De Restricting my DT125R

[Airhead]

This thread should become a sticky! Everytime i find the time to get on here its always up there! Was there any kind of noticable difference from the snorkel? Also, it reminded me of the DTR.net sire that talked about cutting the rubber from the inlet manifold. I Cant remember if we've discussed this yet.

I covered the inlet in post #64 Andy, I dont think chopping it all off is a great idea...whats the point? The shape of the moulding diverts the flow in the right direction. I opted for some modification though and ended with a shape more akin to the YZ and TZR bikes.

I dont have that annoying induction roar now with the snorkel on so i'm happy, as for performance...probably not noticeable but all these little bits added together have improved the bike no end...not finished yet, just gotta tinker more

[AndyDtr08]

I covered the inlet in post #64 Andy, I dont think chopping it all off is a great idea...whats the point? The shape of the moulding diverts the flow in the right direction. I opted for some modification though and ended with a shape more akin to the YZ and TZR bikes.

I dont have that annoying induction roar now with the snorkel on so i'm happy, as for performance...probably not noticeable but all these little bits added together have improved the bike no end...not finished yet, just gotta tinker more

Ah, yeah i remember now. Could have just looked through...laziness i guess! Yeah i was a bit skeptical about that but just wanted to find out if there was somthing i wasnt seeing. I personally am keeping mine standard, other than easily reversible things like earthing the wire. Looking to sell it pretty soon so wanna hold the value.

Hopefully getting a job in london within the media industry so im going to be taking my full bike test and getting somthing i can commute in on. Have had my heart set on an rd350 ypvs before these new plans came about and now im not sure if i should get a fazer 600 or somthing a little more suited.

[SUPER DTR125]

hi there oldgitonabike!i beening trying to get the snorkel from a dt230 lanza but no luck,would u please let me know where u got yours from???many thanks.

[Airhead]

hi there oldgitonabike!i beening trying to get the snorkel from a dt230 lanza but no luck,would u please let me know where u got yours from???many thanks.

I got it from here

Part number 4TP-12237-00

Any Yamaha dealer should be able to get it though, Granby and Fowlers are always a favourite recommend

[SUPER DTR125]

fantastic!!tomorrow morning will try get one

[d4ng3rous-d4v3]

hello. um do any of you know whether my powervalve cables need to be crossed on a 2001 DTR because when i had my powervalve running with the cables uncrossed, it would hit the band patheticly and would only top out at 65. so after loads of thought and time i decided to pin it open(with servo not working) and lost no bottom end power and it now power wheelies when it hits band and will do just about 80 at a scream.

then i was playin around with the ypvs and fully closed it(with servo not working), and when i pulled away it was a powerhouse untill 6k and it wouldnt go further.

unforantly i snapped a bit of plastic on the servo which holds one of the cables in place and before attmeptin to fix it, i would like to know whether or not my cables need to be crossed, or whether or not i might have the powervalve in correctly.

if anyone can help, would be very greatfull:)

[Airhead]

No not crossed Dave, have a look at post mumber 31 onwards in this topic for PV setting.

[d4ng3rous-d4v3]

No not crossed Dave, have a look at post mumber 31 onwards in this topic for PV setting.

okay dokay, i was going to look through the whole thread, but one to many posts to read them all. thanks, i'll have a ganda

[ging]

Just the bevelled one in the 125, the other straight one came from my 175. I doubt your 125 has this restriction because no one would put up with that for more than two weeks

has exaust got one of these in dtr 125 02 plate

[d4ng3rous-d4v3]

Sorted out my PV today.

on removal of the pulley and exhaust i found it to be in the restricted position.By sticking a finger in the top of the exhaust port it could be felt that there was a hollow groove between the port and the PV. This is because the PV needs to be turned slightly more and will then be a smooth passage through port to cylinder with the pulley aligned with the 4mm hole in the cylinder. There are two possible positions to mount the pulley onto the PV, hopefully the pics will make it clearer.

Pic 1, Pulley removed and this is the position as found (Restricted)

Pic 2. Back of pulley showing how the PV would sit in the restricted position.

Pic 3. Back of pulley showing how the PV would sit in the un-restricted position

I can report a definite improvement now and the bike is much more willing to rev freely.

Cant give it beans yet as due to still running in so revs not going much over 6k at the moment.

DEP silencer is on order and a 250 main jet. I believe standard is 240.

hmmm ive looked at my powervalve pulley and where it sits, and on my dt it does not have the diamond shape, instead it is of a rectangular shape that fits perfectly into the back of the pulley. :S

[Airhead]

hmmm ive looked at my powervalve pulley and where it sits, and on my dt it does not have the diamond shape, instead it is of a rectangular shape that fits perfectly into the back of the pulley. :S

Then yours can not be restricted at the PV.

[d4ng3rous-d4v3]

Then yours can not be restricted at the PV.

it was though :S... but once i rebuild the whole engine, i'll play about and find out lol...fun :|

[Airhead]

it was though :S...

? I dont think so, unless someone had it completely upside down, that would not be a restriction per-se, just incompetence

[AndyDtr08]

? I dont think so, unless someone had it completely upside down, that would not be a restriction per-se, just incompetence

I thought that was Yamaha's attempt at a restriction. They just put the valvle in 180 degree's and didnt fit the servo kit so it just blocked a lump the port of constantly to comply with regulations in britain. Then you could buy the servo kit from yamaha for around 200-300 quid, or just losen then valve, turn it and tighten. My brothers early DTR was set up like like, i've just turned the valve to the best position for a compromise between the two extremes.

[BEng]

I wasn’t sure whether to add this post here in the “Project” section but I thought I would add it here as all of the information is about tuning a DT125R and not really about build my DT125R. Anyway I have copied the following few paragraphs from the new members section, so sorry if you have seen some of this before. But there is some new stuff, and I will be updating the forum as I find out more info.

So the work I have done on my DT is as follows. I have from the bottom up, replaced the main bearings and all the seals. I have matched the transfer ports in the crank cases to match the gasket and barrel, smoothed out some of the rough edge and matched ports to flow with the barrel. Polished the crank cases around the crank shaft area, I know this doesn’t do much but I like smooth surfaces and it didn’t cost me anything but my own time.

The reed cage already had some sort of after market fiberglass reed. I don’t know of the make, but there was nothing wrong with them, so I used them. These reeds were a lot longer than they needed to be so I moved the reeds back to the mounting face and re drilled the 3 mounting screws, this I believe will do three things. a) Make the end of the reeds move to just 1mm passed the end of the open hole, where I wanted it. It now means I can open the hole out closer to the mounting face which will increase the intact area. c) The reed stops are now be mounted in the new position which means two things i) with out bending the stops which I believe you should never do, it will increase the amount the reeds open relative to the reed block, which will increase flow thorough the reed block, it will move the reed stop out of the way on the rear transfer port which it covers quite a lot. On the rest of the reed cage I smoothed out the opening and opened up the holes so there was open only 1mm contact around the hole for the reed petals.

I had to have the barrel rebored because it was damaged, so it is now 57.5mm. I brought a good quality piston, but still had to clean up the inside of the new piston the remove all the sharp edges. I added a nice 2mm chamfer to the bottom edge of the piston to help stop the oil from being removed whilst the piston is on the downward stroke. To finish off the piston I polished the top.

On the barrel front, I matched the transfer ports to the newly modified crank cases and gaskets (I know I said gaskets, I will come to that in a bit). I flowed the bottom edges of the transfer ports, and smoothed the whole area. I widened and slightly raised the exhaust port. This made the shape a lot better, from a square to an oval, this will help increase ring life. I then matched the power valve to the new port shape and smoothed the rest of the port, and finally polished the port. Next I measured the height I would need to arise the barrel by to match the piston at bottom dead centre to the bottom of the transfer ports. This worked out to be 1.7mm with one gasket. As a gasket was .5mm I then made a new gasket out of metal, which was 1.2mm in thickness. So now as a base gasket I have a metal plate of 1.2mm sandwiched between two normal base gasket. After I had done this I then measure the squish band clearance. To get down to the 0.9mm I wanted, I had to machine 2.1mm from the top of the barrel.

The cylinder head I’m using is the 3MB type, apart from polishing the squish area, I didn’t need to do anything else with it.

I have installed a Pipercross air filter, because the bike had no air filter at all. It already had a Dep front and rear box. I have also fitted the power valve control motor.

Although the bike is the 90MY the wiring loom is from a later bike, not sure of the year, as I brought the loom off EBay. When I have the bike "run-in", I will let you all know how it is going.

So far I have done 250 miles and all is going very well. The bike is pulling very strong in all gears and will pull 10.5k rpm with out any problem, even in top. I have not let it go anymore myself, but I’m sure it would if I let it.

Now I’m not sure about what the gearing is supposed to be on the DT so any feedback would be nice J. I have been looking through my Haynes manual and on the net/forums and it seem to be that 88-90 should be 17/55 and 91 onwards used 16/57. At the moment I have the 16/57 combination, but I have ordered a 17 and 55 sprocket. I know it needs gearing up, but I don’t know how much, I have a feeling it will need more but until I try the 17/55 combination I won’t know.

Another question I have is, what speed should I see, for what revs. I’m running standard size wheels and tyres, front 2.75-21 and 4.10-18. At 10k rpm in top gear my speedometer is showing 80mph, which works out to be 8mph/1k rpm, does this sound right?

O and something else, in previous posts there is lots of question about the reed switch in the speedometer, and what to do about the wiring. I have a set of old DT125R clocks which don’t have the reed switch so the wires which would go to the reed switch are connected to nothing. And my bike revs to the red line without any problem and goes faster than 65mph which lots of people say seems to be a problem. So I would conclude from this that the just need to be open circuit and not shorted to earth as some people have suggested.

Vince

[AndyDtr08]

I know we've discussed the difference between 3MB and 3BN cyclinder heads before but i'd like to bring it back up. I'm clearing all of my old DTR parts from the loft and listed a 3BN head on ebay a few days ago. Just checked it last night and this is what i found

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=270781212564&ssPageName=STRK:MESELX:IT

Why is it worth so much money if this is the one that actually restricts? I read a bit about squish bands and everything seems to point to the fact that they increase performance. Any one any other ideas as to why it would have reached £77?

Andy

[Airhead]

I know we've discussed the difference between 3MB and 3BN cyclinder heads before but i'd like to bring it back up. I'm clearing all of my old DTR parts from the loft and listed a 3BN head on ebay a few days ago. Just checked it last night and this is what i found

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=270781212564&ssPageName=STRK:MESELX:IT

Why is it worth so much money if this is the one that actually restricts? I read a bit about squish bands and everything seems to point to the fact that they increase performance. Any one any other ideas as to why it would have reached £77?

Andy

wow I cant explain it £77 for that manky looking thing

sometimes things just fetch silly money and this seller is very lucky indeed to have got this amount I think.

[AndyDtr08]

wow I cant explain it £77 for that manky looking thing

sometimes things just fetch silly money and this seller is very lucky indeed to have got this amount I think.

Yeah i didnt bother cleaning it, just started snapping away at all my old bits and listing. Just need the space rather than the money. Hope they honour their bids. All the money from these parts is going into the DT200WR. I sold the bottom end of this engine to someone on saturday for 72 quid. Never expected just the head to sell for more! Ha!

[satelliteone]

hi guys, i owned a dtr 125 r 2003 model and de-restricted it. 90mph and full power all the way up the power band.

The speedo has a reed switch, pull it out, away from the clock face, tape it up and leave.

exhaust, either go down the full DEP route, but i didnt like the dep. too toppy for me, 8K power band..mmmm

Use the original, but cut the restrictor out of the flange, like in the first post, and then cut along the seam in the expansion chamber, open up the zorst, knock the two bits of metal "wind breakers" out. TIG reweld the two halves back, in perfect postion again.The original zorst produces better power IMO.

some of the newer RE`s and X DTR`s have a carbon CAT in the front of the pipe. this needs to be taken out too, or just buy an older zorst.

carbs..mmmm.. standard is 28mm flat side or even older 90`s is a 26mm mikuni`s , just make sure the jetting is perfect.

if you can, find a TZR125R Dellorto 32mm with the inlet rubber + reed block that will make a huge difference.

The TZR125R 4DL model has the shares the same engine, just the CDI and the carb + exhaust makes 33HP

the standard cylinder head is designed for lower compresson, change it also. to say a 4FU, the compression will come up.

http://www.ebay.co.uk/itm/Yamaha-TZR125-93-97-DT125-TDR125-Cylinder-Head-13815-/280716578375?pt=UK_Motorcycle_Parts&hash=item415c030e47

hope it helps..

[monster_ben'ergy]

Hi I have a 2001 dt125r with a full 'big one' exhaust system replaced battery spark plug air filer, after reading your pinned topic I wrapped up my reed switch and pocked it through the hole below so it's dangling just above head light but it's only about 3 inches from it's original position as it wouldn't stretch to far, just took it down road and still won't go over 55 mph, do I need to stretch the reed switch further or anything else, my acceleration is really good just soon as you hit 50 ish it just stops pulling.  

Ben