DT125R FORUM

Hey everyone! It's been a while, but I've got some big updates

I've recently bought a used OEM carburettor, and the bike is running better than ever with the new cylinder at 57mm.

However, I've run into a new problem. If I leave the fuel tap open, it starts leaking fuel while the bike is off.
I've already replaced the carburettor seals, float and float needle, but the problem is still there.

Has anyone had a similar issue or knows what could be causing it? I'd appreciate any advice.

Thanks!

Sorry for going a bit off-topic from the original post once again.

I've recently come across a brand new 3MB cylinder and I'm considering buying it. Would I need to make any modifications to fit it on my DTX, or is it basically a plug-and-play swap?

Sorry if it's a basic question, but I'm still learning about these engines and I'd rather ask before spending the money. Thanks for your help!

I've been looking for a new cylinder, and I found an Athena 125 cylinder kit for the DTX and was wondering if anyone here has first-hand experience with it. How does it hold up over time with regular use?

In terms of performance, is it actually worth it compared to the stock Yamaha cylinder, or would I be better off rebuilding an OEM cylinder instead? The price is almost the same.

Quick update: everything is back together exactly as it should be, but unfortunately the problem is still there.

At this point I'm leaning towards buying a new head and seeing if that finally solves it.

I'm talking about the small tube next to the radiator cap. Where is it supposed to be connected? Mine just routes down to the ground and I'm almost certain it's always been like that.

The radiator is brand new (a high-capacity aftermarket one) and I got it about two months ago, so I doubt the cap has already lost its spring tension.

The strange thing is that it starts overflowing not even a minute of the engine running.

Sooo…bad news me and my friend put the head back together and it stills pour collant through the tube in the radiator…

Im lost here any tips? Im checking the head if they skim it right…

Yeah, fortunately it wasn't much warped.

I also took the carb to a guy who might be able to remove the stripped air screw. I'm waiting to hear back from him before deciding whether I'll need to buy a new carb or if a carb rebuild kit will be enough.

Sooo... a lot has happened, and it turns out things are worse than they first looked.

My Zeel finally arrived and I've already installed it. While working on the bike, I found that the cylinder head is warped and it's leaking coolant into the cylinder, so I've taken it to be skimmed.

I also found that the air screw on the carb is completely stripped and there's no way I get it out

I would say so. Is quite similar to the factory headlight, but it gives the modern look I was looking for, with a cleaner and whiter light.

Hello! Just an update I've tested the H4 LED and it works great

Thanks for the explanation, that really helps.

Would fitting a new gasket kit (especially base and head gaskets) potentially restore the correct squish/compression? or should I consider getting a new top end altogether?

I just want to make sure we’re looking in the right direction before replacing parts and not waste money on it.

(I realy dont know anything on the mechanical side).
Thanks once again!

I have another question
Ever since my bike came back from the mechanic a few years ago, it has had very poor low-end power and it never felt the same again. His excuse was that the bigger piston is heavier, but honestly I’m not convinced.

My DTX is noticeably slower than my friends’ DTRs/DTRE, especially in low RPMs. To be honest, I never went back to that mechanic after that. I already adjusted the YPVS before, but the problem still persisted. I also cleaned the carburetor and installed a new spark plug.

Right now I’m waiting for the new CDI to arrive so I can properly tune the power valve again and see if that changes anything.

Has anyone experienced something similar? Could the bad CDI cause such a big loss in low-end power?

Current setup:
Firebox expansion chamber
Firebox silencer (I think)
Original carburetor
18T front sprocket
51T rear sprocket

I live in the Azores, Portugal, and we don’t have the equivalent of the annual MOT test anymore,(only cars have it, bikes dont thankfully).

For my DTX, it uses an H4 fitting. I’ll test it when it gets delivered and give some feedback. Anyway, if it flickers, I’ll buy one like you suggested.

In the end, I decided not to install this headlight, ended up selling it.
Instead, I restored the original one and ordered a stronger LED bulb, which solved the problem perfectly.

This way I can keep the bike’s original look, which I personally prefer.

Here’s a photo of how the bike looks at the moment.
https://imgur.com/a/TcD2ypH

I ordered one with the connectors already installed
Everything went smoothly and Borut was very helpful throughout the whole process.
Thanks for the help guys!

Thank you guys for the help!
I’m going to get one, especially because there’s a plug-and-play option compatible with my DTX125. That makes the whole process much easier and avoids having to modify the wiring system.

I’m also running a full Firebox exhaust on the bike, so I was wondering if there’s any specific map/setup that I should get, or if I should just use the one that comes pre-installed. I don’t really know annything about CDI tuning, so any advice would be appreciated.

Hello everyone!
I need to replace my cdi and was wondering if the zeeltronic is worth the 300€ or is there anywhere i cant get it for cheaper.
Thanks!

Thanks!
I’ve had this bike since I was 16, and as you can imagine, I didn’t always take the best care of it back then. Since I need to replace the headlight anyway, I thought it would be a good opportunity to modernise it a bit.

For comparison, headlight. I’ve already had custom graphics printed for the new one so it matches the rest of the bike.

Hi everyone,
I bought a KTM EXC 2017 LED headlight and I’m planning to install it on my Yamaha DTX.
The headlight is currently with the shipping carrier. Is there anything I should know or check before installing it?
I’m looking for anyone with experience doing this conversion.
Any tips or photos would be greatly appreciated. Thanks!