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TTR125/YZ85 Conversion Question

30K views 38 replies 10 participants last post by  pitbikeman 
#1 ·
I'm starting a conversion build, and in all my reading up on things, I haven't seen much talk about the rake angle/handling. I know the stock rake angle on the YZ is 26 degrees, the TTR is 28. Once I threw the everything on my frame, the front forks just seem to stick out a ways up front. The TTR frame is straight, not bent. Does the steering feel vague, or does it handle decent after the conversion? I want it to understeer and turn decent.

Thanks in advance!
 
#2 · (Edited)
Do you have a big wheel model or small?

Some guys slide the forks up in the clamps but with the big wheel the tires hit the fender on big jumps really easy if you do this. Small wheels have more room.

A few guys have had custom clamps made to reduce the rake.

Rasing up the rear of the bike helps. Either a longer clevis, longer shock. Or drill the mounting hole to raise the ride height.

But overall the bike does have slower steering than stock. I'm used to it and don't mind.

This is how mine sits on a stand. I redrilled the shock hole 1" down and 1" back. It leveled it. I had a softer ride than before. I recently resprung and revalved but have yet to test it.

Land vehicle Vehicle Motorcycle Enduro Motor vehicle


This is the best pic I have of it on the ground.

Nature Vehicle Tree Motorcycle Wheel
 
#37 ·
Do you have a big wheel model or small?

Some guys slide the forks up in the clamps but with the big wheel the tires hit the fender on big jumps really easy if you do this. Small wheels have more room.

A few guys have had custom clamps made to reduce the rake.

Rasing up the rear of the bike helps. Either a longer clevis, longer shock. Or drill the mounting hole to raise the ride height.

But overall the bike does have slower steering than stock. I'm used to it and don't mind.

This is how mine sits on a stand. I redrilled the shock hole 1" down and 1" back. It leveled it. I had a softer ride than before. I recently resprung and revalved but have yet to test it.

View attachment 169251

This is the best pic I have of it on the ground.

View attachment 169252
As for trying to get better handling, the Ride Engineering clamps have 2 spots for the bottom clamps to bolt up and the front option can give more handling without having to raise the forks in the clamps. Also, gets the bars out of your lap, too.
 
#3 ·
I do have the small wheel version and am adding the yz rear end as well to raise it. Any suggestions on where to source clamps? I've also considered modifying the head of the frame to bring things in a bit but would rather avoid that if I can.
 
#4 ·
i know Topat racing can do custom clamps, I don't know if they will do rake or offset modifications but doesn't hurt to ask.
Emig racing also does custom clamps but the price is high. and i believe RSW racing can hook you up as well.

this are just places that i know who do custom clamps. There are a few forum members here s well who make clamps, i've mainly seen it in the ATC builds where people use zokes on them.
 
#5 ·
I don't feel the rake was too bad on my build. I have the 85 rear end and shock in my shop but it ended up being too much work for me to get it to bolt on with the correct progressive shock angle so I just bought a new gold chain and threw a ttr225 shock on mine. It's bolts right on with the longer chain. And I think she sits pretty even. It's a bike I built for the girl friend she seems to like it alot. I also threw on a yz85 28mm carb and I can't believe how much more power it produced. But here is mine Land vehicle Vehicle Motorcycle Supermoto Motorsport
 
#7 ·
I didn't measure but off a guess 2-2 1/2 inches. Matched with the front fork conversion nicely I think
 
#8 ·
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.

Thanks again for any replies. I'm hoping to get back on this after the holidays. Once I nail down what I'm after I can start ordering goodies.
 
#9 ·
Still undecided on which way to go with the motor...seems opinions are mixed on the BBR 150 kit being worth it, and also on which cam is best. I've been collecting parts, hoping to start throwing things together soon. So far I have a Pro Circuit T-4 exhaust, BBR filter kit, Dunlop MX32's, new bearings for the shock, swingarm, and linkage, GYTR tall seat, BBR engine cradle, Motion Pro fork bleeders, a Barnett Dirt Digger clutch kit, and a TM Designworks chain guide/slide kit.

I still need to order bars, pegs, shifter, chain/sprockets, and figure out my motor. Open to any new suggestions...

(I know, this thread is worthless without pics).
 
#10 ·
Here are some options for you and my opinions.

Stock bore or bore stock sleeve max of 130cc with either a pmw 13:1 or weisco high comp piston. An aftermarket cam (hot cams, web cam, BBR, PMW) lighten the flywheel up if your in the cases remove the counter balencer. If you have confidence in your e start (or have it) remove all the kick start gear for some weight redux. Bbr filter kit and a carb upgrade. Rev box has mixed opinions I had one was nice to rev a little farther on longer straights. (This was my previous setup minus the flywheel and I had tons of fun on it but that's me)

BBR kit tried and true works well with exhaust flywheel, counterbalance removal, carb*** rev box (your choice) I've ridden one it had more go than mine for sure. You basically have to do the supporting mods to really use it. Our stock carb is crap.

This new 170cc bore on eBay. I have no clue but the piston is cast and lookks low compression. But I know a place that can fix that and not cost an arm and a leg. Should be an upgrade for sure but you'll need (cam, carb, filter, exhaust and probably port work to make it scream)

4 valve head: gncc proven by PMW and FPM on the raptor 125. PMWwill not sell you a kit requires your motor to do the conversion. Or a core swap, custom order anything you want basically. Claims good increase in HP and TQ. Downsides, turn around time, price $$$ most expensive option.

4 valve head diy(kinda) be ambitious like me and buy a craps ton of parts and hope they work and learn your mistakes.
Pros: can do whatever you want. Possibly cheaper if you get it right the first time.
Cons: need a good machine shop willing to deal with all the work involved if you can't do it yourself. Delays, availability of a few major parts. (Cam sprocket** motor cant run without one. Your cylinder head has to have the correct oil port) and the list goes on.

Hopefully those are helpful it all comes down to what do you want to spend. Best bang for your buck is option 1 and 2.
 
#11 ·
I saw the 170 kit on Ebay, and think I'll pass. I'm not out to create a monster, just good, usable power over stock. Looks like option one or two. I was told by Pro Cycle that a decent carb is no longer available for these? I want to retain the stock airbox and boot setup.

Thanks for the input.
 
#12 ·
The carb is still available just not the expensive version from bbr.

You can pick up a mikuni vm series carb fairly cheap. If stock bore is you plan I'd say a vm 24. If you going with big bore I'd say the vm26. Make sure you get a genuine mikuni don't get the knock off its not worth the headache. You cCan get one from a atc200, crf230 and a few other bikes used. Or go brand new you will just have to play with jetting. Also I believe bbr still sell the carb adapter. You'll need the throttle set up from the carb as well.

I agree on the eBay kit not worth the risk lol.
 
#14 ·
Check with Race Tech. That's who I plan on going with...I believe there's another build thread on here (Fatman*** something or other is his username) where he had them shorten his forks internally.
 
#18 · (Edited)
The total was $510 and a week turn around time. I have not ridden it yet. The springs are 36s. I don't know...I think they should have been more but I'm only trail riding so maybe it'll be okay. They also shortened the ride height an inch. I pushed the fork tubes down in the clamps to help keep the tire away from the header pipe.

Land vehicle Vehicle Motorcycle Car Enduro

Land vehicle Vehicle Motorcycle Enduro Supermoto


My bbr spring came in right after I got everything back together. Oh well.
 
#19 ·
Well, frame should be welded up this weekend, then off to powdercoat. Almost time to finally make something happen here...

Toy Auto part Fictional character Automotive tire Transformers


Auto part


Auto part Bumper Tire Automotive tire Automotive exterior


Tire Personal protective equipment Footwear Auto part Shoe


Tire Automotive tire Toy Wheel Automotive wheel system
 
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#20 ·
Well, progress was made over the weekend...I basically copied SettinTrendz' build, 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 (top ones in the pic).
Blade


Here are the various spacers needed.
Auto part Hardware accessory


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.
Tire Automotive tire Auto part Vehicle Brake



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...
Auto part Fuel line Vehicle Engine Tire



Swingarm pivot spacers tacked in.
Auto part Engine


Upper shock mount spacers tacked.
Auto part Fuel line



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.
Land vehicle Vehicle Motorcycle Engine Car


Motor pulled, welding completed.
Land vehicle Vehicle Motorcycle Car Enduro



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

More to come in the next few weeks...
 
#22 ·
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...

I'll try to get some pictures soon.
 
#23 ·
Ended up going with 14/49 gearing (stock is 13/49). If I need to make changes from there, I'll probably drop teeth in the rear.

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

Engine Auto part Automotive engine part Carburetor Technology
Machine tool Auto part Gear Machine Transmission part


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...
Vehicle Driving Vacation Glasses Boating


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).

Bicycle wheel Spoke Tire Rim Bicycle tire
Tire Automotive tire Cobalt blue Rim Auto part
Engine Auto part Automotive engine part Vehicle Car


Hopefully I'll have time tonight to do a few more things. Throw in the BBR filter kit, throttle assembly and carb, footpegs, and shifter. I'll have to get my swingarm and linkage bearings in before the suspension gets back, too. More updates to come in the next week.
 
#33 · (Edited by Moderator)
Ended up going with 14/49 gearing (stock is 13/49). If I need to make changes from there, I'll probably drop teeth in the rear.

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

View attachment 177481 View attachment 177489 View attachment 177497

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...
View attachment 177505

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).

View attachment 177513 View attachment 177521 View attachment 177529 View attachment 177537 View attachment 177545

Hopefully I'll have time tonight to do a few more things. Throw in the BBR filter kit, throttle assembly and carb, footpegs, and shifter. I'll have to get my swingarm and linkage bearings in before the suspension gets back, too. More updates to come in the next week.
I have a question about removing the counterbalance. Does doing that add more torque and throttle response and not hinder any performance along with lightening up the flywheel? I want to start building my ttr125 up to a ridiculous level like big bore, cam, maybe a CRF230F carb with the bbr plate adapter to accept the xr200 intake manifold (to keep the dual cable setup on my 2013), lighter flywheel, custom exhaust, maybe a ktm 85 hydro clutch for s**ts and giggles, big wheel set up and everything, plus removing the kickstarter and running an oil cooler, and porting and polishing the stock cylinder head for now. Any advice in doing the procedure of its beneficial?
 
#25 ·
So the raptor 125 piston worked? Lookin for easy mods for a little ttr I picked up
I haven't fired it up yet, but I'm assuming it will work. It turns over with no interference, and like I mentioned in a previous post (I think?), I found out by reading about a guy using it on a different forum.
 
#26 ·
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...
 
#27 ·
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 Pulpmx.com), that I requested to be applied, which wasn't (until I called them about it). Not real impressed with the customer service...

Pre-suspension:
Tire Automotive tire Vehicle Auto part Spoke


Vehicle Automotive tire Motor vehicle Tire Automotive exterior


Post-suspension:
Auto part Vehicle Engine Automotive exhaust Suspension


Tire Vehicle Bicycle wheel Automotive tire Auto part


Bling factor ($12 off E-bay, from Hong-Kong):
Engine Auto part Vehicle Automotive engine part Car


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.
 
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#28 ·
Well, it's done. I threw the stock YZ wheels on it just for running up and down the street to dial my jetting a bit, and then took it to my neighbor's mini track to see how things felt. Initial impressions are that after setting my sag, the Race Tech stuff works very well. Plush, but never bottoms, soaks up chatter great. Crappy customer service (in my case, at least) aside, I'm pleased. As for the motor, it pulls decent. I didn't know what to expect, but running up a big hill side by side with an XR100 sporting a BBR 120cc kit, 26 mm carb, and exhaust, it seems to pull on it slightly. I'm probably lugging around a bunch of extra weight over that bike though, with my e-start and battery.

At the end of the night, a buddy and I switched bikes for a few laps. We didn't make it two laps even before he ended up going down on a step-on, step-off. Bars folded down to the tank, bent the key/ignition, and bent the f. brake lever, along with giving himself a concussion. I guess it's broken in now. Will be washing it up, throwing the new wheels on, and I'll snap a few pics to post here.
 
#30 ·
Here it is, that's it, that's all. Just missing the brake lever...I will try to get a video of it in the next week or so. I think I can clean up my jetting on the low end, just a bit, as it has a slight stumble off idle. I'm also going to experiment with gearing. I went one tooth larger on the front over stock, but may go back down. Right now second is decent, but third could be a bit more usable. Some corners I find myself wanting to stay in third, but it just doesn't have quite enough to pull it like I want.


 
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