PlanetMinis Forums banner
1 - 11 of 11 Posts

1,328 Posts
Discussion Starter · #1 ·
phoneman said:
They aren't all toads.If you'll invest a little.Put 85 forks,high compression piston,decent cam,pipe,regear,aluminium rims and they are alot of fun..

So since a few of us are building TTR125's I figured I'de start a new thread. Mine's a recovered stolen bike I'm rebuilding on the cheap for a friend. Got all the parts necessary; (mostly bearings, paint, & plastic). And ALOT of cleaning. Waiting to get the steel swingarm back from powdercoating now. Found a ProCircuit pipe for $75, since the rusted exhaust that was on it had the worst re-welds i've ever seen, plus I think some mice built a nest in it. All full of crap. Needed a whole new rear wheel for it too. The little ******** that stole it had evidently put a different wheel on it with no spacer on the sprocket side. (No idea what wheel it is, had a cush drive in it?) Rusted spokes, black drum hub, POS.

The good news is I think the D-bags parked it before they did any damage to the engine. So I'm wondering, what are some cheap power gains for this motor? Will a new cam with a stock motor make much difference? Can I do a hi-comp piston with the stock jug & head? So far I've just got the PC pipe and I've done the airbox mod.


1,092 Posts
My buddy has a couple of ttr-125's that he has built up, whatever you do don't get stiffer springs for any of the stock suspension. They are a complete waste of time and make next to no difference. Go with 85 forks up front and maybe a 150 kit and you will be set.

1,328 Posts
Discussion Starter · #5 ·
Yeah, if it was my bike I think I'de make it a motard and mod the hell out of it. But, this one's for a 12 year old who hasn't ridden anything. Should be a good starter bike for him. It's probably going to go back to the farm though, likely anybody could be riding it. I found some GYT-R heavy springs F&R for cheap, so even my fat-ass cousin (not 12 years old), won't blow the fork seals. Found a BBR frame cradle too, so hopefully the bike will be fairly durable. I'de like to get a different carb maybe, since the stocker sucks. I got a replacement stocker carb for cheap since the original one's choke plunger was completely seized up. It'll work for now I guess. I still can't believe the cops finally found it after three years gone missing.

1,328 Posts
Discussion Starter · #6 ·
Mxfreak_24 said:
My buddy has a couple of ttr-125's that he has built up, whatever you do don't get stiffer springs for any of the stock suspension. They are a complete waste of time and make next to no difference. Go with 85 forks up front and maybe a 150 kit and you will be set.

haha..oops..I spoke too soon. Well maybe my fat-ass cousin will blow fork seals afterall. We'll make him stick to driving the

1,328 Posts
Discussion Starter · #7 ·
Thanx for saving this phoneman! I just found it! I'm going to repost here too so I'll know where to find it. Great info!

For any "TTR Old Timers": During the format change (05/16/04) I copied this posting by Donkey and saved it on my PC. During the format change, this ENTIRE posting disappeared. Hence a very slight change in this post: my name appears as the poster vice Donkey who gets ABSOLUTE 100% credit for this!!!!


1. Stock carb jetting

Mikuni VM20SS

17.5 pilot

110-120 main, (depending on mods)

The needle works best in the stock position, or middle clip.

Jets can be found here: SUDCO Motorcycle Parts Distributing The mains are the N100.604 Large Round Type, and pilots are the VM28/486 Type.

You can order the correct TTR125 jets right from the Thumpertalk marketplace.

Large round type Mikuni main jets (N100.604)

107.5 TT part #MK-183

110.0 TT part #MK-184

112.5 TT part #MK-185

115.0 TT part #MK-186

117.5 TT part #MK-187

120.0 TT part #MK-188

VM28/486 Pilot Jets

17.5 TT part #MK-031

20.0 TT part #MK-032

They're $1.93 each

Here's a link to a detail drawing of the pilot and main jets in the carb of a 2002 TT-R125L. Bear in mind this bike is a California model:

TT-R125L Pilot & Main Jets

2. Airbox Mod

Consists of removing the snorkle/plug from the top of the airbox and removing the screen from behind the filter. Every TTR should have this performed immediately upon delivery. Even more air flow can be achieved by cutting out the entire top section of the box and adding a high flow aftermarket air filter. This will require a richer pilot and main jet and tuning of the fuel screw to get the best response and power. However, it should be taken into consideration that the more extensive airbox mods may not be a good idea for someone who rides in extreme conditions often. With the top completely removed water or sand could easily get into the box and cause the bike to run poorly.

3. Flywheel mod

Basically, the flywheel creates rotating mass in your engine, keeping it spinning when you let off the gas. The "flywheel mod" involves machining material (up to 18oz.) from the flywheel, making it lighter, and in effect, allowing your engine to rev faster, or "spin up" quicker. The drawback is that the engine is easier to stall. Some internet companies charge over $100 for this service, but most local machine shops will usually do it for as little as $25. Overall opinion is that this is a very worthwhile mod for the money, but is better left to the more experienced riders.

4. BBR frame cradle compliancy

The BBR frame cradle is an essential item for the TTR. It adds much needed ridgidity to the frame and also protects the engine, while at the same time, being very light weight.

These pipes have been proven to fit well with the BBR frame cradle:

BBR (of course)


Pro Circuit




Engines Only


Big Gun

Pipes that have been proven not to fit:

Stock pipe (oddly enough)


White Brothers

5. Handlebars and Handguards


The stockers are weak, but there are many aftermarket bars to choose from in all shapes and sizes. However, most every rider prefers a slightly different setup, so you need to put some thought into how you like to feel and position yourself on the bike beforehand. The best thing to do is measure the stockers up, and compare those #'s to what's listed on the Renthal/TAG/ProTaper web sites. That way you can get a good idea of what you want, and what to expect. Oversized, 1-1/8" bars are great, but will require adapters or a new triple clamp. They damp out most of the vibration and resist bending like you wouldn't believe. Not to mention the fact that they look cool. But the extra thick 7/8" bars aren't bad either, and will bolt right up with no extra parts to purchase. You can buy your handlebars from a million different places, but look around for the best deals. TAG, Pro Taper, and Renthal all make oversized billet adapters for around $75, but remember, they raise the bar height 3/4 of an inch themselves, so keep that in mind when figuring out which bend you want. Triple clamps with oversized mounts can be found here: RSWRacing and here: BBR Motorsports, Inc At prices from $100-200. I suggest the RSW triple clamp. Ron also makes a very nice and highly effective billet fork brace, which at $70, is probably the best deal on a performance accessory that you'll find anywhere.


The Acerbis Rally Pro's are the best thing goin' at $75. But reguardless of brand, the key is the sturdy reinforcing aluminum backbone. The plastic brushguards do little to protect your hands or the levers during a get off. If you are using oversized bars, you'll also need adapters for the handguards. Of course, all the major players can supply you with their version, and all seem to work well. With good bars and handguards your bike becomes almost indestructable. No more bent or broken levers. And no more fingers smashed between the bar and the ground.

6. Other Basic Mods

Sprocket changes are sometimes necessary. For more top speed go with a larger front sprocket or smaller rear. For more low end power do the opposite, smaller front or larger rear. The 14 and 15 tooth front sprockets work well and are readily available from Sprocket Specialists here:

Sprocket Specialists

They also have a wide selection of much lighter aluminum rear sprockets.

An actual chain guide is another well advised security mearsure for the TTR. There are many on the market, more popular versions being sold by BBR and PRC.

A stainless steel brake line is one of the best $$$ value mods available, and adds great feel and extra power to the TTR's front disc. I prefer Goodridge lines and have used them on all my bikes for a long time with great success, but there are several other brands available. Galfer, Speigler, Russell, ect... Most any manufacturer can make a custom line in any length you need with all the hardware in any configuration you want. Prices range from $50-90. Keep in mind, the stock rubber lines are supposed to be replaced every two to three years. Stainless lines are good for at least 10.

Brake pads can also be upgraded. The stock pads offer decent feel and power, but they overheat and fade quickly with the small rotor. Again, there are several brands on the market to choose from, and many times it comes down to personal preference.

7. YZ carb mod

The last generation of round slide carbs from the YZ80 make great improvements to the TTR for little $$$ and fit right up with no modification. (2.5mm can be milled off the engine side for a perfect fit, but is not necessary.) They are particular about jetting, but make very good power. Look on Ebay and in junk yards for a clean model from 1982 to 2001. They are all basically the same and can be had for as little as $20. Strait from a YZ, they will be very rich on top and bottom, and lean in the middle on the TTR. A good place to start with rejetting is a 20-22.5 pilot and 140-150 main. The best needle is still undecided, but any of the richest Mikuni 4 or 5 series needles could work. (The stock YZ needle seems to fall just on the rich side of the middle of the charts in the Mikuni catalouges.) Slide sizes could also be changed. The YZ's slide is a #3. A #2 or even #1.5 could work well? Many folks have opt'ed to replace the stock O-0 needle jet with a P-4 size and keep the YZ needle. This seems to work well too. But remember, jetting will be different on nearly everyone's bike, so what works great for one, may not work as well for another. These are all just generalized places to start. Getting your bike finely tuned is half the fun. But overall, the YZ80 carb mod is very much worthwhile for the added power and response. It also enables the use of a pod filter, which is impossible with the stock carb. All necessary jet's and needles can be found here: SUDCO Motorcycle Parts Distributing and here: Welcome

8. Suspension mods

The best money you'll ever spend on any motorcycle is in getting the suspension dialed in. Not only will it enable you to go much faster, but you'll be doing it with less effort and more direct control of your bike. There are several routes that can be taken to upgrade the TTR's stock suspension. The easiest, and most common thing to do is add heavier aftermarket springs front and rear, thicker oil to the stock forks (10-15wt.), and purchase stronger billet triple clamps and a fork brace.

Those mods alone make terrific improvements over stock, but can still fall short for many larger and/or more aggressive riders. The ultimate suspension upgrade for the TTR125 is to replace the entire front end with an inverted forked, and much more rigid, '94-03 YZ80/85 or KX80/85 front end. You'll need to change the springs to match the heavier bike and there's some simple adaptation required. The YZ forks are much longer than the stock forks and can be shortened to maintain the stock ride height or a BBR swingarm can be purchased to raise the rear 1.5". They will also need to be matched up with a shock in the rear that can equal their performance level. The Works Performance shock seems to be the popular choice, but the newer generation TTR shocks with the remote resi can be rebuilt with a good deal of success.

9. Motard Conversion

The most common modification is to lace wider aftermarket 17 inch rims, such as Excel or Sun, to the stock hubs with heavy duty spokes. They are available here: Buchanan Spoke and Rim, Inc. and here:

All year model TTR's with a stock or YZ/KX front end can run either a 2.5/17" or 2.75/17" front rim. The 2.5" is the prefered and standard 125GP size, but restricts your tire choices to full blown race tires if you want the proper profile to be maintained. The 2.75" rim is wider than necessary, but allows the more common 110/60 size sportbike front tires to be used without distorting their intended profile. Whether you are able to use the entire tire surface with that size has yet to be proven, though.

All '02 and older TTR's, and newer standard and "L" models without the aluminum swingarm, are restricted to a 2.75/17" rear rim with a 110/70 tire. The '03 and newer "LE" models with the wider aluminum swingarm have the choice between the 2.75/17", or the prefered 125GP sized 3.5/17", rear rims. The 3.5" wide rear rim allows you to run tires up to a 120/70 without any issues. 120/70 is the most common size of sportbike front tire, and they work great as rears if turned backwards. High performance street tires, DOT race tires, and full blown slicks are all available.

The 125GP setup (2.5"f, 3.5"r) is more restrictive as to front tire choice, but offers the best performing tires and sizes, and easily available rears in the most common size of all. Only three manufacurers make tires for the 125GP bikes, Michelin, Bridgestone and Dunlop, but they are all very good. A set at retail is expensive though. $200-300 front and rear. You do have the option of slicks or rains, and Dunlop and Michelin offer two compound choices. Much cheaper take-offs are out there to be had too. The Dunlops feel great and last a very long time, but are a harder compound rated for higher temps, so they take a while to "come on".. They also have a very stiff carcass so they tend to chatter more than slide sometimes. The Bridgestones and rated for a much lower optimum operating temp, so they heat up faster and work better at the lower temps that the TTR is likely to see. However, they are softer and don't last nearly as long as the Dunlops. They are cheaper though. The Michelin front tire doesn't suit my riding style, but I do like their rear tire.

The 2.75" setup has it's advantages in the fact that many decent tires are readily available, and can be had for cheap. However, it doesn't offer the all-out performance potential of the GP setup with slicks and a fatter rear. The steering is a little slower, and the response isn't as good with the wider tires. But there's plenty of grip to be had with good street tires. It also takes a lot more suspension to deal with the super grip of the slicks. Street tires may be just as fast, if not faster on some bikes.

10. Extreme Tuning

Of course, there are those that will never be satisfied with the amount of power their bike makes. Thankfully, I'm one of you.

The sickest power mods for the TTR begin with the camshaft. BBR, Powroll, PRC, and HotCam all make excellent cams for the TTR. I love my HotCam and Wiseco makes a drop in 11:1 high compression piston that works great with it.

Next up would be porting, polishing, and head and valve work. In this area it's really all about who you know and how good they are. I doubt you'll pry any secrets from the real competitors about the specifics here. Just have to find out for yourself. But the TTR's do have a good bit of power in there.

Big bore. What else needs to be said? There are several 150 kits on the market, and Powroll even offers the mac-daddy 170 stroker. And if you can't find enough juice for your TTR in 170ville then you've got the wrong idea entirely.


BBR - BBR Motorsports, Inc (BBR Motorsports,)

Powroll -

RSW Racing - RSWRacing

Sprocket Specialists: Sprocket Specialists

Sudco - SUDCO Motorcycle Parts Distributing

79 Posts
Phoneman could be right about the crank and bearings, especially a used TTR that has been hammered. I got my '05 in 06 and just modded out the motor 8 mos. ago. 20hrs on the big bore kit and still running strong. These little bikes are pretty much bullet proof, especially if you take care on them.
1 - 11 of 11 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.