DT125R FORUM

Have you earthed the green/black wire? Sounds like a restriction. Where is this PWK from? Is it a good quality carb? Although not the source of your problem here, as the demand/load on the engine increases, the reliability of the fueling also becomes more important. What might be fine in lower gears, presents problems further afield.

..and you need the battery too, not just the regulator. Forgot to write that

Thanks for that I ll go through it at weekend

@lucasg.03 I wouldn't go for a Pipercross air filter element to be honest, the stock one is perfectly adequate if properly maintained. Interestingly I once bought a Twin Air DT125R element which was a bit too small to fit over the plastic cage properly, meaning the base wouldn't seat where it's supposed to seal against the airbox body. I've also noticed some "tuners" on the DTR Facebook pages saying foam filter oil restricts power output. This is most definitely NOT the case; compare the surface area of the air filter element with the 28mm carburettor bore and there's no way a properly oiled filter could measurably reduce airflow. You're better off getting 3-4 Yambits air filters which are just as good as stock but half the price; then establish a routine for cleaning and re-oiling them. Put the clean oiled ones in a plastic bag and you can quickly throw on a fresh one after every wash/off-road ride. Jet washing the bike and not changing the air filter/going for a short ride is a leading cause of ruined crankshafts on two-strokes, you only need like half a cup of water to creep in to knacker the mains/big end. And a clean air filter cuts down on a lot of other aggro; you see it all the time with RC car racing. Because a 1/8th buggy air filter is only the size of a 35mm film capsule it starts to affect throttle response after about 7 minutes on a dry dusty track. A lot of the guys at my local club used to try and play the Big I Am Tuning Wizard by endlessly twiddling the mixture screws but all they were doing was reducing the flow of fuel to match the reduced air flow (i.e less power). Whereas changing the air filter = getting your hands dirty; no cool points for the Bloke Down The Pub even though it means the engine just runs well and doesn't suck dirt right through the day. Also the DTR airbox is poorly sealed where the carb-to-airbox boot meets the airbox (i.e downstream from the filter); it can be very helpful to seal this up with a product called Seal-All which is a petrol- and oil-resistant glue. You really need to remove the airbox completely to do this which means the shock needs to come out but this is easier than it sounds and you get to grease up the linkage bearings at the same time. https://yambits.co.uk/dt125re-air-filter-p-9241.html https://www.repairingproducts.co.uk/.../seal-all-gas-oil.../ [image: 53107628675_b20a021b82_b.jpg]

You can take a piece of soldering tin and bend it and stick it through the plug hole to get a rough measurement of the squish. If the solder is not pinched you can 'double twist' it to get a reading. This should give you an idea if it's the cause. A good value should be 1mm or slightly less IMO. You can find different thickness base gaskets in some places, like here: https://www.motorsportgoetz.com/Cylinder-Base-Gasket-03mm-Yamaha-DT-TDR-TZR-125

Just measure from the inside of the fork leg to the rim on each side, +-2mm should be ok I think. If you release the nuts on the axle clamp on the right side (if I remember correctly) and pump the front suspension up and down, and then re-tighten, it should not bind. If the seals wear out too quickly, I would check the surface of the fork tubes, so they are not damaged (pitted from rust, flaking chrome etc.)

Due to Imgur being blocked in the UK, I've had to rehost these images. Maybe I'll reorganise it at some point, but need to do this for all my projects :( [image: 706%20-%200I64IKK.jpg] [image: 707%20-%20kiFkXF0.jpg] [image: 708%20-%20NsOS570.jpg] [image: 709%20-%200SRgIcz.jpg] [image: 710%20-%20YRRwFIt.jpg] [image: 711%20-%204KsUVqJ.jpg] [image: 712%20-%20oRn2HN1.jpg] [image: 713%20-%20zJa3HdV.jpg] [image: 714%20-%202HICne6.jpg] [image: 715%20-%20ZkNBoOl.jpg] [image: 716%20-%20MMgf3Cm.jpg] [image: 717%20-%20sO4aX6K.jpg] [image: 718%20-%20fHYBkpE.jpg] [image: 719%20-%20ZrkY7k6.jpg] [image: 720%20-%206u25W4U.jpg] [image: 721%20-%20e2HmT5S.jpg] [image: 722%20-%20PxEEsO1.jpg] [image: 723%20-%20UmkUVAr.jpg] [image: 724%20-%20Dw0dU1d.jpg] [image: 725%20-%20hQnDI8H.jpg] [image: 726%20-%20w2mgN80.jpg] [image: 727%20-%20dyHdQ8o.jpg] [image: 762%20-%20faXVi2L.jpg] [image: 763%20-%20L5TZajj.jpg]

I'm sure someone here will be able to point you in the right direction. What we've been seeing in recent times are a lot of DTRs being imported from Europe, these can come with subtle differences, this may be the case here. This is the 3NC wiring diagram. [image: 52172141696_84e3b69382_b.jpg] I only have a Haynes manual so can't speak for what other diagrams look like. I have also hosted the workshop manuals here: https://dt125r.co.uk/topic/3258/yamaha-dt125r-200r-workshop-manual https://training.dt125r.co.uk/files/Yamaha_DT125_Workshop_Manual.pdf This may be useful.

@Calum maybe i could check the exhaust to be sure indeed, ill try that first. Some time has passed and it suddenly was gone but came back after a short while, very weird haha. The spark plug color is deer brown so a little rich but more for climate purposes because in Belgium the weather is so annoyingly unpredictable. But it would be weird if it was fuel related. Because it drives very well in alle the conditions for the past 300km. A have a bad habit to be a perfectionist so i can break my mind about to find the cause haha.

Lovely stuff, thanks a lot Hotshott! I’ve just seen that it’s a two cable powervalve servo actually that I need. I remembered wrong. Don’t know if that’s easier or harder to source will have a look today. Cheers for the info about cable pulleys I’ve already connected the yambits one I bought. Will review this when I get myself a servo from somewhere. All the best Dominic

Got it, thanks for your help everyone. Was planning to have a go but then had an episode and ended up in hospital. Now I'm back in the game.

@hotshot-iii hey, before assembly i adjusted the float height to 16-16.5mm according to the maintenance manual. I went through all ignition related cables and switches but nothing out of the ordinary. No corrosion etc... Also installed a genuine replacement coil and measured the primary and secondary winding just to be sure haha. The plug chop was done at 10k rpm. Did it a lot with mopeds to check if the main jetting was right. Today it was less hesitant to pull through so it went better when i just gave it full throttle from the go. This was after i finished the idle configuration with the screws. Steady +-1.6k rpm like the manual says and the air mixture screw is just about right. Temperature is very stable +-70 degrees celcius and its stay like that after driving almost an hour long. Im suspecting 2 things that are happening, correct me if im wrong haha. 1st thing is my powervalve that is opening a little bit to slow, i feel if they once open up, i can hear it and feel it and i can give them beans without any problem. Tohe other thing is maybe im running too rich in the lower rpms?

@reudtr88 The seller is right, the spacers and caliper bracket are narrower than the DT125R versions. The bench mock-up in the pics above comprised a 3ET DT200R swingarm, caliper hanger and spacers mated to a DT125R hub. As you can see the 428 sprockets lined up quite well (I also had to use a 3mm thick M20 washer between the caliper hanger and swingarm to get it as good as it could possibly be with the items I had to hand).

@Calum I hope you can find some time for that. It must indeed ride great with all those mods :+1:

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

Hi Calum, the OEM coil I ordered has arrived from Fowlers but the clear autolube pipe I ordered from e bay has not arrived. It is showing as running late when I check the tracking. I do not want to start the bike until the clear oil tube is fitted and bled so I am at the mercy of Royal Mail. Assuming the bike will run the only thing left to do is a couple of bulbs and then it should be ready for its MOT. I will fit a new plug cap similar to the one you show.

@Rallyfinnen ciao, grazie per il tuo post. Anch'io vorrei installare il 230 sulla mia TDR125R per avere più potenza. Rimango in attesa di tuoi cortesi aggiornamenti. Grazie