DT125R FORUM

@kepirok I haven't ridden it in years! I do really want to though, it's a great bike

@kepirok Probably lost to time now due to Photobucket and Imgur. But everything is documented on my build thread and I made a YouTube video of the build, so you can piece the two together there.

https://dt125r.co.uk/topic/15/the-leviathan-project?_=1776597285894

https://youtu.be/jZ1C_xCmqWg

That's so cool!

It's been ages since I have been on my DT. I ought to sort the bits out on it and get it up and running again.

My ETX is close to being done as well and that thing will rip when it's finished

Hello and welcome to the forum!

Tidy looking TDR you have there

@hotshot-iii Always heard good things about the TDR250. @scrimsmustang Used to rate them as well.

Oh awesome! Congrats on the bike. I've had mine now 16 odd years now!

Some great advice here, but I'll just chime in with some alternative idea for food for thought, but it doesn't negate the great advice we have here.

Many years ago, I went down the TZR Belgarda route, which effectively ran a DT125RE engine, just modified porting. As a result, I ended up using the carb from that bike, which was a Dellorto VHSA 32mm carb. These are probably easier to find as they're used heavily in the scooter community.

I've never had problems with that setup, but I am not convinced that the bike is that rapid (despite all the mods I've done), but maybe I just got used to it.

I just run an NGK cap for mine.
https://www.pjme.co.uk/acatalog/NGK-Spark-Plug-Cap-Racing-Red-1550.html

Pretty sure I run an NGK lead as well to be fair.

So I don't align the powervalve with the hole (partly because my exhaust/valve have been ported so it probably isn't right anyway. You did right by aligning flush with the exhaust port. I'd just focus on that, take the exhaust off and align it with the exhaust port. Flick the ignition on and off a few times to make sure the cables don't realign.

If you want a quick way to diagnose your problem to get you a steer in the right direction then I'd do this.

1. Align the powervalve flush with the exhaust port
2. Disconnect the powervalve servo
3. Remove the carb air filter boot (eliminating the airbox)
4. Run the bike with no air filter

What this should do.

Remove the powervalve will stifle bottom end, but 6k+ should shoot off like a rocket.

Eliminating the airfilter removes any restrictions that might be present in the air intake tract. Whilst not ideal running without a filter, it will be fine for a short space of time. Unless a stone flicks into the inlet you'll be fine.

You should now be running the bike quite lean (so avoid prolonged wide open throttle). The bike should run better now than ever.

If it runs worse, it tells you your jetting is too rich. If it runs better then you know that you need more fuel. If it runs the same, then you know the problem lies elsewhere.

I am expecting it to be the latter, I'm expecting the problem to lie else where, but ruling these items out first, means we can then start to go more technical knowing that we've addressed the simple things first.

The OEM ones are apparently made by GPR or Tourmax.

One manufactured by Mitsubishi should be of sufficient quality, Mitsubishi supply into Yamaha for a lot of other parts these days.

Can you link the one you're looking to buy?

Presumably it's this one:
https://yambits.co.uk/dt125re-ignition-coil-mitsubishi-japan-p-222065.html

Yambits is a quality website, so should be reliable and Mitsubishi is not going to mess about with subpar coils.

Hi John,

Sounds like a lovely little time machine you've got there.

Cracking bike and very very reliable, if it's not working, then it'll be something very simple and I am sure we'll be on hand to answer any questions you may have in an attempt to get you on the road again.

Definitely go the OEM route for sure.

I must admit, I don't bother explicitly bleeding the pump anymore, since it's an open system anyway it should self bleed. I.e. it's not a sealed system.

If the pump comes off, I usual stick some two stroke into the fuel for belt and braces.

But I have always ran clear oil lines as it's better to be safe than sorry.

The coil was used on a large variety of machines and can be ordered online:

https://www.motorcyclespareparts.eu/en/yamaha-parts/3rwh23100000

Ultimately, it'll be a fairly generic part and I'm sure one off the DTR would work fine, the basic engine is the same, but there appear to be some subtleties, so best just stick to the part number described.

Definitely don't buy an aftermarket coil they are useless!

Go OEM or don't bother. I'd be surprised if it is the coil, but given the availability of the bike, finding another one shouldn't be too tricky. I bought a brand new genuine one not too long ago as I made the mistake of buying a Chinese one and it causing all manner of problems.

Well, the Mito engine is highly strung. The Mito runs rings around the DTR, but as a result they're a lot more fragile.

I had the same thing with my ETX, absolutely battered bike, but it's in such a low state of tune that the engine was crisp, almost criminal to rebuild it.

#PotentialHandGrenade

https://www.youtube.com/shorts/0KlaU_adlWg

This was the state of my Raptor piston prior to me rebuilding it. Engine was running absolutely tip top prior to dismantling it. But this was a literal ticking time bomb.

Yeah, I used a Honda CR85 Apico one on mine. I though the YZ 125 ones didn't fit.

Go with the 210 main jet, do a plug chop and adjust to suit.

The CDI on the 2006 DTX (at least in the UK) is restricted. So you won't be getting full power until you derestrict it, even then the performance is still stifled.

Biggest upgrade I noticed to overall performance was a Zeeltronic ignition system.

Vastly improved the performance on my DTRE.

Are you using a genuine coil?

I had something very similar with a Chinese 'race' coil. Took me absolutely ages to get to the bottom of as I rebuilt the whole bike from the ground up and the coil was one of an assortment of new parts.

So I am very wary now of aftermarket coils.

Was it doing this before the exhaust change?

Yes please @rallyfinnen

I'll be watching this intently

Always wanted a Lanza personally.

Will love watching this progress.