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Project 2

Motoman287's TTR125

The project is by motoman287 from Thumpertalk (with permission)

So, after enough prodding and peer pressure from friends, I picked up a clean '09 TTR125e, and a few weeks ago, a roached out 2004 YZ85. I've done my research, swapped out the forks, have the rear end mocked up, and will hopefully have it welded up by the end of the weekend. Before I get in depth posting pictures and what-not, I have a major question that I haven't seen anyone post much about. Stock rake on a YZ is 26 degrees, while a TTR is 28. The YZ forks are 4" longer, and although the YZ rear raises/levels things, the wheelbase is still longer. Visually, the bike has a choppered look to it, meaning the front wheel just seems to be out front a ways. The ground is frozen here in WIsconsin, so ripping around on the lawn for an accurate seat-of-the-pants test probably won't yield much, as the front tire is shot and the ground hard/slippery. My concern is that it won't steer/handle as well as a stock TTR, or YZ. I haven't seen anyone discuss cutting the headset and changing the rake angle to get it to understeer a bit better. 


Does anyone have any info or input on this subject? For those who have done the swap, how do you feel the bike handles? Does it steer tight enough, or have a vague feeling out front? I could also probably look into different triple clamps to change offset, and slide the forks up in the clamps to get the front end a little closer.


Thanks in advance for any input. I'll be more thorough and detailed with pics later on (rushed for time at the moment). This isn't going to be a mere suspension swap, but a full build. Motor, chassis, everything.

I think opinions vary on which route to take, and I've struggled with which way to go. The fork swap to the TTR is painless, and geometry figuring aside, the rear end swap isn't too bad, just a bit of welding and spacers. Putting the TTR motor into the YZ chassis requires cutting and recreating the frame cradle, and I would guess some custom intake work to work with the yz air box, possibly custom work on the exhaust as well. Probably a horse apiece on the pain-in-the-ass scale.

The end goal is a fun play bike. As long as it handles decent I'll be happy. I Guess my TTR being next to new and the YZ being ratty as all hell was what swayed me towards utilizing mostly TTR pieces. Hopefully a few more people weigh in with some opinions.

Well, finally got a few pictures. Here's the TTR (I almost feel guilty tearing it apart, as it's almost spotless). I already had the tall seat (GYTR) installed.

I rode this thing when I picked it up, everything seemed fine. When I unloaded it at home a few hours later, I took it for a spin around the block, letting it warm up for a few minutes beforehand. My buddy gets on, goes 60 ft, and in the process of clicking 3rd gear, the whole bike just locks up and skids to a halt on him. Top end is fine, I've gotten it started again, but something in the tranny let loose. Can't find neutral, and it intermittently locks the rear wheel up, even with the clutch pulled in. Looks like more work ahead, as it's probably not worth much as it is...

Last weekend I began tearing things apart. Found this once the plastic was removed from the YZ. Couldn't have welded it, huh?:

I got a bit further than this picture shows. The YZ swingarm is on the TTR frame for mock-up. I need to make a few spacers and the new linkage mount tabs. Probably won't get back to this until after the holidays. I did feel compelled to spend money on something, so ordered up a set of Dunlop MX32's today, which will just sit on the shelf for a while, but it made me feel warm and fuzzy for a moment.

So, no real updates at the moment (been out of town for most of the last few weeks for work, and the holidays aren't helping). The tires came in, which felt like an early Christmas present to myself.


I'm going to run the shock reservoir on the left side of the bike so that I can run the stock airbox/intake setup vs. running a pod filter on the carb (personal preference), but that means I'll likely have to cut and re-weld whatever exhaust I go with to dip below and clear the reservoir. Having to cut and re-weld, my thoughts are I'm best off going with a pipe that has a "raw" finish to the header as opposed to something shiny or ceramic coated, like a Big Gun. From what I'm seeing, my options are the FMF 4.1, Pro Circuit, and DR. D pipes, unless I'm missing something. Does anyone have any input or preferences in regards to these pipes? Initial research is looking like most people think the FMF is over-rated. My plans for the motor are to build something with a bit more power than stock, but keep it reliable. Nobody needs to remind me that I'm polishing a turd here...I have a 250f if I want to ride something with actual power. Pure pleasure is all I'm after with this one. Initial thoughts are BBR filter kit, lightened flywheel, cam, porting, bigger carb, and exhaust. I'm not sold on the BBR 150cc kit just due to the thinner cylinder walls. Would the mods mentioned be worthwhile coupled with a high compression Wiseco? What I'm after as far as motor characteristics is something that revs decent without giving up too much low-end, if that's possible.

I'm hoping to get back on this after the holidays. Once I nail down what I'm after I can start ordering goodies.

Alright, so I'm reviving what probably seemed like a dead thread. I'm a little late for riding season, but am finally almost ready to start slapping this thing together. I've amassed a pretty big collection of parts over the winter, and am waiting on a few spacers to do the frame modifications for the rear end. After that, it's strip it down, off to powdercoat, during which I'll tear down the motor and work some magic there. 


My motor setup is going to be the BBR hi-flow filter, Web cam, ported head, Barnett clutch kit, remove the counterbalancer, lighten the flywheel, ProCom rev box, 13:1 high compression Wiseco (stock bore), and Pro Circuit Exhaust. Everything is purchased, so there's no going back now. My big question with this setup is carb size. Is a 24mm ideal, or a 26? I'm leaning towards the Mikuni VM roundslides...

Well, I ordered and received the VM24 carb. Should have the frame done this weekend. Once I tear it down to send out to powdercoat, I'll dig into the motor. Probably pull the counterbalancer, and put the flywheel on a diet, too.


Aside from chain/sprockets, some graphics, maybe some handguards, and some talon/excel wheels, I think I have everything...

Well, progress was made over the weekend...I basically copied SettinTrendz' build on Planetminis, using top-hat shaped spacers welded in for the top shock mount and swingarm mount to eliminate fumbling with spacers when assembling/disassembling.


I cut 3 different tabs for the linkage relocation, varying 15 degrees each. Ended up going with the most severe angled ones.

Here are the various spacers needed.

Rear brake reservoir tab. I'm planning to keep the electric start, so tucking this behind the RH number plate seemed like the best option. I'll have to trim a tab on the backside of the numberplate to fit around this, but that doesn't concern me. If a person wouldn't run E-start, the space occupied by the battery would free up, allowing for plenty of space for this.

Master cylinder mount. I probably overbuilt this...could have been 1/8" material, I went 3/16". It looks crooked because the battery box doesn't sit parallel with the frame rail..

Swingarm pivot spacers tacked in.

Upper shock mount spacers tacked.

I didn't get pics of the tabs to relocate the lower linkage. If anyone wants some I can get them. Also, the shock spring will rub on the backbone of the frame, so it was cut and plated in.


Before the motor was pulled to finish welding everything out, the exhaust needed some attention. Any exhaust for the TTR isn't designed with having to clear a shock reservoir in mind, so some cutting/welding was required. The pipe is already stepped twice, so cutting the existing welds doesn't change the appearance. Two additional cuts/welds were required in the back section.

Motor pulled, welding completed.

*Full credit to one of my best friends for the welding. 


More to come in the next few weeks...

Well, as usual, it's been a bit between posts. Just a few updates...frame is back from powdercoat (I went stock-looking, gloss black). I sent my suspension out to Race Tech on Friday, should arrive to them today. Assembled the motor last weekend, but ran into another snag. I am running a 13:1 Wiseco (spec'd for a Yamaha Raptor 125 atv actually), and a Web cam. Slight interference between the piston and exhaust valve, so a bit more relief is going to be needed to be machined into the piston. Hopefully taken care of this week. Ordered wheels (black Excels with anodized blue Talon hubs) and Galfer wave rotors. Received the rotors and rear wheel, still waiting on the front. 

At this point, I'm just waiting on the engine and suspension, and can go to town assembling, as I have pretty much everything I need, aside from graphics (ordering this week), and chain and sprockets. I started to reassemble, threw the triple clamps, bars, wiring, airbox, tank, and a few other things onto the frame.

Here's a question for some of you (Greenducky55?). Any suggestions on gearing? I should (hopefully) have more power obviously, so I was thinking about a tooth bigger on the countershaft sprocket, and if not leaving the rear stock, dropping a tooth or two. It's alot cheaper to buy front sprockets than rear, so I'm hoping to get close on the first try...

Ordered my graphics yesterday from DecalMX. Also ordered rim strips, tubes, rim locks, front and rear sprockets, and rotor hardware. I ended up going 14/49 (ordered before I saw MindBlower's post; thanks for the response!). I don't like the thought of "making" clearance on the case for a 15T, so if I end up dropping a tooth or two in the rear eventually, it is what it is. 


I'll probably run the forks up in the clamps a bit, and am also having RaceTech shorten them internally by 1". Hopefully it all works like I'm hoping...


Just need a chain (ordering today), and if I feel like doing a few more things later on, I can, but they won't affect things right now. Debating handguards, anodized timing plugs, unbreakable levers, stuff like that...

Just a few photographic heart surgery, and put the heavy pig on a bit of a diet while I was in there, removing the counterbalancer.

Just a few photographic heart surgery, and put the heavy pig on a bit of a diet while I was in there, removing the counterbalancer.

My hometown is about 2 hours from me, and the motor was tore down at a buddy's place. We thought there was interference between the piston and valves, but luckily the problem was simpler, although made me feel like an idiot. Even though we were sure to check that the cam chain stayed on the crank, it must have slipped off when assembling the head. As we turned the motor over by hand, the chain was skipping (not on any teeth obviously), so the cam was several degrees off. 

Because my buddy was bored and looking for an excuse to get up in the air, he flew it over to me Sunday night. Makes me feel like a factory rider or something...

I'm still waiting on my suspension, probably sometime next week, so in the meantime have been slowly doing what I can. I got the motor back in the frame where it belongs, put the new Galfer wave rotors on the wheels along with rims strips and rim locks, and started putting on some graphics (You're just getting a sneak peak; I can't show them off until it's together).

Since the above photos, I've mounted the tires on the rims, so they're sitting there ready to go. I threw in the BBR filter, cut the top of the airbox out for more flow, threw the pegs on, throttle assembly, and got the carb hooked up.

My bike being a 2009, it uses the dual cable, push/pull throttle assembly. An '07 and older TTR setup is single cable, so I purchased everything needed for that. Rather than outline everything I had to do to make it all work, I'll just provide the link to another guy's website that I found. He lists all the part numbers and everything needed to put a VM24 carb and throttle assembly on. One thing to note, on his site he mentions the need to buy an E-clip to hold the elbow into the carb cap; I purchased a kit from motosport that provides the elbow and adjustment nut, along with the dust cap and stuff. This kit provided an E-clip, so no need to source one elsewhere. Link below:


I'll have to get my swingarm and linkage bearings in before the suspension gets back, too. I started to remove the swingarm bearings last night. 

Well, I'll hold off on judging Race Tech too much, but at this point, I'd highly recommend getting your suspension done by them in the off-season...they've had my stuff for over a month now, claim it will be done today. 


I'm not sure if I would encounter detonation issues with the higher compression on pump gas, but I threw some race fuel in it, filled it with oil, and crossed my fingers this weekend. It fired up within two seconds and idled perfectly, so that's a bit of relief. With any luck, maybe I'll have a bike together by the weekend depending on suspension...

Few updates:

First, I have yet to test the suspension, but FINALLY got it back. 1 week turn-around time turned into 6. I was told it would ship three different times before it finally did. Each time, I was told I'd receive a tracking number, and didn't. I had a discount code (from, that I requested to be applied, which wasn't (until I called them about it). Not real impressed with the customer service...



Bling factor ($12 off E-bay, from Hong-Kong):

One thing to note for anyone who might do a similar build is that if you run the shock like I did with the reservoir on the LH side to retain the stock air-box, the reservoir will interefere with a nipple on the airbox. The nipple is where the crankcase breather attaches, re-routing back into the airbox. I got a different piece of hose and just ran the breather down the backside of the motor, and cut the nipple. I then sealed it with black silicone. 

I haven't taken pics yet, but I do have the swingarm and wheels on it. Just waiting on a few last minute pieces. The pins that hold the rear brake pads in the caliper were stuck/stripped, and the diaphragm and bushing in the brake reservoir was missing. Once I have the new parts, I just have to bleed the brakes, set the controls where I want them, throw grips on it, and tune everything (jetting and suspension). I'll try to post a few pics this weekend.

I realized I never did bring closure to this thread...

It's long since been finished, have plenty of time on it. The suspension was a bit soft for super aggressive riding, but I still haven't addressed that. Otherwise, it's a blast, and I'm happy with it. It's got a very electric feel to the motor, no hard hit, but pulls good. Being stock bore yet, it will run with a buddy's XR100 with BBR120 kit in it, and also with a different buddy's TTR with BBR 150 kit. It lacks the low-end of the 150 kit, but has more over-rev up top. 

I made several extra kits for doing the rear end conversion, if anyone is interested in doing a similar build at some point.

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