DT125R ARCHIVE

NEV · Guru

RE: Yamaha Dtr 125cc SM 2002

miguelNS · DTR Respected Member

Ahh!! But those are really clouds :p

miguelNS · DTR Respected Member

I can assure you that's no tzr exhaust, itss handmade for dtr stock engine :)

NEV · Guru

regardless whether it is a tzr or not, the longer stinger gives it an edge.

miguelNS · DTR Respected Member

edge of what?

NEV · Guru

advantage

miguelNS · DTR Respected Member

its not the stinguer thats going to make much difference. the exhaust is designed and built in a way to take all the power that the stock engine produces, and believe me, its a lot. many people think that dtr engines are ****ty engines, but there are many bikes that reach over 150 km/h with stock engines :)

DT-R_bradders · Guru

not the best diagrame but it give u an idea http://dt125r.activeboard.com/t41670331/understanding-how-a-2-stroke-engine-works/

the slimmer "stinger" or expansion chamber compared to a shorter fatter one will change the characteristics of the gas pressure rebound in the pipe changing how fast it get drawn back into the cylinder, i dont fully understand what shapes n sizes do what in performance characteristis but i know that it does change it, think it moves the power band higer and lower in the rev rang some giving more top end madness or lower end torque

NEV · Guru

Ya reckon?
I quote from a TZR owner and mechanic who knows his stuff

"if you have the 3mb bottom and top end, then well done, you're onto a winner, i'd recommend just doing exactly what yamaha intended. go for the tzr125rr set up: 32mm dellorto, change the reeds and inlet manifold, and stick a 4dl exhaust on it, but be carefull which you go for, the series 1 and 3 are different, one looks fat, and one has a long stinger, one produces max power at around 10,000 rpm, the other at 11,500rpm, guess which one is more useable!

DT-R_bradders · Guru

ah so he recomends 3mb barrel aswell??? wat bout the 4dl i jus got with better lookin porting more mx stle porting.. lol : /

miguelNS · DTR Respected Member

DT-R_bradders wrote:
not the best diagrame but it give u an idea http://dt125r.activeboard.com/t41670331/understanding-how-a-2-stroke-engine-works/
the slimmer "stinger" or expansion chamber compared to a shorter fatter one will change the characteristics of the gas pressure rebound in the pipe changing how fast it get drawn back into the cylinder, i dont fully understand what shapes n sizes do what in performance characteristis but i know that it does change it, think it moves the power band higer and lower in the rev rang some giving more top end madness or lower end torque

Yes but all that happens in theory.. The only thing that really is veryfied is how fast the gases get back into the cyliinder. And in my opinnion the shapes doesnt make much difference aswell. Because gases go along the exhaust walls, not in the middle, so for many bends the exhaust might have it doesnt make MUCH a difference

miguelNS · DTR Respected Member

NEV wrote:
Ya reckon?
I quote from a TZR owner and mechanic who knows his stuff

"if you have the 3mb bottom and top end, then well done, you're onto a winner, i'd recommend just doing exactly what yamaha intended. go for the tzr125rr set up: 32mm dellorto, change the reeds and inlet manifold, and stick a 4dl exhaust on it, but be carefull which you go for, the series 1 and 3 are different, one looks fat, and one has a long stinger, one produces max power at around 10,000 rpm, the other at 11,500rpm, guess which one is more useable!

But i dont have a tzr engine and having an exhaust that isnt made for your cylinder measures is having something that wont work right

NEV · Guru

Theory?
I'll bet diamonds its been tested, that's why the bloke comes out with the rev range difference

NEV · Guru

miguelNS wrote:
But i dont have a tzr engine and having an exhaust that isnt made for your cylinder measures is having something that wont work right

You'd be surprised how similar a tzr and a dtr engines are, difference is mainly gearing, and 3 gears are the same if I remember correctly

NEV · Guru

DT-R_bradders wrote:
ah so he recomends 3mb barrel aswell??? wat bout the 4dl i jus got with better lookin porting more mx stle porting.. lol : /

I'll cut n paste the whole peice Bradders, you can have a butchers yersen,

firstly to clarify, the 4fu barrel, is not from the tzr-RR, it's from the uk/european spec from the 4hw/4fl
model which is a tzr-R

it's ported slightly different to the 4dl tzr's and dt's, and it's a nicosil plated barrel, with flat top piston, it has slightly different compression to the others, and doesnt produce more peak bhp than the others, actually less, not by a lot, but enough for you to notice, HOWEVER it is ported for functionality, rather than aggressiveness, so it is more useable power, but when on it's standard bottom end, it is less powerfull than the tzr-RR
(please note, if you seize the 4fu barrel it's £100 to £150 for a decent replate, it cannot be rebored!)

next the 3mb barrel and head, nice peice of kit, capable of 33bhp, at the rear wheel, WITH WORK used on the DT-R and the TZR125-RR series 1 and 3 4dl, the italian import model, higher compression, better power, better performance, but higher in the rev range due to the more aggressive porting, the engine casings/crank areas were developed by moto minarelli, for the extra power, and belgarda did all the frame and cosmetic and changing brakes etc.

then you have the holy grail, i'll pay a lot of money to anyone who gets one of these, the actual 4DL sp barrel, it has 4DL stamped on the side of it, and some italian name. and is a massive step up from what we're used to, you cant re-port a 3mb barrel to this level, no matter who you take it to! it is very aggressicely ported, but it's as smooth as a baby's bum from 1000 to 13500 rpm! the engine that had this barrel on it will produce an accliamed 35 bhp, at the wheel. (remember it's acclaimed!)

right, my opinion, do you want a brilliant reading on a dyno, or a good fistfull of useable power, think about this, as tuning options depend on it, i mean why go get it re-ported to produce more power, it your peak power is over the redline, you'd not be able to use it without risking blowing it up!?

if you have the 3mb bottom and top end, then well done, you're onto a winner, i'd recommend just doing exactly what yamaha intended. go for the tzr125rr set up: 32mm dellorto, change the reeds and inlet manifold, and stick a 4dl exhaust on it, but be carefull which you go for, the series 1 and 3 are different, one looks fat, and one has a long stinger, one produces max power at around 10,000 rpm, the other at 11,500rpm, guess which one is more useable!

if you have the uk spec bottom end, be carefull,they look the same/similar as the 3mb, but the flwheel is different, as are the casings, and crank, and an interesting fact, the uk spec (4hw/4fl) tzr125r uses the 2rk con rod from the 1987-1992 model, (not made to handle masses of power) i've had no end of engines come through where people have tried to stick this and that on it, it's gone splat and i've bought it to recondition it. i'd go as yamaha intended, grab the 28mm mikuni carb off a 4hw tzr, and the inlet and reeds to match (if that isnt what yours is running at the moment) IN MY OPINION, DO NOT RUN A HIGH COMPRESSION KIT ON THIS BOTTOM END, IT WILL NOT HANDLE THE POWER, AND IT WILL SH*T ITSELF UNDER STRESS, IT JUST CANT HANDLE IT.

the ram air filters may sound great (that great sucking noise!), but can damage reliability due to the lack of controll of airflow, ideally you'd need to rejet from summer to winter and visa versa due to changes in air density and temperature through the seasons, NOT FORGETTING THEY GET SODDEN WHEN IT RAINS IF ITS NOT PROTECTED! (which isnt the case as much with a standard airbox) but it's a long debate that'll never end, airbox or not airbox or not..... each person prefers their own, but the gp's all use airboxes....... lol

for both engines, tzr125r, and tzr125rr, the best thing you can spend your money on is the exhaust system, and carb, maximum power gains, in the rev range you want it, with only the time consuming task of re-jetting to suit.
that or send the barrel to a well recommended 2t engineer, and tell him what you want from it!

dont know if this helps, but i fancied a ramble on about something, and seeing as the sachs uses the yamaha engine, i thought this seemed a good place to do it!
let me know if i'm wrong on anything, i'm still learning, but after stripping a lot of tzr engines this year, i'm getting there!

last but not least, a little note on bhp, this whole 33bhp marker that everyone chases, it's a very challenging target to find, seeing as even a rs 125, only produces 27-29 at the wheel, the 33bhp claim is the reading taken from the crank! power is lost throught the transmision and the drive gears/chain, and then the tyres, i've seen three brand new bikes from aprillia, straight onto a dyno out of the box, they ranged from 26-28.2 bhp at the rear wheel. and that was back in the day when they were the fastest thing a crazy teenager could buy!

the very very best and top flight of the superteen 125 bikes are only running at 35 bhp, and the top flight only make one race before needing a full rebuild, if they went past arond 35 bhp, the bikes wouldn't even finish the race before falling apart through the strain.

anyone who claims 33bhp at the wheel, show me/everyone the dyno readout, if you got the 33bhp, you've worked hard, tuned very well, spent a lot of money, and got a very fast bike, be proud

miguelNS · DTR Respected Member

NEV wrote:
DT-R_bradders wrote:
ah so he recomends 3mb barrel aswell??? wat bout the 4dl i jus got with better lookin porting more mx stle porting.. lol : /
I'll cut n paste the whole peice Bradders, you can have a butchers yersen,
firstly to clarify, the 4fu barrel, is not from the tzr-RR, it's from the uk/european spec from the 4hw/4fl
model which is a tzr-R
it's ported slightly different to the 4dl tzr's and dt's, and it's a nicosil plated barrel, with flat top piston, it has slightly different compression to the others, and doesnt produce more peak bhp than the others, actually less, not by a lot, but enough for you to notice, HOWEVER it is ported for functionality, rather than aggressiveness, so it is more useable power, but when on it's standard bottom end, it is less powerfull than the tzr-RR
(please note, if you seize the 4fu barrel it's £100 to £150 for a decent replate, it cannot be rebored!)
next the 3mb barrel and head, nice peice of kit, capable of 33bhp, at the rear wheel, WITH WORK used on the DT-R and the TZR125-RR series 1 and 3 4dl, the italian import model, higher compression, better power, better performance, but higher in the rev range due to the more aggressive porting, the engine casings/crank areas were developed by moto minarelli, for the extra power, and belgarda did all the frame and cosmetic and changing brakes etc.
then you have the holy grail, i'll pay a lot of money to anyone who gets one of these, the actual 4DL sp barrel, it has 4DL stamped on the side of it, and some italian name. and is a massive step up from what we're used to, you cant re-port a 3mb barrel to this level, no matter who you take it to! it is very aggressicely ported, but it's as smooth as a baby's bum from 1000 to 13500 rpm! the engine that had this barrel on it will produce an accliamed 35 bhp, at the wheel. (remember it's acclaimed!)
right, my opinion, do you want a brilliant reading on a dyno, or a good fistfull of useable power, think about this, as tuning options depend on it, i mean why go get it re-ported to produce more power, it your peak power is over the redline, you'd not be able to use it without risking blowing it up!?
if you have the 3mb bottom and top end, then well done, you're onto a winner, i'd recommend just doing exactly what yamaha intended. go for the tzr125rr set up: 32mm dellorto, change the reeds and inlet manifold, and stick a 4dl exhaust on it, but be carefull which you go for, the series 1 and 3 are different, one looks fat, and one has a long stinger, one produces max power at around 10,000 rpm, the other at 11,500rpm, guess which one is more useable!
if you have the uk spec bottom end, be carefull,they look the same/similar as the 3mb, but the flwheel is different, as are the casings, and crank, and an interesting fact, the uk spec (4hw/4fl) tzr125r uses the 2rk con rod from the 1987-1992 model, (not made to handle masses of power) i've had no end of engines come through where people have tried to stick this and that on it, it's gone splat and i've bought it to recondition it. i'd go as yamaha intended, grab the 28mm mikuni carb off a 4hw tzr, and the inlet and reeds to match (if that isnt what yours is running at the moment) IN MY OPINION, DO NOT RUN A HIGH COMPRESSION KIT ON THIS BOTTOM END, IT WILL NOT HANDLE THE POWER, AND IT WILL SH*T ITSELF UNDER STRESS, IT JUST CANT HANDLE IT.
the ram air filters may sound great (that great sucking noise!), but can damage reliability due to the lack of controll of airflow, ideally you'd need to rejet from summer to winter and visa versa due to changes in air density and temperature through the seasons, NOT FORGETTING THEY GET SODDEN WHEN IT RAINS IF ITS NOT PROTECTED! (which isnt the case as much with a standard airbox) but it's a long debate that'll never end, airbox or not airbox or not..... each person prefers their own, but the gp's all use airboxes....... lol
for both engines, tzr125r, and tzr125rr, the best thing you can spend your money on is the exhaust system, and carb, maximum power gains, in the rev range you want it, with only the time consuming task of re-jetting to suit.
that or send the barrel to a well recommended 2t engineer, and tell him what you want from it!
dont know if this helps, but i fancied a ramble on about something, and seeing as the sachs uses the yamaha engine, i thought this seemed a good place to do it!
let me know if i'm wrong on anything, i'm still learning, but after stripping a lot of tzr engines this year, i'm getting there!

last but not least, a little note on bhp, this whole 33bhp marker that everyone chases, it's a very challenging target to find, seeing as even a rs 125, only produces 27-29 at the wheel, the 33bhp claim is the reading taken from the crank! power is lost throught the transmision and the drive gears/chain, and then the tyres, i've seen three brand new bikes from aprillia, straight onto a dyno out of the box, they ranged from 26-28.2 bhp at the rear wheel. and that was back in the day when they were the fastest thing a crazy teenager could buy!
the very very best and top flight of the superteen 125 bikes are only running at 35 bhp, and the top flight only make one race before needing a full rebuild, if they went past arond 35 bhp, the bikes wouldn't even finish the race before falling apart through the strain.
anyone who claims 33bhp at the wheel, show me/everyone the dyno readout, if you got the 33bhp, you've worked hard, tuned very well, spent a lot of money, and got a very fast bike, be proud

Thats useful information, but i would not trade my 3bl cylinder for one of tzr, the only one that i would trade for mine's is tzr's 2rh, the one that is an hexagon! Thats one of the cylinders that is plug n play on dtr bottom engine that gives you more power.

The only thing im saying about the exhausts is that they are all restricted in some way... if the guy that made my exhaust made one for each model that you were saying, it would be better than the stock one. I know dtr with far more that 33 bhp :) and mine only has a 32mm carburator, and the exhaust, when i buy the twin air and boyesen reeds and tune the bike up ill bet ill have at least 30 bhp :)

NEV · Guru

Nope the early standard 3mb exhausts weren't restricted whatsoever, it was the later standard 3bn exhausts on the DT's that were restricted and had to be opened up to take the baffle restrictions(half-moons)

miguelNS · DTR Respected Member

NEV wrote:
miguelNS wrote:
But i dont have a tzr engine and having an exhaust that isnt made for your cylinder measures is having something that wont work right
You'd be surprised how similar a tzr and a dtr engines are, difference is mainly gearing, and 3 gears are the same if I remember correctly

They are similar but not the same, starting that dtr bore x stroke is 56.0 x 50.7 mm and tzr is 56.4 and 50 mm. theres difference there to start. The gearbox isnt like you said.. if you put a tzr gearbox on dtr you dont know how much you have to increase the transmission, believe me. And there are more diferences, electronics and ****...

miguelNS · DTR Respected Member

NEV wrote:
Nope the early standard 3mb exhausts weren't restricted whatsoever, it was the later standard 3bn exhausts on the DT's that were restricted and had to be opened up to take the baffle restrictions(half-moons)

But you didnt get my point. besides restrictions or not, these hand made exhausts increase the power of the bikes :) there are errors that yamaha made building some things, and this guy "rxpessoa" as you can see on the little plate of the exhaust corrects little errors that are made or were made. Like him there are many in portugal, were we call them "preparadores". In english by translations is preparers but i dont know if thats the term you use xD

miguelNS · DTR Respected Member

wazup mates? ive seen that this thread had no movement whatsoever!!! I made some more changes to the bike, i have changed the rear tire and the exhaust also!! The other one was super powerful bue i had no power in low revs!! the tire is a bridgestone battlax bt021

Calum122 · Guru

Very nice

miguelNS · DTR Respected Member

thanks bro

Energized · DTR Legend

Yo carlos bro! nice one mate glad you got a standard looking xpanny back :P what is your top speed and gearing?

miguelNS · DTR Respected Member

i use 16-50 and its a bit short... its arround 150 km/h the bike is full stock, the onlly modification is the bigger carburatos, 32mm

Energized · DTR Legend

sweet :D which carb you use and was it worth getting bigger carb?

miguelNS · DTR Respected Member

it's one of the best modifications you can get on dtr... makes the bike much much longer!!! its a oko 32mm

Calum122 · Guru

Yes but there isn't any aftermarket inlets to take them. Or aftermarket carb boots. So you'd have to bodge it in there.

miguelNS · DTR Respected Member

im using the standart inlet... til 34mm carbs you can use it!

Energized · DTR Legend

oko??? And what do you mean it makes the bike longer?

miguelNS · DTR Respected Member

almost like you change the transmission, it makes the gears longer!!