owners since the pro guy (parts sold/swapped, etc). The chain and front sprocket were completely worn out so I imagine the pro riders ownership was in the distant past. So, it sounds like I didn't get much closer to understanding what I have. Steve at fastlap offered to make me a deal on suspension service and I think I'll take him up on it this fall. 

I do have a $100 unused oem pipe and silencer coming to further try to smooth the engine out. Seems like if I take it pretty slow I have pretty good throttle control but once I start going faster and actually hit a small jump my tendency is to hang on too tight the bars and move the throttle a tiny bit - usually a tiny bit too much and things get out of shape. It hasn't thrown me to the ground yet though. A hair more progressiveness should help until I go faster.

On the subject of faster - this thing is fast. I'm riding on a tiny tight track with 180 degree turns and in about 10 feet I can be way to hot for the turn. I have it geared with a 13/52 which is likely the wrong direction and I have a 14T to go with the 48T I already have to try what you guys have recommended. The 426 and crf450 (and especially the bone stock crf250) I've ridden didn't make this sort of speed as quickly. I suppose it's the 50lbs lighter and peak power that isn't that much less than the 4T bikes. 

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I just found a set of ohlins forks that would fit my yz125 for too much money. However, I have ohlins forks and shock on ducati 1198sp and it's amazing how well they work - great handling while still not making every little bump (or bigger bump) knock the bike (and me) around. Seems like a neat idea, but putting $2100 into a $1250 yz125 doesn't seem like a great idea. I'd probably still need to have the forks and springs set up for me. Anyone think ohlins is way better than anything else?

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Many owners of other makes/models are actually envious of the KYB suspension on 06+ YZ125's, 

in stock form it's already got one of the best fork & shock out there.

 

But like anything else it does require servicing to maintain it's best performance and that's something many neglect.

 

A few hundred dollars invested in new oil, seals, bushings, nitrogen recharge

and if required spring rates to match your weight & skill level 

could be more beneficial than bolting on those Ohlins components that would still require some tuning.

Edited by mlatour

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Suspension is what you want to spend money on, but it's much better to work with what you have.  I personally believe that any Japanese suspension from the late 90's on can be made to work spectacularly well when you have a tuner that know's what he's doing.  How do you find a tuner that know's what he's doing?  Check out the local race scene and maybe bum a ride on a few examples of his work.  Or you can always use one of the national brands that has been around forever.  I've had great results with Factory Connection as well as local tuners.  

Liked noted above, if you buy the other suspension kit, it's going to need the same work (seals, springs, oil yada yada) as any other suspension, but it's probably going to cost even more because of the name.  

Finally, the 06 and later YZ suspension is sort of legendary, with people spending lots of time and money acquiring it to put on their bikes (even seen it on some KTMs!).  I actually prefer my tuned 03 suspension to my tuned 06 suspension, but both are great. 

Edited by rpt50

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Thanks again. I was looking to see if I could get another set of of 06 forks and a shock to send away to the fastlap people and that's when I saw the ohlins kit. 

The oem exhaust should be here this week (I hope) and maybe it's time to rethink the rear spring since I'm not seeing many aftermarket titanium springs (I may just have a stock spring). I'm going to check the free sag one more time today just to make sure. 

I wish I had a better idea of the dynamics taking place. On the yz426 at a big mx track it was amazing that I barely noticed the bike leaving the ground and if I didn't jam on the front brake, it when through corners pretty easy. If it wasn't for hot starting the stupid thing, I should of just kept it. The crf450 (surprise trade deal for remainder of crashed F350 truck) with a rekluse was easier all around, but I never got back to the big mx track before killing it in 4 ft of water. On the other hand, the 125 is light, but seems stiff. Hitting rocks (4" diameter) tends to upset it more than I expect. It doesn't feel as confidence inspiring as the CR125 at this point. I'm pretty sure I'm just too far off on suspension for my skill level (skill seems to make up for about any suspension at times). 

Thanks for the responses. I'll post what happens next.

 

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14 hours ago, harmetp said:

 Anyone think ohlins is way better than anything else?

Stick with the original KYB and have them revalved for your weight and style. (I, too, have had great results from Factory Connection). The KYB system on Yamaha is the best of the best, and *especially* on the 125, which is often described as the best handling mx bike in the world.

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Update, went riding again but did a little "development work" at home first. I started by installing a stock silencer on the aftermarket exhaust (can't remember if it's gnarly or fatty - the label is covered by a crash guard). This seemed to smooth out the power somewhat and softened the hit at higher rpm. Next was to install a 14T with my 52T rear (which brings me back to near oem ratio) and it seemed helpful. I can actually put around without clutching and revving. I have an oem exhaust (from a 2016) to try next, but I got the chance to go riding so it's on hold.

So, the motor is more forgiving, but now the suspension is starting to show it's short comings. I had thought I had a different shock spring in back, but this one is titanium and while I was able to get 4" of race sag, the free sag is really only 1 1/4" so it's likely the oem spring for 130lb riders. I'm guessing the front is equally wrong for my weight and I have ordered the correct spring (using the racetech calculator). it should be here this week and before riding again i'll change the springs and exhaust and see where I am. 

I also still have the 7oz FWW off the bike, but it might get a another try after the springs are installed

I enjoy some of the tuning/tinkering with the bike, but so far it's not as fun as the 426 or 450 I had. After thinking about it some, the 426 made me feel like Ricky Johnson only much slower and on a yamaha. Going over jumps had almost no drama. Now, I like the light weight of the 125, but going over a bump has a certain randomness to it (will the tire spin up a little and send me a little sideways, will the attitude of the bike be predictable?). Also going into turns seems more squirrely than I'm expecting. I have not taken the 125 to the larger track where I rode the 426, so the tightness of where we ride now certainly has an effect. 

In the end I'm just another older guy looking for a bike that fits like a glove and makes riding a lot of fun. Could be that I roll back into the 4T world, but that might be put on hold if I can get the suspension setup differently and it works. The old guy dream bike is typically the ktm 450 with the magic button. I would guess that in stock trim, it's not far off for a guy my size and would take much work to get it dialed in. It's still weighs more and certainly costs more so I'm pushing on to hopefully create my perfect yz144 Old guy bike

Thanks

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