DT125R FORUM

@theportingmaster
that's looking real good mate, certainly way better than my porting

@calum I havent really decided that yet, i want to be able to run the pv but I'm not sure how to do it with the auxiliaries in a good way, ideally id like the ports to stay closed and open up with the rest of the valve, idk how well that will work tho so I might just resort to having the open all the time

been a while, ive just recently started doing some work on the bike again, took a long break over the winter, you lose the will to work on the bike when its negative degrees in the garage.

Ive been getting some stuff going this past week, I was able to go over to my neighbours company/workshop where he had a lathe i was able to use. So I threw together an adapter that is slipfitted over the cylinder skirt, which then centers up in a simple 3-jaw chuck lathe, I did this cause I didn't have access to a four jaw, but that's ofcourse the preferred method to go. I then skimmed and bored the barrel, still have lots to go cause I think a piston had exploded in that barrel before so there's a lot of material missing over the exhaust port.

https://i.imgur.com/LhPCUF0.mp4

https://i.imgur.com/usIIdnO.mp4
Some vids I took at the lathe.

I also just last night finished up making a port map for my 3mb barrel, I later printed it, cut everything out and used it as a porting guide

As you can see I added some 8mm auxiliary exhaust ports.

I then just started porting, the only tools I had to use was a normal dremel with a flexshaft and some carbide and diamond burs aswell.

Ofcourse its not even close to a perfect port job, but it being my first time without and real porting tools I'm really happy with the result, its not finished yet, the ports need to be cleaned up, barrel needs a rebore which ill do in the lathe this week and the exhaust port needs to be polished cause it got some dings from the dremel. I went conservative with this first iteration, they open at 188 degrees, my main port opens at 200 degrees. Its just a test and if they need to be higher ill raise them a tiny bit.
I then also need to attack the power valve to get passages for the gases to flow through that aswell.

Some other stuff I've been working on is an airboot for my 32mm carb so I can use the stock airbox, the opening for the carb is 55mm compared to the roughly 38mm stock carb and boot. No matter how much heat or force used it didn't fit.

My tacho fixture on the case had also been stripped so took an hour to mock a new model up in solidworks so I could 3dprint

I was also able to pick some wr426f forks up for free, however the shape they're in isn't the best, the aluminium has corroded and pitted all over the fork tubes, its nothing deep tho so its only visual, so whenever I get a front axle for it and get the bearing cup made I'm chucking them on aswell

@spookdog thats a good idea tbh, i might try and make up a design and see if i could get a quote on how much it would cost to have one cut compared to 10-15 cut.

@declan
I imagine you could get one plasma or water cut somewhere, i have no idea about price but i feel like it would end up rather expensive with a one off order like that

@ninja
Thanks for a long and well written answer! Thanks for clearing everything up, however have u looked at the old cr125 brake disc for the front? It looks very similiar to the dtr, however im not even sure if bolts etc would line up as ive not been able to measure anything yet.
I guess ill just have to try and upgrade everything else and leave the disc stock if i cant find anything that will work.
Im hopefully going over to 426f usd forks soon but im however sticking to the stock dtr wheel sadly

@nottsbiker
i see, do you know how much that place takes to make disc?

@SpookDog

Im already looking at other brake calipers, found some 4 pot one that look rather okay, they're from aliexpress however, I know that might just be the stupidest place ever to buy anything brake related, however, I have seen some reviews about them and they seem fine. The main thing of me wanting a bigger disk is one ofcourse I want more stopping power, but also I relacing my dtr hubs to some 17" Sm wheels and the stock brake disk might look rather weird paired up with sm wheels, maybe not I'm not sure yet.

@declan
Ive not seen these wavy disks ur talking about, do you have a link?

@declan
No, the dtx has the same hub as the wrx, very different looking compared to the Dtr hub

@declan
Im talking about the brake rotor itself not the caliper. Im looking for a bigger brake disk that fits on the standard DTR front hub

@declan
Yeah im pretty sure that front rotor is a 320mm one, but would it work well to make an adapter plate for the brake disk itself?

What brake disks fit the original dtr front wheel hub? Is there any 320mm disks available?
Does front brake rotors from any other bikes and models fit? Ive seen some versions of the cr125 rotor and it looks fairly similar, but I'm not sure, so If anyone has any knowledge of this its greatly appreciated!

@ninja lovely mate, thanks a ton!

@calum
Yeah, do u have a clue about the width aswell cause thats what im struggling to find

Like the title says, both front and rear, they are 17x??

@jonne123
Id say just start with measuring everything, and then start and get everything to the manufacturers specification. Maybe someone in the past added thicker base gaskets so your a couple 0.1mm+- over recommended measurements from yamaha. Just get everything back to standards so you have a good place to go from if you want to continue modifying, but you will probably be happy leaving it as is after that tbh.

Im no dtr cylinder head genius but i know that the 3mb is the unrestricted head compared to the 3bn, idk how the 3mb compares to the 4fu or 3mbP however

Might also be possible to just move the stator and pick up assembly as a budget way of changing ignition timing. Im not 100% sure now and you should do your own calculations tbh but when i measured it myself the number i got (I think) is every 0.7mm of rotation of stator is equal to 1 degree of timing. you would just have to slot the screw holes using a dremel or round file.

@declan i dont have any of my own experience so im not sure, i saw a guy on facebook use a cr inlet to make his carb fit, he only mentioned that the reed stuffers where the only problem and nothing of the actual bolt pattern, but like i said i lack any personal experience in that matter

@DylanDT219
I can look at it a little tomorrow but i can promise nothing, im still just an apprentice when it comes to the 3d designing but ill give it a look

@dylandt219
If u have access to a 3d printer, or friends with one or somewhere u can get stuff 3d printed, that route would be better to go if u ever wanted to revert back to the old carb, im guessing youve already tried loads of heat to slip the carb in to the standard inlet?

Ive otherwise heard people saying that the Cr125 inlet and reeds have the same bolt pattern but you will have to be creative about the read stuffers.

I could try and mock up a cad design in solidworks if u would be able to go the 3d printing route if u would be interested in that yourself. However im no cad wizard so i cant promise anything

@theportingmaster
Thats a really good price, what shipping company were u using??

@dtr-nsr
What is the length of the spacers u put in the forks??