2012 YZ 125 Build

[JohnF292]

picked up the bike in West Virginia new in 2013. I had some training prior to this bike so i had some skills. With that i just started with basics such as hour meter and suspension re-valve. here's how she sits now with 19 hours!

updated Nov. 2014 - 19 hours
-Renthal 49/50 tooth rear sprockets
-Get Real Racing Suspension Re-valve
-Hardline Hour/tach meter
-FMF Shorty silencer
-FMF Factory Fatty pipe
-Renthal twinwall blk 999 bend
-Arc Folding brake/clutch levers
-Jd jetted

The bike as of now has the 50t rear sprocket and its a little jumpy for me so i'm going to try the 49t. I had my friend give me a base line jetting for the pipes but i have the spooge so i will get around to a full re jet. She does need some stuff such as fork seals / oil, and tires. I would like to get some recommendations for these. I usually only do track riding. I'm aggressive when it comes to corners and I can usually clear all the jumps and some triples on the tracks, but I'm not scrubbing or whipping at all. I ride usually in upstate ny, long island ny, or nj. Mosrt of the ny spots are hard packed and rocky, while nj has softer tracks. not sure what tires i want. I usually stuck with the Michelin Star cross MH3. Want to try something new maybe.

 

[ossagp]

picked up the bike in West Virginia new in 2013. I had some training prior to this bike so i had some skills. With that i just started with basics such as hour meter and suspension re-valve. here's how she sits now with 19 hours!

updated Nov. 2014 - 19 hours
-Renthal 49/50 tooth rear sprockets
-Get Real Racing Suspension Re-valve
-Hardline Hour/tach meter
-FMF Shorty silencer
-FMF Factory Fatty pipe
-Renthal twinwall blk 999 bend
-Arc Folding brake/clutch levers
-Jd jetted

The bike as of now has the 50t rear sprocket and its a little jumpy for me so i'm going to try the 49t. I had my friend give me a base line jetting for the pipes but i have the spooge so i will get around to a full re jet. She does need some stuff such as fork seals / oil, and tires. I would like to get some recommendations for these. I usually only do track riding. I'm aggressive when it comes to corners and I can usually clear all the jumps and some triples on the tracks, but I'm not scrubbing or whipping at all. I ride usually in upstate ny, long island ny, or nj. Mosrt of the ny spots are hard packed and rocky, while nj has softer tracks. not sure what tires i want. I usually stuck with the Michelin Star cross MH3. Want to try something new maybe.

I see a spare set if wheels with sand tires on them I'm your future. Don't chase jetting until you set the float.

 

[JohnF292]

I see a spare set if wheels with sand tires on them I'm your future. Don't chase jetting until you set the float.

That would do me some good for when i go to north Carolina and long island. Any tire recommendations for sand and hard packs. When I'm home for thanksgiving ill try sort out the float and jetting. Any tips / links for the float test? do I need a special tool?

 

[ossagp]

I will do my best to help you sort out the float and the tool you need when I am in front of my PC. I can go on a pretty long time. The actual act us dimple and easy. For some reason yamaha chose to complicate it.

 

[JohnF292]

I will do my best to help you sort out the float and the tool you need when I am in front of my PC. I can go on a pretty long time. The actual act us dimple and easy. For some reason yamaha chose to complicate it.

Appreciate the help a lot!

 

[Mihylo33]

picked up the bike in West Virginia new in 2013. I had some training prior to this bike so i had some skills. With that i just started with basics such as hour meter and suspension re-valve. here's how she sits now with 19 hours!

updated Nov. 2014 - 19 hours
-Renthal 49/50 tooth rear sprockets
-Get Real Racing Suspension Re-valve
-Hardline Hour/tach meter
-FMF Shorty silencer
-FMF Factory Fatty pipe
-Renthal twinwall blk 999 bend
-Arc Folding brake/clutch levers
-Jd jetted

The bike as of now has the 50t rear sprocket and its a little jumpy for me so i'm going to try the 49t. I had my friend give me a base line jetting for the pipes but i have the spooge so i will get around to a full re jet. She does need some stuff such as fork seals / oil, and tires. I would like to get some recommendations for these. I usually only do track riding. I'm aggressive when it comes to corners and I can usually clear all the jumps and some triples on the tracks, but I'm not scrubbing or whipping at all. I ride usually in upstate ny, long island ny, or nj. Mosrt of the ny spots are hard packed and rocky, while nj has softer tracks. not sure what tires i want. I usually stuck with the Michelin Star cross MH3. Want to try something new maybe.

NJ tracks like E-town... I'm running the Maxxis IT. Love that tire, but a lot of guys are running the MX51s around here as well. I did the JD jet kit and the only really good thing about them is the needles are like works of art. I still end up jetting all the time to achieve what I want.
suspension.... Factory Connection. No other tuner touches my bike other than FC. Yeah, they're that good.

48-49 teeth will be good for these types of tracks.

oil: pick a brand and stick with it. You'll never go wrong with Yammalube and don't fall for the hype from some of these other oil companies. 32:1 and only 32:1 is all that bike should ever see. Same goes for the trans... Yammi 10w40 is what this bike craves...
Good luck.

 

[ossagp]

The float as you probably know controls the fuel level in the carburetor. Contrary to what a lot of people think, that level affects your overall jetting. It can affect it a lot. The rigs you used to see winning races on TV when they all had carburetors got theirs set before each event, and maybe even reset during the event.

You should get a yamaha shop manual, the factory variety. It will help you more than anything else if you use it and follow it. It will give you the setting for the float. The problem with yamaha from a DIYer's standpoint is that they give it to you the way a tuner would like it and leave it to you to find the most expedient way to set it. Yamaha's way demands that you buy a tool or build one to check the ACTUAL level, as opposed to just giving you a setting you can measure with your calipers. Their way turns out to be unhandy at first.

The tool is really just a float bowl plug that allows you to hold the attached clear tubing up to the side of the carburetor and see where that fuel level comes. they give a suggested range for that fuel level (more on that in a minute). The "tool" is really simple to make off of your existing float plug. you simply get a small piece of fuel line and a barbed connector. appropriate sized drill bit, and either solder or epoxy. drill the bottom of the bowl and install the little hose barb. now you can check the fuel level. you can leave the tubing on their and route it up to your air box like so many offroaders do. it gives an extra "volume" so that water that got in the fule can collect,
you can see it and dump it. and constantly see if your float level is rising.

The drawback to this method is that on the initial settings you have to look, determine that your level is off, then take the bowl back off, bend the tab on the float itself (the one that contacts the float needle) and move it one way or the other to affect the change. then you put it back on and repeat the checking process to see if you went too far or not enough. the specs will show a range from the gasket surface where the bowl and carb body meet. something like 5.3 mm to 5.8 mm. most think that anything in that range is acceptable. in a way it is. That wasn't the way the factory mechanics use an "acceptable range". to them it is a guide. past 5.8 may lower the level to where a stock bike may actually starve out and run lean etc. something under 5.3 may make it flood easily in corners. the tuner would find a setting for their purpose, jet the bike at that setting and keep returning it to that setting. Some had different levels they preferred for specific riders or tracks. For offroad I like to keep the fuel level low. it can get you more miles out of a tank. Supercross tuners liked higher float levels. If you ever attended a supercross race where the best of the best were you saw bikes taking a real pounding over whoops, jumps and rythm sections. The tuners preferred the higher levels due to a lower one allowing the carburetor to have the fuel bounced badly enough that the jets were exposed to air and not fuel. That leads to the bike losing power worse than a floodout situation. you could see the fuel running out the overflows and onto the cases if you got to see a bike that just came off the track lots of times. you could also see and hear the riders doing some clutch and rev work too. For mx I prefer something towards the higher end of the range, and developing my jetting from there. Keep notes. Keep notes. Keep notes.

Let me know when you have the plug modified for checking the level.

FYI the float plugs i have modified have all been done by using fuel barbs from model airplane boat places. sometimes I have used the fuel line they use too. just test it to make sure it works with gas or get some intended for carb vents.