HowTo // 2014 Yamaha TTR125 Carb Swap

HowTo // 2014 Yamaha TTR125 Carb Swap

If you are reading this post, then you’ve probably found out that the TTR125’s have a major flaw in the choke cable design! And yes, Yamaha STILL hasn’t fixed it!

Stock Carb Problem

The problem stems from the choke cable slide in the carb has an O-ring that becomes corroded, swells up and then the slide seizes.  How it’s noticed, is you go to pull the carb plunger at the handlebar and it either won’t engage or disengage… then you end up breaking the plunger assembly. And like most, purchase a new choke cable then try to replace it only to find out the choke slide is stuck… stuck real good!

Solution

Your options are to have the dealer fix it, probably replacing the stock carb or the better solution that fixes the problem forever, is a carb swap! The carb that I’ve chosen for the job is the Mikuni VM24 from Sudco International, Part # MI 001.018 which cost me $120 plus 8.35 for main/pilot jet. This carb has the choke plunger right on the carb, no silly cable!

I contacted Jonathan at Sudco and he knew exactly what I needed for the TTR-125, he even knew the jets that I needed!

On the 2014 TTR-125 it is equipped with a dual throttle cable so this has to be removed and replaced with a 2007 TTR-125 throttle.

2014 TTR-125 Dual Throttle body:

I’ve got the parts list I used below…

Parts List

Carburetor

Mikuni VM24 from Sudco International, Part # MI 001.018

Jets

OEM Parts

  • 1B2-F6282-00
  • 5L9-F6243-00
  • 5X2-2628H-01
  • 5X2-26281-00
  • 5HP-26311-00
  • 5DG-14106-00
  • Longer Fuel line (I used some Tusk Fuel Line 1/4″x3′ Black)

You will also need a small E-clip for the single throttle cable modification needed. I got these from AutoZone…

E-clip I used:

Stock Carb(Right) vs Mikuni Carb(Left)

Here you can see the stock choke cable is seized up in the carb…

The Swap!

I’m going to briefly describe the steps I took to swap the carbs, there’s nothing real hard about this but I will point out a few things you should know.

Remove the old carb!

With that out the way, remove the stock throttle body as well. Now is a good time to put some new grips on the bike to. Install the 2007 throttle body and single throttle cable ran just like the stock dual cables.

New Carb!

Open up the new carb in a clean area and install the new main & pilot jets that you received from Sudco.

Twist off the top cap and remove the throttle slide that the needle is attached to. This is where a bit of modification is needed. The throttle guide will not screw into the top cap so we will drill a hole into the cap and use the small E-clip to secure it. I believe the drill bit I used was 9/32″ bit, here’s a photo of the drill bit and the throttle slide & E-clip installed on the top cap. BE SURE TO CLEAN ANY METAL SHAVINGS OFF OF THE CAP!!! Use a file or dremel but do not leave any metal that could fall into the carb!

Installed guide & dust cover:

E-clip installed. Using a pair of needle nose pliers the clip slide on with a bit of force:

Here’s the needle position I’m running.. so far so good!

UPDATE: I’ve had to move the needle to the MIDDLE setting. If your bike tends to cutout, not bog, at low speed/low gear, then move the needle clip up.

Now its time to slide the throttle cable thru the carb top cap & attach the slide/needle…

Install the Mikuni!

Install the carb back on the bike, exactly like the stock carb was installed. Notice the hose clap on the cylinder side, I had to remove the chrome spacer that was on the host clamp so it would secure tighter.

Be sure to level up the carb as good as you can. You will need a longer piece of fuel line to run to this carb as it sits differently AND the fuel intake is NOT slanted nicely like the stock. But this has not caused any issues.

With everything back together… turn on the fuel, turn the key, hit the magic button and BOOM!  Mine fired up FIRST TIME!!  I had to do a little adjustment on the air screw & idle but not too much. We have ridden 4 hard days of trails on this carb with no issues. I plan on pulling the carb out before the next ride and give it a good cleaning just to be sure no particles/dirt are present.

Final Thoughts

This was a pretty inexpensive & easy mod that not only fixed the dreaded choke cable issue, but also runs a lot better than the stock carb. I’ve removed the air snorkel on the airbox and run a No Toil air filter.

I highly recommend this mod as it has really taken the worry out of this bike and it runs very well. Be sure to jet it right for your elevation and I’m sure you will have the same results. BRAP!

Basher Approved!

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7 Comments
  • Jim Pollock
    Posted at 22:30h, 26 August Reply

    My son has a 2012 with that same double cable carb. Having similar bogging issue and considering the upgrade, but would like to try adjusting the needle but can’t figure out how to get the slide out with that linkage. Any ideas?

    • Basher
      Posted at 20:58h, 03 September Reply

      Hey Jim… I never tried adjusting the stock carb needle.. due to the choke issue as well as bogging… I went straight for the swap. It’s been very good, just after the first good ride on the new carb I took the carb off and cleaned it good again, jets and all. I’ve also moved the needle a couple times to find the sweet spot. I’m currently running 3rd notch up from the bottom.

      Good luck!

    • Chris V
      Posted at 06:00h, 06 October Reply

      Jim: My son’s 2012 TTR-50 has the same dual throttle cable setup and I can’t figure out how to remove it either. To clean his pilot jet I just left the throttle cables attached and removed the intake, airbox connection, choke & carb heater connections, turned the carb sideways (while still attached to the throttle cables) and then had pretty easy access to the float bowl and jets. I’ve been searching all over unsuccessfully but would REALLY like to know what the correct procedure is for removing the throttle connections.

  • Matthew
    Posted at 18:04h, 03 November Reply

    What elevation are you at? I did the VM24 swap and am running a 17.5 pilot. It starts up and idles perfectly. The carb came with a 210 Main which was way too rich and now I’m trying everything from an 85 to a 105 main and the bike seems to cut out past half throttle. 155 Main seems big, but you sound like you’re having good luck with it. I’m at 400 to 700ft above sea level average humidity 30% to 60%. Is that close to your location?

    • Basher
      Posted at 21:43h, 20 November Reply

      Hey Matthew…. I’m at 600′ to 700′.. our property we ride at is 764′ elevataion.. in Missouri so lots of humidity. My boy’s did the same thing until I moved the needle to the middle setting, and now it runs very good. One time I did have to clean the carb out again but so far it’s been very good.. way better than the stock every was!

  • Sean wilt
    Posted at 06:04h, 03 January Reply

    So what do you do about the extra lines on the mv24 carb I’m sucking air in the one and the bike is still getting to much fuel and bogs out and my needle is on the top setting I bought it on amazon they said it was ready and did not need to be rejected

    • Basher
      Posted at 09:29h, 26 January Reply

      Hey Sean… I’d see what jets came with it. It could be they are incorrect for your riding location.. When I spoke with Jonathan from Sudco International, he told me the correct jets I would need. It ran much better once installed but did have to adjust the needle position.. ever since it’s ran very well. Good luck!

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