TTR125 FAQ - Engine

I want to boost the power of my TTR125. What combination is the best bang for my buck?

I am looking to boost the power of my daughter's 2004 TTR125LE. So far, I have a Two Brothers exhaust and the carb has been re-jetted. Next step would be a big bore kit. I have done some research and the BBR 150 kit gets some pretty mixed reviews. Some say the increase in power is very little. I see you have a 130 kit, and a couple of different cams. In your opinion, what combo would give me the biggest bang for the buck?

The BBR 150 kit is definitely the best bang for the buck for getting more power out of the TTR125. Our 130cc kit is targeted for racers who are only allowed to go 1mm oversize. Those guys would not be race legal with the 150 kit.

What I would recommend to get the most out of the 150 kit would be to add the 26mm carburetor. The stock carb is actually about the right size for a 50cc motor. The stock carb definitely limits the amount of power the motor can make. With the 150 kit, the carb and a good exhaust you should easily double the original bike horsepower. Another thing that will make a big improvement is to lighten the flywheel. We offer a flywheel lightening service.

What is the best way to break-in my BBR 150cc Big Bore Kit?

Should I follow the stock, recommended break in for a new top-end or is there a better way?

Yes there is a better way! Go to MotoTuneUSA.com and follow his break-in method. I started doing this a few years ago and have never had a problem. It just makes sense. The factory does us all a disservice recommending a slow break-in. I think the real reason for this comes from their legal department. They want you to ride your new bike cautiously until you get familiar with it. The break-in period is for the new owners brain - not the mechanical parts in the motor.

I was recently watching a documentary showing sport bikes coming off of a Kawasaki assembly line. Every bike was gently warmed up then went right onto a dyno and did a 'full throttle through the gears' dyno run. Then went off to have the oil drained and get crated up. They wouldn't be doing that if there was some harm to be done to the engine without a slow break-in.

Will BBR Rev Box make my TTR125 faster?

Hi, I have some questions about the BBR Rev Box for Yamaha TTR125. I do not understand where it goes in the line? Is it the coil, the part that provides electricity to the spark plug, or is it somewhere else? Will I get a bit higher top speed? How much more horsepower will I get with it?

The BBR Rev Box replaces the original ignition module. The rev box (ignition module) sends the spark signal to the coil. Yes, you will get a slightly higher top speed and better engine response. The box by itself will not make more power. If you do other modifications then the box will allow getting the most benefit from those modifications.

How do I remove TTR125 flywheel to have it lightened?

My son wants the flywheel lightened on his 2008 TTR12 LE. The manual is not very specific about pulling it off other than saying that you need a flywheel puller and a sheave holder. (Hopefully I can borrow or rent this stuff since I may never need it again.) Do you have any tips, or is the process fairly simple?

When the flywheel is being removed for the first time it can take a lot of effort. Often, it wont pop loose until you are thinking you are about to break something. I tell you this because it helps to know ahead of time that it may be stuck on very tight. You can remove the TTR125 flywheel with a standard automotive steering wheel puller. I imagine you could rent one but it might not be any more expensive to buy one from a discount auto parts store. I believe I've seen them for $15-$30.

The stock TTR125 flywheel is extremely heavy and was designed to make the TTR easy to ride for beginners. If you're looking for better overall responsiveness, having the flywheel lightened is your best "bang for your buck" performance improvement for the TTR.

TTR125 takes too long to warm up!

I just bought my 11 year old son a 2007 TTR 125 for trail riding out here in the desert in SoCal and it takes like 15 minutes to warm up! What should I do about the carb on this bike? Also, what do I give up if I have the flywheel lightened on this machine? Is he going to lose torque?

Yes, the TTR125 is really lean. Click here to see the jet kit we offer for the TTR.

Lightening the flywheel is the single best bang for the buck improvement for the TTR. The only thing you give up is the lazy "beginning rider friendly" throttle response. If you son is a brand new rider I would hold off on doing the flywheel until he has more experience. If he's already an experienced rider he will love the way the bike works with a lighter flywheel.

How much is too much to remove from the TTR125 flywheel?

I have a 2000 TTR125. I would like the flywheel lightened, but possibly not to the extreme. I am looking for something in the middle for a mostly stock setup non-racer. (I may possibly add your ProCycle Power-Up 125cc Kit, with Camshaft in the future). Is this possible? And is there any reason not to do this?

There is no reason not to lighten the TTR flywheel the full amount. Even after lightening the flywheel, it will still be significantly heavier than the flywheel from any modern 450. Lightening is a big improvement – especially on a stock motor. A built up motor will have more power to spin the heavy flywheel but a stock motor gives up a lot of power trying to accelerate the extra mass of the stock flywheel. So it actually makes more of an improvement on a motor that is all stock.

A very light flywheel can make a motor easy to stall and hard to start. It is not possible to lighten the TTR125 flywheel anywhere near that much. We will do the job any way you want but I think you would be disappointed in the results by only removing part of the available weight.

TTR good for mini-motard?

I am a neophtye mini-motard enthusiast that cannot afford to buy ANOTHER bike, however I keep eyeing up my wife’s 2005 TTR125LE and thinking "Hey can I hop this one up?" Can you please offer some advice / experience on whether or not this is a good bike to set up for racing, and offer some cost effective "first" steps to making it a hybrid dirt / track bike?

A – A:

Yes, racing my TTR125 is the most fun I've ever had on a motorcycle. There are lots of mods that will make the TTR faster and better. Here's a list. I will try to put it in a 'cost effective' order:

Rejet carburetor / open up airbox
Stiffer front fork spring
Lightened flywheel
BBR exhaust system
150cc big bore kit (check your race rules to make sure this won't bump you up to a class full of 85cc 2-strokes)
26 mm carburetor
Works Performance shock
17" wheels with Maxxis dirt track tires

Also highly recommended is a BBR frame cradle and chain guide. Especially if there is going to be any jumping involved.