31 May 2016 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!
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…
Mikuni VM24 from Sudco International, Part # MI 001.018
- 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…
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.
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.
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!