DT125R FORUM

You don't need a battery but you'll want a battery. Yeah, looks a bit of a basket case that bike and you're asking us to make wild guesses when it could be anything. You've not running a snorkel, that engine does not sound crisp at all, you can tell it's swamped with air and it's struggling. Without a battery you're relying on the generator making sufficient power to do all the lights and make 20'000 volts at the spark plug lead, coupled with the poor wiring, bad earths and the second rate coil, it's no wonder it's not running right. You need to get yourself a battery. Sort the wiring out Get a genuine coil on there Get a genuine snorkel fitted https://ebay.io/m/cHVjjv Make sure you got good grounding from the chasis to the negative terminals. Search on this forum for the wiring diagrams as there are many different grounding points, different for different years, so ensuring you got the wiring for your model will ensure you capture the grounding points. Ultimately there is not a lot to these engines, but you have to have the basics done right, otherwise we're stating into the abyss trying to help you.

Probably worth mentioning, as you can see in the background of this photo, I have managed to acquire a fully supermoto setup for this machine as well. These come off the Aprilia MX 125. Since I'm running an MX rear end, that should be simple enough to swap out, but the front end shows some challenges. The MX125 front wheel uses a digital speedometer, so swapping out the front end means losing the speedo. Instead, I managed to find a brand new old stock MX front rim, and I've also managed to source an RX125 front hub, so I will look to lace the RX hub onto the MX rim, thus retaining the original speedometer configuration. The rear wheel is in poor condition, the hub has snapped in several places, but I managed to find a brand new old stock MX rear hub, so the plan is to lace both wheels and have an easy to swap out setup for both road and trail riding.

Oh. So there are no dead cones in the pipe? Just the cat? Because in that case I think removing it is quite straightforward and might not require cutting it completely in half. It might be possible to cut a window in the pipe and break the cat apart

@Yaya97422 Vert/noir

Hmm I did already, anything else I should check?

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Thanks for the reply’s gents but I’m afraid I’m going to ask more questions haha.. I’ve got some main jets on the way as I think the problem is it’s not getting enough fuel, I changed it from the 210 that came on it to a 260 to match the 5dp39 buts it’s still too lean, I was going to just revert back to the original set up but it turns out I’ve lost the original 5j25 needle and they are like rocking horse shit, I can’t find one anywhere. So if that doesn’t work I’m on to a new carb. Taking onboard @calum suggestion I’ve been looking at the Dellorto VHST 28mm but wanting to stick with a MIKUNI I’ve also been looking at the Tm30. Now here comes the questions, Given the Tm28ss has slanted intakes will a carb like the ones mentioned fit okay as they have straight intakes? Is the tm30 a valid option? Is there a baseline/recommended setup with jets and needles for the VHST and TM30 for the Dtr ? You’ll have to bare with me this is the first bike where I’ve had to deal with carb issues and I’ve been thrown in at the deep end

Hi, thanks for the help it's a 1998, the one I have goes into the intake boot with a peice of tube which I would guess and say is around 250mm in length then the chamber sat on top. Will get some photos tonight

@Calum yea the thing is that I have heard that the German version uses a diffrent cdi from other regions and I haven't found a guide on how to derestrict the cdi on a German one

There are wiring diagrams and manuals around on this site. Try searching using the built in search. Another great tip is using Google In Google search engine do site:dt125r.co.uk wiring diagram 6 wire and let Google indexing do the heavy lifting.

I can't say I am very familiar with thise pipes sadly. I have been away from the tuning scene for these bikes for many years now. It's been years since I've even ridden my DT to be fair.

Zeeltronic easily the single best upgrade for my DT

Hey! I know I'm late but I have a 1988 Yamaha DT125R swiss edition, which has the 3DD code. I checked the parts diagram and the 3DD-14610 pipe is originally the 1988 swiss edition pipe, which is supposed to be heavily restricted. I'm pretty sure mine only has a catalytic converter, I was hesitating about cutting it open but now that I saw your pictures I think there's no reason to do so. Your pictures look like the pipe really only has a catalytic converter. But I must ask, were there any restriction cones or washers that you didn't take a picture of? Thanks!

I meant the wiring for the bulbs. Thank you for the picture, the problem was that the diagram I found showed that the brown wires aren't supposed to be connected (brown from the thermometer, oil bulb, neutral bulb), mine showed that the thermometer needed to be connected to the oil bulb and that the neutral bulb brown needed to go straight into the 6pin connector, without connecting to the oil bulb or the neutral bulb. I didn't understand that but the diagram you sent made everything completely clear, thank you!

@Calum said: You can measure the coil to see if it's within tolerance, what I was finding was that from cold it would work a treat, but once under load and warmed up, it would fail to fire above 4k RPM. Okay good to know. So even my measurements looks okay to me I thought about that it might not be okay under load anymore. But I didn't want to manipulate any plugs just to measure under load. @Calum said: I've had this before with a faulty ignition coil. These can still be bought brand new from Yamaha and I highly recommend going for genuine coil over an aftermarket one. The aftermarket one I had led me on a wild goose chase trying to figure out the intermittent faul Do you have any link or shop? Thanks