DT125R FORUM

I've got an update. It's been a while since I've got a new stator but there is some inconcistencies in the service manual. Before I mentioned that the resistances reading match the manual. But that's regarding the values mentioned in the troubleshooting section. I'm referring to page 8-11 in the ignition section point 7. source coil resistance. There they mention 192-288 ohms which was where my old coil was within. That's over both source coils if I'm not mistaken. However the new coil has different resistances. And those actually match the values in the manual on page 2-8 general specifications - CDI source coil. There they specify both resistances: 730 and 600 ohms +-20%. So it seems there is an issue in the manual but also my old stator matches the troubleshooting value and the new one the ones in the general specifications... Regarding the old measurements. It turned out that the voltage in the traces above are the same for the two coils in series as well as for the small one alone. The big one actually outputs 0V so there is definitely a short under load in the bigger coil. Regarding the new coil. I measured both independent and I got a sine wave with 90Vpp (peak peak) for the smmall and for the bigger one around 460Vpp. So way more than before. If anyone is interested in the scope traces I can upload them as well. So I decided to just give it a try and it worked just fine and I've got spark again!! Buuuuuut.. the first test run, after roughly 50km I lost the spark again. Turned out that the stator got that hot that the solder liqifyed and all the cables detached from the source coil.. Also the stator tooth touched the flight wheel at some point since I saw some scratches. So I thought that's the cause why it overheated. So adjusted everything a bit and resoldered the cables and it worked for some time now without scratching and overheating. Until yesterday.. after some time going up hill the bike just turned off again and barely started again. I just made it home. Today I've checked it again and one cable was again detached from the coil. Now I'm thinking if the overheating was the root cause all the time which might also destroyed the old coil. But this leads me to the question what could cause this overheating. Could it be that the engine generally runs too hot? Does anyone have a clue what it could be?

Biggest update yet had a friend come over which has way more knowledge then me, original main yet is somehow too big for the bike so 240 is actually 1.3mm when we put main yet drilled to 1.2mm bike ran great but was missing a little notch we will have 1.25mm jet by eveninng and that should work properly will see still has small issues idling

I don't mess around when it comes to fueling. Just buy the genuine kits. I can't guess about how much I have spent on Dellorto odds and sods, but now have a healthy collection of bits should I ever need to jet my bikes I can breathe easy know it's all legit parts.

Due to the exposure that these bearings receive, it's recommended to grease them. The bearings themselves are exposed to a grease nipple so you should be able to just apply grease through their nipples directly.

As far as I was aware the catalytic converter was only on the RE/X and not the early model, for the UK at least, not sure about everywhere else. Either way, there is definitely some great points being raised here with cutting the window option, any debris that get sucked back into the engine could be disastrous.

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.

@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